No need to try migration in current context since self migrate
will be handled by next vcpu after context switch.
Signed-off-by Kevin Tian <kevin.tian@intel.com>
diff -r e66f047bc97e xen/common/schedule.c
--- a/xen/common/schedule.c Tue Jan 09 18:56:44 2007 -0800
+++ b/xen/common/schedule.c Thu Jan 11 16:31:37 2007 +0800
@@ -243,7 +243,7 @@ int vcpu_set_affinity(struct vcpu *v, cp
vcpu_schedule_unlock_irqrestore(v, flags);
- if ( test_bit(_VCPUF_migrating, &v->vcpu_flags) )
+ if ( (v != current) && test_bit(_VCPUF_migrating,
&v->vcpu_flags) )
{
vcpu_sleep_nosync(v);
vcpu_migrate(v);
Thanks,
Kevin
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Keir Fraser
2007-Jan-11 09:43 UTC
Re: [Xen-devel] [PATCH] trivial fix for vcpu_set_affinity
It''s true that the vcpu_migrate() is a no-op if v==current, but the vcpu_sleep_nosync() does have to be executed, otherwise current will not be migrated before returning to guest context (because the schedule softirq will not be asserted). This would mean that a dom0 vcpu could no longer synchronously migrate itself. In any case this patch has no upside -- the existing code works just fine. -- Keir On 11/1/07 08:42, "Tian, Kevin" <kevin.tian@intel.com> wrote:> No need to try migration in current context since self migrate > will be handled by next vcpu after context switch. > > Signed-off-by Kevin Tian <kevin.tian@intel.com> > > diff -r e66f047bc97e xen/common/schedule.c > --- a/xen/common/schedule.c Tue Jan 09 18:56:44 2007 -0800 > +++ b/xen/common/schedule.c Thu Jan 11 16:31:37 2007 +0800 > @@ -243,7 +243,7 @@ int vcpu_set_affinity(struct vcpu *v, cp > > vcpu_schedule_unlock_irqrestore(v, flags); > > - if ( test_bit(_VCPUF_migrating, &v->vcpu_flags) ) > + if ( (v != current) && test_bit(_VCPUF_migrating, &v->vcpu_flags) ) > { > vcpu_sleep_nosync(v); > vcpu_migrate(v); > > Thanks, > Kevin > _______________________________________________ > 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
Emmanuel Ackaouy
2007-Jan-11 09:49 UTC
Re: [Xen-devel] [PATCH] trivial fix for vcpu_set_affinity
I don''t get it. If you don''t at least call vcpu_sleep_nosync() on the current context when it changes affinity, how do you initiate a reschedule event? What''s wrong with the code as is? On Jan 11, 2007, at 9:42, Tian, Kevin wrote:> No need to try migration in current context since self migrate > will be handled by next vcpu after context switch. > > Signed-off-by Kevin Tian <kevin.tian@intel.com> > > diff -r e66f047bc97e xen/common/schedule.c > --- a/xen/common/schedule.c Tue Jan 09 18:56:44 2007 -0800 > +++ b/xen/common/schedule.c Thu Jan 11 16:31:37 2007 +0800 > @@ -243,7 +243,7 @@ int vcpu_set_affinity(struct vcpu *v, cp > > vcpu_schedule_unlock_irqrestore(v, flags); > > - if ( test_bit(_VCPUF_migrating, &v->vcpu_flags) ) > + if ( (v != current) && test_bit(_VCPUF_migrating, &v->vcpu_flags) > ) > { > vcpu_sleep_nosync(v); > vcpu_migrate(v); > > Thanks, > Kevin > <set_affinity.patch>_______________________________________________ > 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
Tian, Kevin
2007-Jan-11 09:53 UTC
RE: [Xen-devel] [PATCH] trivial fix for vcpu_set_affinity
Yes, you''re right. Though I test this patch working, it may be instead migrated at later schedule point instead of immediately by this hypercall. Thanks, Kevin>-----Original Message----- >From: Keir Fraser [mailto:keir@xensource.com] >Sent: 2007年1月11日 17:44 >To: Tian, Kevin; xen-devel@lists.xensource.com >Subject: Re: [Xen-devel] [PATCH] trivial fix for vcpu_set_affinity > >It''s true that the vcpu_migrate() is a no-op if v==current, but the >vcpu_sleep_nosync() does have to be executed, otherwise current will >not be >migrated before returning to guest context (because the schedule softirq >will not be asserted). This would mean that a dom0 vcpu could no longer >synchronously migrate itself. In any case this patch has no upside -- the >existing code works just fine. > > -- Keir > >On 11/1/07 08:42, "Tian, Kevin" <kevin.tian@intel.com> wrote: > >> No need to try migration in current context since self migrate >> will be handled by next vcpu after context switch. >> >> Signed-off-by Kevin Tian <kevin.tian@intel.com> >> >> diff -r e66f047bc97e xen/common/schedule.c >> --- a/xen/common/schedule.c Tue Jan 09 18:56:44 2007 -0800 >> +++ b/xen/common/schedule.c Thu Jan 11 16:31:37 2007 +0800 >> @@ -243,7 +243,7 @@ int vcpu_set_affinity(struct vcpu *v, cp >> >> vcpu_schedule_unlock_irqrestore(v, flags); >> >> - if ( test_bit(_VCPUF_migrating, &v->vcpu_flags) ) >> + if ( (v != current) && test_bit(_VCPUF_migrating, >&v->vcpu_flags) ) >> { >> vcpu_sleep_nosync(v); >> vcpu_migrate(v); >> >> Thanks, >> Kevin >> _______________________________________________ >> 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
Tian, Kevin
2007-Jan-11 09:57 UTC
RE: [Xen-devel] [PATCH] trivial fix for vcpu_set_affinity
Yes, I forgot about the reschedule event here, and thus migration is scheduled in other schedule points triggered later. Please forget this patch. :-) Thanks Kevin>-----Original Message----- >From: Emmanuel Ackaouy [mailto:ack@xensource.com] >Sent: 2007年1月11日 17:49 >To: Tian, Kevin >Cc: xen-devel@lists.xensource.com >Subject: Re: [Xen-devel] [PATCH] trivial fix for vcpu_set_affinity > >I don''t get it. > >If you don''t at least call vcpu_sleep_nosync() on the current context >when it changes affinity, how do you initiate a reschedule event? > >What''s wrong with the code as is? > >On Jan 11, 2007, at 9:42, Tian, Kevin wrote: > >> No need to try migration in current context since self migrate >> will be handled by next vcpu after context switch. >> >> Signed-off-by Kevin Tian <kevin.tian@intel.com> >> >> diff -r e66f047bc97e xen/common/schedule.c >> --- a/xen/common/schedule.c Tue Jan 09 18:56:44 2007 -0800 >> +++ b/xen/common/schedule.c Thu Jan 11 16:31:37 2007 +0800 >> @@ -243,7 +243,7 @@ int vcpu_set_affinity(struct vcpu *v, cp >> >> vcpu_schedule_unlock_irqrestore(v, flags); >> >> - if ( test_bit(_VCPUF_migrating, &v->vcpu_flags) ) >> + if ( (v != current) && test_bit(_VCPUF_migrating, >&v->vcpu_flags) >> ) >> { >> vcpu_sleep_nosync(v); >> vcpu_migrate(v); >> >> Thanks, >> Kevin >> ><set_affinity.patch>__________________________________________ >_____ >> 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