Xen devel - Aug 2006 - RE: [Patch][RFC] Support "xm dump" (is Re: Re: [Patch]Enable "sysrq c" handler for domU coredump)

Two things:

1. I''m not convinced ''xm crash'' is needed -
''xm destroy'' will do this
(and if you want
   a dump, do ''xm dump'' followed by ''xm
destroy'')

2. I don''t see the point of the --noreboot option on ''xm
dump'' -- I
think this command
   should simply live-dump the specified domain - as above you can use
other commands
   to cause the domain to restart afterwards.

3. There''s no need to pause the domain to dump it - I actually wrote a
little utility
   to live dump a guest (based on xenconsoled and attached) and it seems
to work
   quite nicely! This could easily be morphed into the ''xm
dump'' command
- it just
   didn''t occur to me at the time!

Simon

> -----Original Message-----
> From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-
> bounces@lists.xensource.com] On Behalf Of Akio Takebe
> Sent: Thursday, August 03, 2006 8:57 AM
> To: Tristan Gingold; John Levon; Keir Fraser
> Cc: Muli Ben-Yehuda; Horms; Akio Takebe; xen-devel; Kouya Shimura
> Subject: Re: [Patch][RFC] Support "xm dump" (is Re: [Xen-devel]
Re:
> [Patch]Enable "sysrq c" handler for domU coredump)
> 
> Hi, all
> 
> >>   For example panic dump option is used when domU kernel is
hungup,
> >>   and we want to reboot and make coredump atomatically.
> >I''d prefer ''xm crash'' (or ''xm
panic'') and ''xm dump'' .
> >I''d prefer ''xm dump'' *not* to panic by
default.  It is too dangerous.
> >
> OK. I also think both are necessary.
> How about the following specification?
> 
> 1. xm crash
>    This is only for crashing a domain.
>    If enable-dump is yes, we can get the domain''s core after
crash.
>    And If we want to atomatically reboot, we should set
> on_crash=''restart''
>    in domain configuration.
> 
> 2. xm dump
>    This is for live dumping a domain.
>    This implementation is:
>      1. pause the domain
>      2. dumping the domain
>      3. unpause the domain
>      4. reboot (if --noreboot option, don''t reboot)
> 
>      I think we want to reboot when we want to dump.
>      So I want to be default reboot.
> 
>    BTW, I think the feature to online-dump domain and
>    hypervisor is also necessary.(meaning online is "don''t
pause")
> 
> Best Regards,
> 
> Akio Takebe
> 
> 
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> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

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Hi, Simon
>Two things:
>
>1. I''m not convinced ''xm crash'' is needed -
''xm destroy'' will do this
>(and if you want
>   a dump, do ''xm dump'' followed by ''xm
destroy'')
>
What do you mean?
I think we cannot dump with "xm destroy" now.
"xm destory" only call the following domain_kill().
void domain_kill(struct domain *d)
{
    domain_pause(d);

    if ( test_and_set_bit(_DOMF_dying, &d->domain_flags) )
        return;

    gnttab_release_mappings(d);
    domain_relinquish_resources(d);
    put_domain(d);

    send_guest_global_virq(dom0, VIRQ_DOM_EXC);
}

Will anyone add crash option in "xm destory" in the feature?
>2. I don''t see the point of the --noreboot option on ''xm
dump'' -- I
>think this command
>   should simply live-dump the specified domain - as above you can use
>other commands
>   to cause the domain to restart afterwards.
>
Ordinary dump features have atomatically rebooting features.
(e.g. diskdump, kdump, and so on)
So I think this is necessary.
>3. There''s no need to pause the domain to dump it - I actually
wrote a
>little utility
>   to live dump a guest (based on xenconsoled and attached) and it seems
>to work
>   quite nicely! This could easily be morphed into the ''xm
dump'' command
>- it just
>   didn''t occur to me at the time!
>
Your xendump command is dump feature without pause.
In the case without pause, domain''s memory is modified while dumping. 
I think both w/o and w pause are needed.

Best Regards,

Akio Takebe


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On Fri, Aug 04, 2006 at 12:24:27AM +0900, Akio Takebe wrote:
> >   quite nicely! This could easily be morphed into the ''xm
dump'' command
> >- it just
> >   didn''t occur to me at the time!
> >
> Your xendump command is dump feature without pause.
> In the case without pause, domain''s memory is modified while
dumping.
> I think both w/o and w pause are needed.
On the presumption that dumping can take quite a while, I see that not
pausing the domain can be useful. So perhaps:

	xm dump [-Lc] <dom> <filename>

Default: non-destructive, paused dump

-L: live (don''t pause the domain)
-c: crash the domain

It should take a filename to dump to...

regards
john

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Hi, John

Thank you for your comments.
We''re making new patch. 
We''d like to reflect your comments as much as possible.
After post our patch, please review it.
So please wait. :-)

Best Regards,

Akio Takebe
>On Fri, Aug 04, 2006 at 12:24:27AM +0900, Akio Takebe wrote:
>
>> >   quite nicely! This could easily be morphed into the ''xm
dump'' command
>> >- it just
>> >   didn''t occur to me at the time!
>> >
>> Your xendump command is dump feature without pause.
>> In the case without pause, domain''s memory is modified while
dumping.
>> I think both w/o and w pause are needed.
>
>On the presumption that dumping can take quite a while, I see that not
>pausing the domain can be useful. So perhaps:
>
>	xm dump [-Lc] <dom> <filename>
>
>Default: non-destructive, paused dump
>
>-L: live (don''t pause the domain)
>-c: crash the domain
>
>It should take a filename to dump to...
>
>regards
>john

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