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Message-ID: <20160706065255.GH30909@twins.programming.kicks-ass.net>
Date: Wed, 6 Jul 2016 08:52:55 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Cc: 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
Subject: Re: [PATCH v2 0/4] implement vcpu preempted check
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?
Waiman, could you see if you can utilize this to get rid of the
SPIN_THRESHOLD in qspinlock_paravirt?
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