hi, in netback init mmap_pages, SetPageForeign(page, netif_page_release); that is, page->index = netif_page_release while netif_page_release is a function. so what''s the meaning of SetPageForeign? And when the function netif_page_release() will be called? thanks in advance. Zang Hongyong zanghongyong@ncic.ac.cn 2008-06-15 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> hi, > in netback init mmap_pages, > SetPageForeign(page, netif_page_release); > that is, page->index = netif_page_release > while netif_page_release is a function.netif_page_release is a function, and therefore: page->index = netif_page_release will store netif_page_release function pointer in ''index''> so what''s the meaning of SetPageForeign?Setting a page foreign means that the page is owned by another domain, and that some care needs to be taken when freeing it.> And when the function netif_page_release() will be called?Whenever PageForeignDestructor is called (as it calls the destructor function stored in the ''index'' field). PageForeignDestructor is called from: __free_pages_ok and free_hot_cold_page Hope this helps. Cheers Gr(z)egor(z) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Many thanks! And that is, when tx, after the data page is sent by native Nic driver in dom0, the data page will be freed, then netif_page_release() called which indicates netback to unmap the page offered by domU, and moves on its tx response. Is that so? If so, how about a bad NIC driver which doen't call free_page() after sending data out of machine ? and Why mmap_pages is allocated by alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ?? Forgive my silly questions above please. ======= 2008-06-18 18:52:27 您在来信中写道：======>> hi, >> in netback init mmap_pages, >> SetPageForeign(page, netif_page_release); >> that is, page->index = netif_page_release >> while netif_page_release is a function. > >netif_page_release is a function, and therefore: >page->index = netif_page_release >will store netif_page_release function pointer in 'index' > >> so what's the meaning of SetPageForeign? > >Setting a page foreign means that the page is owned by another domain, >and that some care needs to be taken when freeing it. > >> And when the function netif_page_release() will be called? > >Whenever PageForeignDestructor is called (as it calls the destructor >function stored in the 'index' field). >PageForeignDestructor is called from: >__free_pages_ok >and >free_hot_cold_page > >Hope this helps. > >Cheers >Gr(z)egor(z) > >_______________________________________________ >Xen-devel mailing list >Xen-devel@lists.xensource.com >http://lists.xensource.com/xen-devel > >= = = = = = = = = = = = = = = = = = = Zang Hongyong zanghongyong@ncic.ac.cn 2008-06-18 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> Many thanks! > And that is, when tx, after the data page is sent by native Nic driver in dom0, the data page will be freed, then netif_page_release() called which indicates netback to unmap the page offered by domU, and moves on its tx response. > > Is that so?Correct.> If so, how about a bad NIC driver which doen't call free_page() after sending data out of machine ?Well, it could happen if there was a memory leak in the driver. This would also be present in non-xenified linux. We are hoping for bug-free device drivers.> and Why mmap_pages is allocated by alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? > can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ??alloc_empty_pages_and_pagevec() balloons machine memory frames away from Dom0, you are therefore left with pseudo-physical page that's not backed by real memory. You want that, because you'll substitute DomU's memory frame in it's place. I don't think alloc_vm_area does that. It would only allocate virtually continuous range of memory. Cheers Gr(z)egor(z)> > Forgive my silly questions above please. > > > ======= 2008-06-18 18:52:27 您在来信中写道：======> >>> hi, >>> in netback init mmap_pages, >>> SetPageForeign(page, netif_page_release); >>> that is, page->index = netif_page_release >>> while netif_page_release is a function. >> >>netif_page_release is a function, and therefore: >>page->index = netif_page_release >>will store netif_page_release function pointer in 'index' >> >>> so what's the meaning of SetPageForeign? >> >>Setting a page foreign means that the page is owned by another domain, >>and that some care needs to be taken when freeing it. >> >>> And when the function netif_page_release() will be called? >> >>Whenever PageForeignDestructor is called (as it calls the destructor >>function stored in the 'index' field). >>PageForeignDestructor is called from: >>__free_pages_ok >>and >>free_hot_cold_page >> >>Hope this helps. >> >>Cheers >>Gr(z)egor(z) >> >>_______________________________________________ >>Xen-devel mailing list >>Xen-devel@lists.xensource.com >>http://lists.xensource.com/xen-devel >> >> > > = = = = = = = = = = = = = = = = = = = > Zang Hongyong > zanghongyong@ncic.ac.cn > 2008-06-18 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Thanks again! Another question about netback. tasklet is used in both tx and rx. Lets take a look at rx, Before tasklet, packets of all vnifs must be queued together, and in tasklet packet will be dequeued, and handled to its proper netfront of domU. 1)why not handle packet directly without the overall queue and tasklet stuff? 2)Is the overall queue and tasklet stuff fair to all vnifs? For example， when vif1.0 rx, the netback driver put its packet to overall queue and do tasklet, while in tasklet, packets belonging to other vif maybe handled. I've noticed when tx, netfront handle packet directly to its proper Ring,Request stuff. ======= 2008-06-19 00:37:40 您在来信中写道：======>> Many thanks! >> And that is, when tx, after the data page is sent by native Nic driver in dom0, the data page will be freed, then netif_page_release() called which indicates netback to unmap the page offered by domU, and moves on its tx response. >> >> Is that so? > >Correct. > >> If so, how about a bad NIC driver which doen't call free_page() after sending data out of machine ? > >Well, it could happen if there was a memory leak in the driver. This >would also be present in non-xenified linux. We are hoping for >bug-free device drivers. > > >> and Why mmap_pages is allocated by alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? >> can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ?? > >alloc_empty_pages_and_pagevec() balloons machine memory frames away >from Dom0, you are therefore left with pseudo-physical page that's not >backed by real memory. You want that, because you'll substitute DomU's >memory frame in it's place. I don't think alloc_vm_area does that. It >would only allocate virtually continuous range of memory. > >Cheers >Gr(z)egor(z) > >> >> Forgive my silly questions above please. >> >> >> ======= 2008-06-18 18:52:27 您在来信中写道：======>> >>>> hi, >>>> in netback init mmap_pages, >>>> SetPageForeign(page, netif_page_release); >>>> that is, page->index = netif_page_release >>>> while netif_page_release is a function. >>> >>>netif_page_release is a function, and therefore: >>>page->index = netif_page_release >>>will store netif_page_release function pointer in 'index' >>> >>>> so what's the meaning of SetPageForeign? >>> >>>Setting a page foreign means that the page is owned by another domain, >>>and that some care needs to be taken when freeing it. >>> >>>> And when the function netif_page_release() will be called? >>> >>>Whenever PageForeignDestructor is called (as it calls the destructor >>>function stored in the 'index' field). >>>PageForeignDestructor is called from: >>>__free_pages_ok >>>and >>>free_hot_cold_page >>> >>>Hope this helps. >>> >>>Cheers >>>Gr(z)egor(z) >>> >>>_______________________________________________ >>>Xen-devel mailing list >>>Xen-devel@lists.xensource.com >>>http://lists.xensource.com/xen-devel >>> >>> >> >> = = = = = = = = = = = = = = = = = = = >> Zang Hongyong >> zanghongyong@ncic.ac.cn >> 2008-06-18 >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> >> >_______________________________________________ >Xen-devel mailing list >Xen-devel@lists.xensource.com >http://lists.xensource.com/xen-devel >= = = = = = = = = = = = = = = = = = = Zang Hongyong zanghongyong@ncic.ac.cn 2008-06-19 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
The aim is to achieve batching and scheduling of work (to some extent) on both the transmit and receive paths. So no vif gets starved, and larger batches of packets are handled more efficiently. -- Keir On 19/6/08 01:40, "Zang Hongyong" <zanghongyong@ncic.ac.cn> wrote:> Thanks again! > Another question about netback. > tasklet is used in both tx and rx. Lets take a look at rx, Before tasklet, > packets of all vnifs must be queued together, and in tasklet packet will be > dequeued, and handled to its proper netfront of domU. > 1)why not handle packet directly without the overall queue and tasklet stuff? > 2)Is the overall queue and tasklet stuff fair to all vnifs? For example， when > vif1.0 rx, the netback driver put its packet to overall queue and do tasklet, > while in tasklet, packets belonging to other vif maybe handled. > I''ve noticed when tx, netfront handle packet directly to its proper > Ring,Request stuff. > > > > ======= 2008-06-19 00:37:40 您在来信中写道：======> >>> Many thanks! >>> And that is, when tx, after the data page is sent by native Nic driver in >>> dom0, the data page will be freed, then netif_page_release() called which >>> indicates netback to unmap the page offered by domU, and moves on its tx >>> response. >>> >>> Is that so? >> >> Correct. >> >>> If so, how about a bad NIC driver which doen''t call free_page() after >>> sending data out of machine ? >> >> Well, it could happen if there was a memory leak in the driver. This >> would also be present in non-xenified linux. We are hoping for >> bug-free device drivers. >> >> >>> and Why mmap_pages is allocated by >>> alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? >>> can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ?? >> >> alloc_empty_pages_and_pagevec() balloons machine memory frames away >> from Dom0, you are therefore left with pseudo-physical page that''s not >> backed by real memory. You want that, because you''ll substitute DomU''s >> memory frame in it''s place. I don''t think alloc_vm_area does that. It >> would only allocate virtually continuous range of memory. >> >> Cheers >> Gr(z)egor(z) >> >>> >>> Forgive my silly questions above please. >>> >>> >>> ======= 2008-06-18 18:52:27 您在来信中写道：======>>> >>>>> hi, >>>>> in netback init mmap_pages, >>>>> SetPageForeign(page, netif_page_release); >>>>> that is, page->index = netif_page_release >>>>> while netif_page_release is a function. >>>> >>>> netif_page_release is a function, and therefore: >>>> page->index = netif_page_release >>>> will store netif_page_release function pointer in ''index'' >>>> >>>>> so what''s the meaning of SetPageForeign? >>>> >>>> Setting a page foreign means that the page is owned by another domain, >>>> and that some care needs to be taken when freeing it. >>>> >>>>> And when the function netif_page_release() will be called? >>>> >>>> Whenever PageForeignDestructor is called (as it calls the destructor >>>> function stored in the ''index'' field). >>>> PageForeignDestructor is called from: >>>> __free_pages_ok >>>> and >>>> free_hot_cold_page >>>> >>>> Hope this helps. >>>> >>>> Cheers >>>> Gr(z)egor(z) >>>> >>>> _______________________________________________ >>>> Xen-devel mailing list >>>> Xen-devel@lists.xensource.com >>>> http://lists.xensource.com/xen-devel >>>> >>>> >>> >>> = = = = = = = = = = = = = = = = = = = >>> Zang Hongyong >>> zanghongyong@ncic.ac.cn >>> 2008-06-18 >>> >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >>> >>> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> > > = = = = = = = = = = = = = = = = = = = > Zang Hongyong > zanghongyong@ncic.ac.cn > 2008-06-19 > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
thanks. Maybe I understand.
Another question
In netback:
static inline void maybe_schedule_tx_action(void)
{
smp_mb();
if ((NR_PENDING_REQS < (MAX_PENDING_REQS/2)) &&
!list_empty(&net_schedule_list))
tasklet_schedule(&net_tx_tasklet);
}
... ...
while
#define NR_PENDING_REQS (MAX_PENDING_REQS - pending_prod + pending_cons)
that is NR_PENDING_REQS = MAX_PENDING_REQS - (pending_prod - pending_cons)
My question is when NR_PENDING_REQS cannot satisfy the above condition
"(NR_PENDING_REQS < (MAX_PENDING_REQS/2)"?
why not handle the condition of "NR_PENDING_REQS >=
(MAX_PENDING_REQS/2)"?
======= 2008-06-19 15:22:58 您在来信中写道：======>The aim is to achieve batching and scheduling of work (to some extent) on
>both the transmit and receive paths. So no vif gets starved, and larger
>batches of packets are handled more efficiently.
>
> -- Keir
>
>
>On 19/6/08 01:40, "Zang Hongyong" <zanghongyong@ncic.ac.cn>
wrote:
>
>> Thanks again!
>> Another question about netback.
>> tasklet is used in both tx and rx. Lets take a look at rx, Before
tasklet,
>> packets of all vnifs must be queued together, and in tasklet packet
will be
>> dequeued, and handled to its proper netfront of domU.
>> 1)why not handle packet directly without the overall queue and tasklet
stuff?
>> 2)Is the overall queue and tasklet stuff fair to all vnifs? For
example， when
>> vif1.0 rx, the netback driver put its packet to overall queue and do
tasklet,
>> while in tasklet, packets belonging to other vif maybe handled.
>> I've noticed when tx, netfront handle packet directly to its
proper
>> Ring,Request stuff.
>>
>>
>>
>> ======= 2008-06-19 00:37:40 您在来信中写道：======>>
>>>> Many thanks!
>>>> And that is, when tx, after the data page is sent by native Nic
driver in
>>>> dom0, the data page will be freed, then netif_page_release()
called which
>>>> indicates netback to unmap the page offered by domU, and moves
on its tx
>>>> response.
>>>>
>>>> Is that so?
>>>
>>> Correct.
>>>
>>>> If so, how about a bad NIC driver which doen't call
free_page() after
>>>> sending data out of machine ?
>>>
>>> Well, it could happen if there was a memory leak in the driver.
This
>>> would also be present in non-xenified linux. We are hoping for
>>> bug-free device drivers.
>>>
>>>
>>>> and Why mmap_pages is allocated by
>>>> alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)?
>>>> can mmap_pages be allocated by alloc_vm_area() and
vmalloc_to_page() ??
>>>
>>> alloc_empty_pages_and_pagevec() balloons machine memory frames away
>>> from Dom0, you are therefore left with pseudo-physical page
that's not
>>> backed by real memory. You want that, because you'll substitute
DomU's
>>> memory frame in it's place. I don't think alloc_vm_area
does that. It
>>> would only allocate virtually continuous range of memory.
>>>
>>> Cheers
>>> Gr(z)egor(z)
>>>
>>>>
>>>> Forgive my silly questions above please.
>>>>
>>>>
>>>> ======= 2008-06-18 18:52:27 您在来信中写道：======>>>>
>>>>>> hi,
>>>>>> in netback init mmap_pages,
>>>>>> SetPageForeign(page,
netif_page_release);
>>>>>> that is, page->index = netif_page_release
>>>>>> while netif_page_release is a function.
>>>>>
>>>>> netif_page_release is a function, and therefore:
>>>>> page->index = netif_page_release
>>>>> will store netif_page_release function pointer in
'index'
>>>>>
>>>>>> so what's the meaning of SetPageForeign?
>>>>>
>>>>> Setting a page foreign means that the page is owned by
another domain,
>>>>> and that some care needs to be taken when freeing it.
>>>>>
>>>>>> And when the function netif_page_release() will be
called?
>>>>>
>>>>> Whenever PageForeignDestructor is called (as it calls the
destructor
>>>>> function stored in the 'index' field).
>>>>> PageForeignDestructor is called from:
>>>>> __free_pages_ok
>>>>> and
>>>>> free_hot_cold_page
>>>>>
>>>>> Hope this helps.
>>>>>
>>>>> Cheers
>>>>> Gr(z)egor(z)
>>>>>
>>>>> _______________________________________________
>>>>> Xen-devel mailing list
>>>>> Xen-devel@lists.xensource.com
>>>>> http://lists.xensource.com/xen-devel
>>>>>
>>>>>
>>>>
>>>> = = = = = = = = = = = = = = = = = = = >>>> Zang
Hongyong
>>>> zanghongyong@ncic.ac.cn
>>>> 2008-06-18
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xensource.com
>>>> http://lists.xensource.com/xen-devel
>>>>
>>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xensource.com
>>> http://lists.xensource.com/xen-devel
>>>
>>
>> = = = = = = = = = = = = = = = = = = = >> Zang Hongyong
>> zanghongyong@ncic.ac.cn
>> 2008-06-19
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
>
>
>
>_______________________________________________
>Xen-devel mailing list
>Xen-devel@lists.xensource.com
>http://lists.xensource.com/xen-devel
= = = = = = = = = = = = = = = = = = = Zang Hongyong
zanghongyong@ncic.ac.cn
2008-06-22
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel
> thanks. Maybe I understand. > Another question > In netback: > static inline void maybe_schedule_tx_action(void) > { > smp_mb(); > if ((NR_PENDING_REQS < (MAX_PENDING_REQS/2)) && > !list_empty(&net_schedule_list)) > tasklet_schedule(&net_tx_tasklet); > } > ... ... > > while > #define NR_PENDING_REQS (MAX_PENDING_REQS - pending_prod + pending_cons) > that is NR_PENDING_REQS = MAX_PENDING_REQS - (pending_prod - pending_cons) > > My question is when NR_PENDING_REQS cannot satisfy the above condition "(NR_PENDING_REQS < (MAX_PENDING_REQS/2)"? > why not handle the condition of "NR_PENDING_REQS >= (MAX_PENDING_REQS/2)"?If there are many pending requests (more then MAX/2), new requests will have to wait on frontend-backend rings (a form of congestion control). When some of the pending requests get dealt with (and NR_PENDING_REQS falls below MAX/2) new ones will be accepted. Also, note that net_tx_tasklet doesn't only get scheduled by maybe_schedule_tx_action. There also is: - netbk_tx_pending_timeout: triggered by a timeout timer - netif_idx_release: triggered by a net data page being released The three net_tx_tasklet schedulers guarantee continuous flow of skbs out of netback. Cheers Gr(z)egor(z)> > > ======= 2008-06-19 15:22:58 您在来信中写道：======> >>The aim is to achieve batching and scheduling of work (to some extent) on >>both the transmit and receive paths. So no vif gets starved, and larger >>batches of packets are handled more efficiently. >> >> -- Keir >> >> >>On 19/6/08 01:40, "Zang Hongyong" <zanghongyong@ncic.ac.cn> wrote: >> >>> Thanks again! >>> Another question about netback. >>> tasklet is used in both tx and rx. Lets take a look at rx, Before tasklet, >>> packets of all vnifs must be queued together, and in tasklet packet will be >>> dequeued, and handled to its proper netfront of domU. >>> 1)why not handle packet directly without the overall queue and tasklet stuff? >>> 2)Is the overall queue and tasklet stuff fair to all vnifs? For example， when >>> vif1.0 rx, the netback driver put its packet to overall queue and do tasklet, >>> while in tasklet, packets belonging to other vif maybe handled. >>> I've noticed when tx, netfront handle packet directly to its proper >>> Ring,Request stuff. >>> >>> >>> >>> ======= 2008-06-19 00:37:40 您在来信中写道：======>>> >>>>> Many thanks! >>>>> And that is, when tx, after the data page is sent by native Nic driver in >>>>> dom0, the data page will be freed, then netif_page_release() called which >>>>> indicates netback to unmap the page offered by domU, and moves on its tx >>>>> response. >>>>> >>>>> Is that so? >>>> >>>> Correct. >>>> >>>>> If so, how about a bad NIC driver which doen't call free_page() after >>>>> sending data out of machine ? >>>> >>>> Well, it could happen if there was a memory leak in the driver. This >>>> would also be present in non-xenified linux. We are hoping for >>>> bug-free device drivers. >>>> >>>> >>>>> and Why mmap_pages is allocated by >>>>> alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? >>>>> can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ?? >>>> >>>> alloc_empty_pages_and_pagevec() balloons machine memory frames away >>>> from Dom0, you are therefore left with pseudo-physical page that's not >>>> backed by real memory. You want that, because you'll substitute DomU's >>>> memory frame in it's place. I don't think alloc_vm_area does that. It >>>> would only allocate virtually continuous range of memory. >>>> >>>> Cheers >>>> Gr(z)egor(z) >>>> >>>>> >>>>> Forgive my silly questions above please. >>>>> >>>>> >>>>> ======= 2008-06-18 18:52:27 您在来信中写道：======>>>>> >>>>>>> hi, >>>>>>> in netback init mmap_pages, >>>>>>> SetPageForeign(page, netif_page_release); >>>>>>> that is, page->index = netif_page_release >>>>>>> while netif_page_release is a function. >>>>>> >>>>>> netif_page_release is a function, and therefore: >>>>>> page->index = netif_page_release >>>>>> will store netif_page_release function pointer in 'index' >>>>>> >>>>>>> so what's the meaning of SetPageForeign? >>>>>> >>>>>> Setting a page foreign means that the page is owned by another domain, >>>>>> and that some care needs to be taken when freeing it. >>>>>> >>>>>>> And when the function netif_page_release() will be called? >>>>>> >>>>>> Whenever PageForeignDestructor is called (as it calls the destructor >>>>>> function stored in the 'index' field). >>>>>> PageForeignDestructor is called from: >>>>>> __free_pages_ok >>>>>> and >>>>>> free_hot_cold_page >>>>>> >>>>>> Hope this helps. >>>>>> >>>>>> Cheers >>>>>> Gr(z)egor(z) >>>>>> >>>>>> _______________________________________________ >>>>>> Xen-devel mailing list >>>>>> Xen-devel@lists.xensource.com >>>>>> http://lists.xensource.com/xen-devel >>>>>> >>>>>> >>>>> >>>>> = = = = = = = = = = = = = = = = = = = >>>>> Zang Hongyong >>>>> zanghongyong@ncic.ac.cn >>>>> 2008-06-18 >>>>> >>>>> >>>>> _______________________________________________ >>>>> Xen-devel mailing list >>>>> Xen-devel@lists.xensource.com >>>>> http://lists.xensource.com/xen-devel >>>>> >>>>> >>>> _______________________________________________ >>>> Xen-devel mailing list >>>> Xen-devel@lists.xensource.com >>>> http://lists.xensource.com/xen-devel >>>> >>> >>> = = = = = = = = = = = = = = = = = = = >>> Zang Hongyong >>> zanghongyong@ncic.ac.cn >>> 2008-06-19 >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >> >> >> >>_______________________________________________ >>Xen-devel mailing list >>Xen-devel@lists.xensource.com >>http://lists.xensource.com/xen-devel > > = = = = = = = = = = = = = = = = = = = > Zang Hongyong > zanghongyong@ncic.ac.cn > 2008-06-22 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Many thanks.
and netbk_tx_pending_timeout() is added since xen3.2. I've not found this
timer in xen3.1.
==================================what about another question:
In netback netif_be_start_xmit()
if (!netif->copying_receiver ||
((skb_headlen(skb) + offset_in_page(skb->data)) >= PAGE_SIZE)) {
struct sk_buff *nskb = netbk_copy_skb(skb);
which calls skb_copy_bits()
it means when rx-flip, the skb data and frags are copied to another buffer.
then the buffer flip with domU's pages.
so before page flip with domU, copying happens in dom0. Does rx-flip make any
sense?
======= 2008-06-23 19:22:37 您在来信中写道：======>> thanks. Maybe I understand.
>> Another question
>> In netback:
>> static inline void maybe_schedule_tx_action(void)
>> {
>> smp_mb();
>> if ((NR_PENDING_REQS < (MAX_PENDING_REQS/2)) &&
>> !list_empty(&net_schedule_list))
>> tasklet_schedule(&net_tx_tasklet);
>> }
>> ... ...
>>
>> while
>> #define NR_PENDING_REQS (MAX_PENDING_REQS - pending_prod +
pending_cons)
>> that is NR_PENDING_REQS = MAX_PENDING_REQS - (pending_prod -
pending_cons)
>>
>> My question is when NR_PENDING_REQS cannot satisfy the above condition
"(NR_PENDING_REQS < (MAX_PENDING_REQS/2)"?
>> why not handle the condition of "NR_PENDING_REQS >=
(MAX_PENDING_REQS/2)"?
>
>If there are many pending requests (more then MAX/2), new requests
>will have to wait on frontend-backend rings (a form of congestion
>control). When some of the pending requests get dealt with (and
>NR_PENDING_REQS falls below MAX/2) new ones will be accepted.
>
>Also, note that net_tx_tasklet doesn't only get scheduled by
>maybe_schedule_tx_action. There also is:
>- netbk_tx_pending_timeout: triggered by a timeout timer
>- netif_idx_release: triggered by a net data page being released
>The three net_tx_tasklet schedulers guarantee continuous flow of skbs
>out of netback.
>
>Cheers
>Gr(z)egor(z)
>
>
>>
>>
>> ======= 2008-06-19 15:22:58 您在来信中写道：======>>
>>>The aim is to achieve batching and scheduling of work (to some
extent) on
>>>both the transmit and receive paths. So no vif gets starved, and
larger
>>>batches of packets are handled more efficiently.
>>>
>>> -- Keir
>>>
>>>
>>>On 19/6/08 01:40, "Zang Hongyong"
<zanghongyong@ncic.ac.cn> wrote:
>>>
>>>> Thanks again!
>>>> Another question about netback.
>>>> tasklet is used in both tx and rx. Lets take a look at rx,
Before tasklet,
>>>> packets of all vnifs must be queued together, and in tasklet
packet will be
>>>> dequeued, and handled to its proper netfront of domU.
>>>> 1)why not handle packet directly without the overall queue and
tasklet stuff?
>>>> 2)Is the overall queue and tasklet stuff fair to all vnifs? For
example， when
>>>> vif1.0 rx, the netback driver put its packet to overall queue
and do tasklet,
>>>> while in tasklet, packets belonging to other vif maybe handled.
>>>> I've noticed when tx, netfront handle packet directly to
its proper
>>>> Ring,Request stuff.
>>>>
>>>>
>>>>
>>>> ======= 2008-06-19 00:37:40 您在来信中写道：======>>>>
>>>>>> Many thanks!
>>>>>> And that is, when tx, after the data page is sent by
native Nic driver in
>>>>>> dom0, the data page will be freed, then
netif_page_release() called which
>>>>>> indicates netback to unmap the page offered by domU,
and moves on its tx
>>>>>> response.
>>>>>>
>>>>>> Is that so?
>>>>>
>>>>> Correct.
>>>>>
>>>>>> If so, how about a bad NIC driver which doen't call
free_page() after
>>>>>> sending data out of machine ?
>>>>>
>>>>> Well, it could happen if there was a memory leak in the
driver. This
>>>>> would also be present in non-xenified linux. We are hoping
for
>>>>> bug-free device drivers.
>>>>>
>>>>>
>>>>>> and Why mmap_pages is allocated by
>>>>>> alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)?
>>>>>> can mmap_pages be allocated by alloc_vm_area() and
vmalloc_to_page() ??
>>>>>
>>>>> alloc_empty_pages_and_pagevec() balloons machine memory
frames away
>>>>> from Dom0, you are therefore left with pseudo-physical page
that's not
>>>>> backed by real memory. You want that, because you'll
substitute DomU's
>>>>> memory frame in it's place. I don't think
alloc_vm_area does that. It
>>>>> would only allocate virtually continuous range of memory.
>>>>>
>>>>> Cheers
>>>>> Gr(z)egor(z)
>>>>>
>>>>>>
>>>>>> Forgive my silly questions above please.
>>>>>>
>>>>>>
>>>>>> ======= 2008-06-18 18:52:27
您在来信中写道：======>>>>>>
>>>>>>>> hi,
>>>>>>>> in netback init mmap_pages,
>>>>>>>> SetPageForeign(page,
netif_page_release);
>>>>>>>> that is, page->index = netif_page_release
>>>>>>>> while netif_page_release is a function.
>>>>>>>
>>>>>>> netif_page_release is a function, and therefore:
>>>>>>> page->index = netif_page_release
>>>>>>> will store netif_page_release function pointer in
'index'
>>>>>>>
>>>>>>>> so what's the meaning of SetPageForeign?
>>>>>>>
>>>>>>> Setting a page foreign means that the page is owned
by another domain,
>>>>>>> and that some care needs to be taken when freeing
it.
>>>>>>>
>>>>>>>> And when the function netif_page_release()
will be called?
>>>>>>>
>>>>>>> Whenever PageForeignDestructor is called (as it
calls the destructor
>>>>>>> function stored in the 'index' field).
>>>>>>> PageForeignDestructor is called from:
>>>>>>> __free_pages_ok
>>>>>>> and
>>>>>>> free_hot_cold_page
>>>>>>>
>>>>>>> Hope this helps.
>>>>>>>
>>>>>>> Cheers
>>>>>>> Gr(z)egor(z)
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Xen-devel mailing list
>>>>>>> Xen-devel@lists.xensource.com
>>>>>>> http://lists.xensource.com/xen-devel
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> = = = = = = = = = = = = = = = = = = =
>>>>>> Zang Hongyong
>>>>>> zanghongyong@ncic.ac.cn
>>>>>> 2008-06-18
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Xen-devel mailing list
>>>>>> Xen-devel@lists.xensource.com
>>>>>> http://lists.xensource.com/xen-devel
>>>>>>
>>>>>>
>>>>> _______________________________________________
>>>>> Xen-devel mailing list
>>>>> Xen-devel@lists.xensource.com
>>>>> http://lists.xensource.com/xen-devel
>>>>>
>>>>
>>>> = = = = = = = = = = = = = = = = = = = >>>> Zang
Hongyong
>>>> zanghongyong@ncic.ac.cn
>>>> 2008-06-19
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xensource.com
>>>> http://lists.xensource.com/xen-devel
>>>
>>>
>>>
>>>_______________________________________________
>>>Xen-devel mailing list
>>>Xen-devel@lists.xensource.com
>>>http://lists.xensource.com/xen-devel
>>
>> = = = = = = = = = = = = = = = = = = = >> Zang Hongyong
>> zanghongyong@ncic.ac.cn
>> 2008-06-22
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
>>
>>
>_______________________________________________
>Xen-devel mailing list
>Xen-devel@lists.xensource.com
>http://lists.xensource.com/xen-devel
>
= = = = = = = = = = = = = = = = = = = Zang Hongyong
zanghongyong@ncic.ac.cn
2008-06-23
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel
> what about another question: > > In netback netif_be_start_xmit() > if (!netif->copying_receiver || > ((skb_headlen(skb) + offset_in_page(skb->data)) >= PAGE_SIZE)) { > struct sk_buff *nskb = netbk_copy_skb(skb); > which calls skb_copy_bits() > > it means when rx-flip, the skb data and frags are copied to another buffer. > then the buffer flip with domU's pages. > so before page flip with domU, copying happens in dom0. Does rx-flip make any sense?The reason why you have to copy is to make sure that you pull the skb into a fresh page (which doesn't have any other pieces of data in it). It's only then that you can flip it to DomU. It used to be the case that the backend was more efficient in the rx-flip mode. Some/most skbs copies were avoided by keeping a close eye on the skb allocation. Since rx-flip is now only/mostly kept for backward compatibility (rx-copy is the default) the code was simplified. Note: with grant table copy you can ask the hypervisor to copy sub-page regions (in our case you can match the size of the skb) Cheers Gr(z)egor(z)> > > > ======= 2008-06-23 19:22:37 您在来信中写道：======> >>> thanks. Maybe I understand. >>> Another question >>> In netback: >>> static inline void maybe_schedule_tx_action(void) >>> { >>> smp_mb(); >>> if ((NR_PENDING_REQS < (MAX_PENDING_REQS/2)) && >>> !list_empty(&net_schedule_list)) >>> tasklet_schedule(&net_tx_tasklet); >>> } >>> ... ... >>> >>> while >>> #define NR_PENDING_REQS (MAX_PENDING_REQS - pending_prod + pending_cons) >>> that is NR_PENDING_REQS = MAX_PENDING_REQS - (pending_prod - pending_cons) >>> >>> My question is when NR_PENDING_REQS cannot satisfy the above condition "(NR_PENDING_REQS < (MAX_PENDING_REQS/2)"? >>> why not handle the condition of "NR_PENDING_REQS >= (MAX_PENDING_REQS/2)"? >> >>If there are many pending requests (more then MAX/2), new requests >>will have to wait on frontend-backend rings (a form of congestion >>control). When some of the pending requests get dealt with (and >>NR_PENDING_REQS falls below MAX/2) new ones will be accepted. >> >>Also, note that net_tx_tasklet doesn't only get scheduled by >>maybe_schedule_tx_action. There also is: >>- netbk_tx_pending_timeout: triggered by a timeout timer >>- netif_idx_release: triggered by a net data page being released >>The three net_tx_tasklet schedulers guarantee continuous flow of skbs >>out of netback. >> >>Cheers >>Gr(z)egor(z) >> >> >>> >>> >>> ======= 2008-06-19 15:22:58 您在来信中写道：======>>> >>>>The aim is to achieve batching and scheduling of work (to some extent) on >>>>both the transmit and receive paths. So no vif gets starved, and larger >>>>batches of packets are handled more efficiently. >>>> >>>> -- Keir >>>> >>>> >>>>On 19/6/08 01:40, "Zang Hongyong" <zanghongyong@ncic.ac.cn> wrote: >>>> >>>>> Thanks again! >>>>> Another question about netback. >>>>> tasklet is used in both tx and rx. Lets take a look at rx, Before tasklet, >>>>> packets of all vnifs must be queued together, and in tasklet packet will be >>>>> dequeued, and handled to its proper netfront of domU. >>>>> 1)why not handle packet directly without the overall queue and tasklet stuff? >>>>> 2)Is the overall queue and tasklet stuff fair to all vnifs? For example， when >>>>> vif1.0 rx, the netback driver put its packet to overall queue and do tasklet, >>>>> while in tasklet, packets belonging to other vif maybe handled. >>>>> I've noticed when tx, netfront handle packet directly to its proper >>>>> Ring,Request stuff. >>>>> >>>>> >>>>> >>>>> ======= 2008-06-19 00:37:40 您在来信中写道：======>>>>> >>>>>>> Many thanks! >>>>>>> And that is, when tx, after the data page is sent by native Nic driver in >>>>>>> dom0, the data page will be freed, then netif_page_release() called which >>>>>>> indicates netback to unmap the page offered by domU, and moves on its tx >>>>>>> response. >>>>>>> >>>>>>> Is that so? >>>>>> >>>>>> Correct. >>>>>> >>>>>>> If so, how about a bad NIC driver which doen't call free_page() after >>>>>>> sending data out of machine ? >>>>>> >>>>>> Well, it could happen if there was a memory leak in the driver. This >>>>>> would also be present in non-xenified linux. We are hoping for >>>>>> bug-free device drivers. >>>>>> >>>>>> >>>>>>> and Why mmap_pages is allocated by >>>>>>> alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? >>>>>>> can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ?? >>>>>> >>>>>> alloc_empty_pages_and_pagevec() balloons machine memory frames away >>>>>> from Dom0, you are therefore left with pseudo-physical page that's not >>>>>> backed by real memory. You want that, because you'll substitute DomU's >>>>>> memory frame in it's place. I don't think alloc_vm_area does that. It >>>>>> would only allocate virtually continuous range of memory. >>>>>> >>>>>> Cheers >>>>>> Gr(z)egor(z) >>>>>> >>>>>>> >>>>>>> Forgive my silly questions above please. >>>>>>> >>>>>>> >>>>>>> ======= 2008-06-18 18:52:27 您在来信中写道：======>>>>>>> >>>>>>>>> hi, >>>>>>>>> in netback init mmap_pages, >>>>>>>>> SetPageForeign(page, netif_page_release); >>>>>>>>> that is, page->index = netif_page_release >>>>>>>>> while netif_page_release is a function. >>>>>>>> >>>>>>>> netif_page_release is a function, and therefore: >>>>>>>> page->index = netif_page_release >>>>>>>> will store netif_page_release function pointer in 'index' >>>>>>>> >>>>>>>>> so what's the meaning of SetPageForeign? >>>>>>>> >>>>>>>> Setting a page foreign means that the page is owned by another domain, >>>>>>>> and that some care needs to be taken when freeing it. >>>>>>>> >>>>>>>>> And when the function netif_page_release() will be called? >>>>>>>> >>>>>>>> Whenever PageForeignDestructor is called (as it calls the destructor >>>>>>>> function stored in the 'index' field). >>>>>>>> PageForeignDestructor is called from: >>>>>>>> __free_pages_ok >>>>>>>> and >>>>>>>> free_hot_cold_page >>>>>>>> >>>>>>>> Hope this helps. >>>>>>>> >>>>>>>> Cheers >>>>>>>> Gr(z)egor(z) >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> Xen-devel mailing list >>>>>>>> Xen-devel@lists.xensource.com >>>>>>>> http://lists.xensource.com/xen-devel >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> = = = = = = = = = = = = = = = = = = = >>>>>>> Zang Hongyong >>>>>>> zanghongyong@ncic.ac.cn >>>>>>> 2008-06-18 >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> Xen-devel mailing list >>>>>>> Xen-devel@lists.xensource.com >>>>>>> http://lists.xensource.com/xen-devel >>>>>>> >>>>>>> >>>>>> _______________________________________________ >>>>>> Xen-devel mailing list >>>>>> Xen-devel@lists.xensource.com >>>>>> http://lists.xensource.com/xen-devel >>>>>> >>>>> >>>>> = = = = = = = = = = = = = = = = = = = >>>>> Zang Hongyong >>>>> zanghongyong@ncic.ac.cn >>>>> 2008-06-19 >>>>> >>>>> _______________________________________________ >>>>> Xen-devel mailing list >>>>> Xen-devel@lists.xensource.com >>>>> http://lists.xensource.com/xen-devel >>>> >>>> >>>> >>>>_______________________________________________ >>>>Xen-devel mailing list >>>>Xen-devel@lists.xensource.com >>>>http://lists.xensource.com/xen-devel >>> >>> = = = = = = = = = = = = = = = = = = = >>> Zang Hongyong >>> zanghongyong@ncic.ac.cn >>> 2008-06-22 >>> >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >>> >>> >>_______________________________________________ >>Xen-devel mailing list >>Xen-devel@lists.xensource.com >>http://lists.xensource.com/xen-devel >> > > = = = = = = = = = = = = = = = = = = = > Zang Hongyong > zanghongyong@ncic.ac.cn > 2008-06-23 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
======= 2008-06-24 07:21:28 您在来信中写道：======>> what about another question: >> >> In netback netif_be_start_xmit() >> if (!netif->copying_receiver || >> ((skb_headlen(skb) + offset_in_page(skb->data)) >= PAGE_SIZE)) { >> struct sk_buff *nskb = netbk_copy_skb(skb); >> which calls skb_copy_bits() >> >> it means when rx-flip, the skb data and frags are copied to another buffer. >> then the buffer flip with domU's pages. >> so before page flip with domU, copying happens in dom0. Does rx-flip make any sense? > >The reason why you have to copy is to make sure that you pull the skb >into a fresh page (which doesn't have any other pieces of data in it). >It's only then that you can flip it to DomU. >It used to be the case that the backend was more efficient in the >rx-flip mode. Some/most skbs copies were avoided by keeping a close >eye on the skb allocation. Since rx-flip is now only/mostly kept for >backward compatibility (rx-copy is the default) the code was >simplified.You mean in previous Xen release, rx-flip is more efficient than today's release. And keeping rx-flip in Xen Source Code tree today is only for compatibility. So no need to do more optimizing for it. Is my understanding right?>Note: with grant table copy you can ask the hypervisor to copy >sub-page regions (in our case you can match the size of the skb) > >Cheers >Gr(z)egor(z) >> >> >> >> ======= 2008-06-23 19:22:37 您在来信中写道：======>> >>>> thanks. Maybe I understand. >>>> Another question >>>> In netback: >>>> static inline void maybe_schedule_tx_action(void) >>>> { >>>> smp_mb(); >>>> if ((NR_PENDING_REQS < (MAX_PENDING_REQS/2)) && >>>> !list_empty(&net_schedule_list)) >>>> tasklet_schedule(&net_tx_tasklet); >>>> } >>>> ... ... >>>> >>>> while >>>> #define NR_PENDING_REQS (MAX_PENDING_REQS - pending_prod + pending_cons) >>>> that is NR_PENDING_REQS = MAX_PENDING_REQS - (pending_prod - pending_cons) >>>> >>>> My question is when NR_PENDING_REQS cannot satisfy the above condition "(NR_PENDING_REQS < (MAX_PENDING_REQS/2)"? >>>> why not handle the condition of "NR_PENDING_REQS >= (MAX_PENDING_REQS/2)"? >>> >>>If there are many pending requests (more then MAX/2), new requests >>>will have to wait on frontend-backend rings (a form of congestion >>>control). When some of the pending requests get dealt with (and >>>NR_PENDING_REQS falls below MAX/2) new ones will be accepted. >>> >>>Also, note that net_tx_tasklet doesn't only get scheduled by >>>maybe_schedule_tx_action. There also is: >>>- netbk_tx_pending_timeout: triggered by a timeout timer >>>- netif_idx_release: triggered by a net data page being released >>>The three net_tx_tasklet schedulers guarantee continuous flow of skbs >>>out of netback. >>> >>>Cheers >>>Gr(z)egor(z) >>> >>> >>>> >>>> >>>> ======= 2008-06-19 15:22:58 您在来信中写道：======>>>> >>>>>The aim is to achieve batching and scheduling of work (to some extent) on >>>>>both the transmit and receive paths. So no vif gets starved, and larger >>>>>batches of packets are handled more efficiently. >>>>> >>>>> -- Keir >>>>> >>>>> >>>>>On 19/6/08 01:40, "Zang Hongyong" <zanghongyong@ncic.ac.cn> wrote: >>>>> >>>>>> Thanks again! >>>>>> Another question about netback. >>>>>> tasklet is used in both tx and rx. Lets take a look at rx, Before tasklet, >>>>>> packets of all vnifs must be queued together, and in tasklet packet will be >>>>>> dequeued, and handled to its proper netfront of domU. >>>>>> 1)why not handle packet directly without the overall queue and tasklet stuff? >>>>>> 2)Is the overall queue and tasklet stuff fair to all vnifs? For example， when >>>>>> vif1.0 rx, the netback driver put its packet to overall queue and do tasklet, >>>>>> while in tasklet, packets belonging to other vif maybe handled. >>>>>> I've noticed when tx, netfront handle packet directly to its proper >>>>>> Ring,Request stuff. >>>>>> >>>>>> >>>>>> >>>>>> ======= 2008-06-19 00:37:40 您在来信中写道：======>>>>>> >>>>>>>> Many thanks! >>>>>>>> And that is, when tx, after the data page is sent by native Nic driver in >>>>>>>> dom0, the data page will be freed, then netif_page_release() called which >>>>>>>> indicates netback to unmap the page offered by domU, and moves on its tx >>>>>>>> response. >>>>>>>> >>>>>>>> Is that so? >>>>>>> >>>>>>> Correct. >>>>>>> >>>>>>>> If so, how about a bad NIC driver which doen't call free_page() after >>>>>>>> sending data out of machine ? >>>>>>> >>>>>>> Well, it could happen if there was a memory leak in the driver. This >>>>>>> would also be present in non-xenified linux. We are hoping for >>>>>>> bug-free device drivers. >>>>>>> >>>>>>> >>>>>>>> and Why mmap_pages is allocated by >>>>>>>> alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)? >>>>>>>> can mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ?? >>>>>>> >>>>>>> alloc_empty_pages_and_pagevec() balloons machine memory frames away >>>>>>> from Dom0, you are therefore left with pseudo-physical page that's not >>>>>>> backed by real memory. You want that, because you'll substitute DomU's >>>>>>> memory frame in it's place. I don't think alloc_vm_area does that. It >>>>>>> would only allocate virtually continuous range of memory. >>>>>>> >>>>>>> Cheers >>>>>>> Gr(z)egor(z) >>>>>>> >>>>>>>> >>>>>>>> Forgive my silly questions above please. >>>>>>>> >>>>>>>> >>>>>>>> ======= 2008-06-18 18:52:27 您在来信中写道：======>>>>>>>> >>>>>>>>>> hi, >>>>>>>>>> in netback init mmap_pages, >>>>>>>>>> SetPageForeign(page, netif_page_release); >>>>>>>>>> that is, page->index = netif_page_release >>>>>>>>>> while netif_page_release is a function. >>>>>>>>> >>>>>>>>> netif_page_release is a function, and therefore: >>>>>>>>> page->index = netif_page_release >>>>>>>>> will store netif_page_release function pointer in 'index' >>>>>>>>> >>>>>>>>>> so what's the meaning of SetPageForeign? >>>>>>>>> >>>>>>>>> Setting a page foreign means that the page is owned by another domain, >>>>>>>>> and that some care needs to be taken when freeing it. >>>>>>>>> >>>>>>>>>> And when the function netif_page_release() will be called? >>>>>>>>> >>>>>>>>> Whenever PageForeignDestructor is called (as it calls the destructor >>>>>>>>> function stored in the 'index' field). >>>>>>>>> PageForeignDestructor is called from: >>>>>>>>> __free_pages_ok >>>>>>>>> and >>>>>>>>> free_hot_cold_page >>>>>>>>> >>>>>>>>> Hope this helps. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> Gr(z)egor(z) >>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> Xen-devel mailing list >>>>>>>>> Xen-devel@lists.xensource.com >>>>>>>>> http://lists.xensource.com/xen-devel >>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>>> = = = = = = = = = = = = = = = = = = = >>>>>>>> Zang Hongyong >>>>>>>> zanghongyong@ncic.ac.cn >>>>>>>> 2008-06-18 >>>>>>>> >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> Xen-devel mailing list >>>>>>>> Xen-devel@lists.xensource.com >>>>>>>> http://lists.xensource.com/xen-devel >>>>>>>> >>>>>>>> >>>>>>> _______________________________________________ >>>>>>> Xen-devel mailing list >>>>>>> Xen-devel@lists.xensource.com >>>>>>> http://lists.xensource.com/xen-devel >>>>>>> >>>>>> >>>>>> = = = = = = = = = = = = = = = = = = = >>>>>> Zang Hongyong >>>>>> zanghongyong@ncic.ac.cn >>>>>> 2008-06-19 >>>>>> >>>>>> _______________________________________________ >>>>>> Xen-devel mailing list >>>>>> Xen-devel@lists.xensource.com >>>>>> http://lists.xensource.com/xen-devel >>>>> >>>>> >>>>> >>>>>_______________________________________________ >>>>>Xen-devel mailing list >>>>>Xen-devel@lists.xensource.com >>>>>http://lists.xensource.com/xen-devel >>>> >>>> = = = = = = = = = = = = = = = = = = = >>>> Zang Hongyong >>>> zanghongyong@ncic.ac.cn >>>> 2008-06-22 >>>> >>>> >>>> _______________________________________________ >>>> Xen-devel mailing list >>>> Xen-devel@lists.xensource.com >>>> http://lists.xensource.com/xen-devel >>>> >>>> >>>_______________________________________________ >>>Xen-devel mailing list >>>Xen-devel@lists.xensource.com >>>http://lists.xensource.com/xen-devel >>> >> >> = = = = = = = = = = = = = = = = = = = >> Zang Hongyong >> zanghongyong@ncic.ac.cn >> 2008-06-23 >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> >> >_______________________________________________ >Xen-devel mailing list >Xen-devel@lists.xensource.com >http://lists.xensource.com/xen-devel >= = = = = = = = = = = = = = = = = = = Zang Hongyong zanghongyong@ncic.ac.cn 2008-06-24 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Grzegorz Miłoś
2008-Jun-24 06:41 UTC
Re: Re: Re: Re: [Xen-devel] SetPageForeign in netback
>>The reason why you have to copy is to make sure that you pull the skb >>into a fresh page (which doesn''t have any other pieces of data in it). >>It''s only then that you can flip it to DomU. >>It used to be the case that the backend was more efficient in the >>rx-flip mode. Some/most skbs copies were avoided by keeping a close >>eye on the skb allocation. Since rx-flip is now only/mostly kept for >>backward compatibility (rx-copy is the default) the code was >>simplified. > > You mean in previous Xen release, rx-flip is more efficient than today''s release. And keeping rx-flip in Xen Source Code tree today is only for compatibility. So no need to do more optimizing for it. > Is my understanding right? >I don''t know if much performance was lost (the code got simplified, at the expense of potentially more skb copies, but I don''t know of any experimental tests to benchmark what the effect was exactly), but aside from that, your understanding is correct. Cheers Gr(z)egor(z) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Zang Hongyong
2008-Jun-25 00:50 UTC
Re: Re: Re: Re: Re: [Xen-devel] SetPageForeign in netback
Thanks a lot. I noticed that the plug-in accelerator is available in Xen3.2 Source code. The accelerator is used for direct IO network devices such as Infiniband and Solarflare 10G Nic. Can it be used for the PCIE IOV devices? and is there any referece implementation of PCIE IOV Nics now? ======= 2008-06-24 14:41:49 您在来信中写道：======>>>The reason why you have to copy is to make sure that you pull the skb >>>into a fresh page (which doesn't have any other pieces of data in it). >>>It's only then that you can flip it to DomU. >>>It used to be the case that the backend was more efficient in the >>>rx-flip mode. Some/most skbs copies were avoided by keeping a close >>>eye on the skb allocation. Since rx-flip is now only/mostly kept for >>>backward compatibility (rx-copy is the default) the code was >>>simplified. >> >> You mean in previous Xen release, rx-flip is more efficient than today's release. And keeping rx-flip in Xen Source Code tree today is only for compatibility. So no need to do more optimizing for it. >> Is my understanding right? >> > >I don't know if much performance was lost (the code got simplified, at >the expense of potentially more skb copies, but I don't know of any >experimental tests to benchmark what the effect was exactly), but >aside from that, your understanding is correct. > >Cheers >Gr(z)egor(z) > >_______________________________________________ >Xen-devel mailing list >Xen-devel@lists.xensource.com >http://lists.xensource.com/xen-devel > >= = = = = = = = = = = = = = = = = = = Zang Hongyong zanghongyong@ncic.ac.cn 2008-06-25 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi Zang, You wrote:> I noticed that the plug-in accelerator is available in Xen3.2 Source code. The > accelerator is used for direct IO network devices such as Infiniband and > Solarflare 10G Nic. > Can it be used for the PCIE IOV devices? > and is there any referece implementation of PCIE IOV Nics now?The accelerator plug-in framework is designed to be general-purpose, so it should work fine with IOV devices. It requires a plug-in driver to be written for both netfront and netback. Between them, these drivers will need to ensure that BAR pages are mapped into the guest, IOMMU page tables are setup and interrupts passed to the guest. These jobs are outside the scope of the accelerator framework which is just concerned with handing over traffic from netfront/netback. I don''t know of a reference implementation of an IOV NIC - just the Solarflare one, but the PCI passthrough code should help you with mapping interrupts and pages. Which NIC are you wanting to use? Cheers, Neil. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel