linux-kernel - Re: [PATCH v2 0/4] implement vcpu preempted check

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Date:	Wed, 6 Jul 2016 09:47:18 +0200
From:	Juergen Gross <jgross@...e.com>
To:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	virtualization@...ts.linux-foundation.org,
	linux-s390@...r.kernel.org, mingo@...hat.com, mpe@...erman.id.au,
	paulus@...ba.org, benh@...nel.crashing.org,
	paulmck@...ux.vnet.ibm.com, waiman.long@....com,
	will.deacon@....com, boqun.feng@...il.com, dave@...olabs.net,
	schwidefsky@...ibm.com, pbonzini@...hat.com,
	xen-devel-request@...ts.xenproject.org
Subject: Re: [PATCH v2 0/4] implement vcpu preempted check

On 06/07/16 08:52, Peter Zijlstra wrote:
> On Tue, Jun 28, 2016 at 10:43:07AM -0400, Pan Xinhui wrote:
>> change fomr v1:
>> 	a simplier definition of default vcpu_is_preempted
>> 	skip mahcine type check on ppc, and add config. remove dedicated macro.
>> 	add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner. 
>> 	add more comments
>> 	thanks boqun and Peter's suggestion.
>>
>> This patch set aims to fix lock holder preemption issues.
>>
>> test-case:
>> perf record -a perf bench sched messaging -g 400 -p && perf report
>>
>> 18.09%  sched-messaging  [kernel.vmlinux]  [k] osq_lock
>> 12.28%  sched-messaging  [kernel.vmlinux]  [k] rwsem_spin_on_owner
>>  5.27%  sched-messaging  [kernel.vmlinux]  [k] mutex_unlock
>>  3.89%  sched-messaging  [kernel.vmlinux]  [k] wait_consider_task
>>  3.64%  sched-messaging  [kernel.vmlinux]  [k] _raw_write_lock_irq
>>  3.41%  sched-messaging  [kernel.vmlinux]  [k] mutex_spin_on_owner.is
>>  2.49%  sched-messaging  [kernel.vmlinux]  [k] system_call
>>
>> We introduce interface bool vcpu_is_preempted(int cpu) and use it in some spin
>> loops of osq_lock, rwsem_spin_on_owner and mutex_spin_on_owner.
>> These spin_on_onwer variant also cause rcu stall before we apply this patch set
>>
> 
> Paolo, could you help out with an (x86) KVM interface for this?

Xen support of this interface should be rather easy. Could you please
Cc: xen-devel-request@...ts.xenproject.org in the next version?


Juergen