Xu, Dongxiao
2009-Sep-30 18:17 UTC
[Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
Patch the Xen version of ring.h
Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
diff -r 8fc927798476 xen/include/public/io/ring.h
--- a/xen/include/public/io/ring.h Tue Sep 01 11:36:51 2009 +0100
+++ b/xen/include/public/io/ring.h Thu Oct 01 02:11:45 2009 +0800
@@ -97,7 +97,8 @@ struct __name##_sring {
struct __name##_sring { \
RING_IDX req_prod, req_event; \
RING_IDX rsp_prod, rsp_event; \
- uint8_t pad[48]; \
+ uint8_t netfront_smartpoll_active; \
+ uint8_t pad[47]; \
union __name##_sring_entry ring[1]; /* variable-length */ \
}; \
\
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Xu, Dongxiao
2009-Oct-01 00:22 UTC
[Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
Resend and put the patch in attachment.
Patch the Xen version of ring.h
Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
diff -r 8fc927798476 xen/include/public/io/ring.h
--- a/xen/include/public/io/ring.h Tue Sep 01 11:36:51 2009 +0100
+++ b/xen/include/public/io/ring.h Thu Oct 01 02:11:45 2009 +0800
@@ -97,7 +97,8 @@ struct __name##_sring {
struct __name##_sring { \
RING_IDX req_prod, req_event; \
RING_IDX rsp_prod, rsp_event; \
- uint8_t pad[48]; \
+ uint8_t netfront_smartpoll_active; \
+ uint8_t pad[47]; \
union __name##_sring_entry ring[1]; /* variable-length */ \
}; \
\
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Ian Campbell
2009-Oct-01 10:03 UTC
Re: [Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
You are adding a netfront specific field to the generic ring structure? That seems rather ugly. Is this even necessary as a piece of shared state? Once netback and netfront have agreed, via xenstore, to use the feature netback seems to set the flag every time it would have previously notified netfront. Ian. On Thu, 2009-10-01 at 01:22 +0100, Xu, Dongxiao wrote:> Resend and put the patch in attachment. > > Patch the Xen version of ring.h > > Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com> > > diff -r 8fc927798476 xen/include/public/io/ring.h > --- a/xen/include/public/io/ring.h Tue Sep 01 11:36:51 2009 +0100 > +++ b/xen/include/public/io/ring.h Thu Oct 01 02:11:45 2009 +0800 > @@ -97,7 +97,8 @@ struct __name##_sring { > struct __name##_sring { \ > RING_IDX req_prod, req_event; \ > RING_IDX rsp_prod, rsp_event; \ > - uint8_t pad[48]; \ > + uint8_t netfront_smartpoll_active; \ > + uint8_t pad[47]; \ > union __name##_sring_entry ring[1]; /* variable-length */ \ > }; \ > \ > _______________________________________________ > 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
Xu, Dongxiao
2009-Oct-01 14:02 UTC
RE: [Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
We found that the event notification frequency is still high in some network
cases. NAPI polls only for a little
time slot and does not efficient enough in our backend/frontend case. Actually
our patch repeated calling NAPI
interface to do more polling, and netback will NOT notify netfront during this
period. Once netfront polling out
all the data, and finds that there is no more data arrive/send during the next
100ms, the timer will stop working
to end the polling.
This filed ''smart_poll_active'' is shared by netfront and
netback, to indicate whether netfront is polling data.
So this filed is necessary for netback to notify netfront if this flag is not
set.
This field is different from the flag in xenstore, which indicates whether
other-end has this new feature. If other-end doesn''t support the new
feature, everything goes in the original way.
Thanks!
Dongxiao
________________________________________
From: Ian Campbell [Ian.Campbell@citrix.com]
Sent: Thursday, October 01, 2009 3:03 AM
To: Xu, Dongxiao
Cc: xen-devel@lists.xensource.com; Keir Fraser
Subject: Re: [Xen-devel][PATCH] VNIF: Using smart polling instead of event
notification.
You are adding a netfront specific field to the generic ring structure?
That seems rather ugly.
Is this even necessary as a piece of shared state? Once netback and
netfront have agreed, via xenstore, to use the feature netback seems to
set the flag every time it would have previously notified netfront.
Ian.
On Thu, 2009-10-01 at 01:22 +0100, Xu, Dongxiao wrote:> Resend and put the patch in attachment.
>
> Patch the Xen version of ring.h
>
> Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
>
> diff -r 8fc927798476 xen/include/public/io/ring.h
> --- a/xen/include/public/io/ring.h Tue Sep 01 11:36:51 2009 +0100
> +++ b/xen/include/public/io/ring.h Thu Oct 01 02:11:45 2009 +0800
> @@ -97,7 +97,8 @@ struct __name##_sring {
> struct __name##_sring { \
> RING_IDX req_prod, req_event; \
> RING_IDX rsp_prod, rsp_event; \
> - uint8_t pad[48]; \
> + uint8_t netfront_smartpoll_active; \
> + uint8_t pad[47]; \
> union __name##_sring_entry ring[1]; /* variable-length */ \
> }; \
> \
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
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Paul Durrant
2009-Oct-01 14:21 UTC
Re: [Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
Xu, Dongxiao wrote:> We found that the event notification frequency is still high in some network cases. NAPI polls only for a little > time slot and does not efficient enough in our backend/frontend case. Actually our patch repeated calling NAPI > interface to do more polling, and netback will NOT notify netfront during this period. Once netfront polling out > all the data, and finds that there is no more data arrive/send during the next 100ms, the timer will stop working > to end the polling. > This filed ''smart_poll_active'' is shared by netfront and netback, to indicate whether netfront is polling data. > So this filed is necessary for netback to notify netfront if this flag is not set. > This field is different from the flag in xenstore, which indicates whether other-end has this new feature. If other-end doesn''t support the new feature, everything goes in the original way. >If you want to prevent event notification, why not simply mask out your port? Paul _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Ian Campbell
2009-Oct-02 09:41 UTC
RE: [Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
On Thu, 2009-10-01 at 15:02 +0100, Xu, Dongxiao wrote:> We found that the event notification frequency is still high in some network cases. NAPI polls only for a little > time slot and does not efficient enough in our backend/frontend case. Actually our patch repeated calling NAPI > interface to do more polling, and netback will NOT notify netfront during this period. Once netfront polling out > all the data, and finds that there is no more data arrive/send during the next 100ms, the timer will stop working > to end the polling.Isn''t that an argument for improving NAPI rather than coding workarounds into each driver? As physical NICs increase in speed it seems like NAPI will need to increase its efficiency in a similar manner. It would be interesting to run the patches past netdev@vger.> This filed ''smart_poll_active'' is shared by netfront and netback, > to indicate whether netfront is polling data. > So this filed is necessary for netback to notify netfront if this flag > is not set.Right, but that doesn''t justify sticking a netfront specific field in a generic ring structure. I can''t help but wonder if there is some better way to communicate this shared state. For instance netback sets the flag every time it notifies the frontend, therefore isn''t receiving an interrupt on the frontend enough to infer that smart polling should be marked as active? Or can this information be encoded into sring->{req,rsp}_event and the smartpoll checks integrated into RING_PUSH_*_AND_CHECK_NOTIFY? At the very least the field should be called {req,rsp}_smartpoll_active to allow other consumers of the generic ring structure to use it if they wish. Ian.> > Thanks! > Dongxiao > > ________________________________________ > From: Ian Campbell [Ian.Campbell@citrix.com] > Sent: Thursday, October 01, 2009 3:03 AM > To: Xu, Dongxiao > Cc: xen-devel@lists.xensource.com; Keir Fraser > Subject: Re: [Xen-devel][PATCH] VNIF: Using smart polling instead of event notification. > > You are adding a netfront specific field to the generic ring structure? > That seems rather ugly. > > Is this even necessary as a piece of shared state? Once netback and > netfront have agreed, via xenstore, to use the feature netback seems to > set the flag every time it would have previously notified netfront. > > Ian. > > On Thu, 2009-10-01 at 01:22 +0100, Xu, Dongxiao wrote: > > Resend and put the patch in attachment. > > > > Patch the Xen version of ring.h > > > > Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com> > > > > diff -r 8fc927798476 xen/include/public/io/ring.h > > --- a/xen/include/public/io/ring.h Tue Sep 01 11:36:51 2009 +0100 > > +++ b/xen/include/public/io/ring.h Thu Oct 01 02:11:45 2009 +0800 > > @@ -97,7 +97,8 @@ struct __name##_sring { > > struct __name##_sring { \ > > RING_IDX req_prod, req_event; \ > > RING_IDX rsp_prod, rsp_event; \ > > - uint8_t pad[48]; \ > > + uint8_t netfront_smartpoll_active; \ > > + uint8_t pad[47]; \ > > union __name##_sring_entry ring[1]; /* variable-length */ \ > > }; \ > > \ > > _______________________________________________ > > 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
Jeremy Fitzhardinge
2009-Oct-02 19:10 UTC
Re: [Xen-devel][PATCH] VNIF: Using smart polling instead of event notification.
On 10/02/09 02:41, Ian Campbell wrote:> On Thu, 2009-10-01 at 15:02 +0100, Xu, Dongxiao wrote: > >> We found that the event notification frequency is still high in some network cases. NAPI polls only for a little >> time slot and does not efficient enough in our backend/frontend case. Actually our patch repeated calling NAPI >> interface to do more polling, and netback will NOT notify netfront during this period. Once netfront polling out >> all the data, and finds that there is no more data arrive/send during the next 100ms, the timer will stop working >> to end the polling. >> > Isn''t that an argument for improving NAPI rather than coding workarounds > into each driver? As physical NICs increase in speed it seems like NAPI > will need to increase its efficiency in a similar manner. > > It would be interesting to run the patches past netdev@vger. >Yes. NAPI is intended to address precisely this issue, so it should be made to work.>> This filed ''smart_poll_active'' is shared by netfront and netback, >> to indicate whether netfront is polling data. >> So this filed is necessary for netback to notify netfront if this flag >> is not set. >> > Right, but that doesn''t justify sticking a netfront specific field in a > generic ring structure. >This kind of poll/interrupt switch isn''t network-specific though; this just happens to be the first user. Presumably other devices with a high rate of small messages could also take advantage of it. J _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
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