From: Wanpeng Li <kernellwp@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>,
linux-s390 <linux-s390@vger.kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
mpe@ellerman.id.au, boqun.feng@gmail.com, will.deacon@arm.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Waiman Long <waiman.long@hpe.com>,
virtualization@lists.linux-foundation.org,
Ingo Molnar <mingo@redhat.com>, Paul Mackerras <paulus@samba.org>,
benh@kernel.crashing.org, schwidefsky@de.ibm.com,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, kvm <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 0/4] implement vcpu preempted check
Date: Wed, 6 Jul 2016 21:03:01 +0800 [thread overview]
Message-ID: <CANRm+Cyu0T=gWbZQT5WzdknYQWspRmC2wTt6_KLS4tP9QVuWUA@mail.gmail.com> (raw)
In-Reply-To: <8e8edf1b-b64b-3c44-b580-b9271663844c@redhat.com>
2016-07-06 20:28 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 06/07/2016 14:08, Wanpeng Li wrote:
>> 2016-07-06 18:44 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>>>
>>>
>>> On 06/07/2016 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?
>>>
>>> If it's just for spin loops, you can check if the version field in the
>>> steal time structure has changed.
>>
>> Steal time will not be updated until ahead of next vmentry except
>> wrmsr MSR_KVM_STEAL_TIME. So it can't represent it is preempted
>> currently, right?
>
> Hmm, you're right. We can use bit 0 of struct kvm_steal_time's flags to
> indicate that pad[0] is a "VCPU preempted" field; if pad[0] is 1, the
> VCPU has been scheduled out since the last time the guest reset the bit.
> The guest can use an xchg to test-and-clear it. The bit can be
> accessed at any time, independent of the version field.
I will try to implement it tomorrow, thanks for your proposal. :)
Regards,
Wanpeng Li
next prev parent reply other threads:[~2016-07-06 13:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-28 14:43 [PATCH v2 0/4] implement vcpu preempted check Pan Xinhui
2016-06-28 14:43 ` [PATCH v2 1/4] kernel/sched: introduce vcpu preempted check interface Pan Xinhui
2016-06-28 14:43 ` [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Pan Xinhui
2016-07-05 9:57 ` Wanpeng Li
2016-07-06 4:58 ` xinhui
2016-07-06 6:46 ` Wanpeng Li
2016-07-06 7:58 ` Peter Zijlstra
2016-07-06 8:32 ` Wanpeng Li
2016-07-06 10:18 ` xinhui
2016-07-06 10:54 ` Balbir Singh
2016-07-15 15:35 ` Pan Xinhui
2016-06-28 14:43 ` [PATCH v2 3/4] locking/osq: Drop the overload of osq_lock() Pan Xinhui
2016-06-28 14:43 ` [PATCH v2 4/4] kernel/locking: Drop the overload of {mutex, rwsem}_spin_on_owner Pan Xinhui
2016-07-06 6:52 ` [PATCH v2 0/4] implement vcpu preempted check Peter Zijlstra
2016-07-06 7:47 ` Juergen Gross
2016-07-06 8:19 ` Peter Zijlstra
2016-07-06 8:38 ` Juergen Gross
2016-07-06 12:44 ` Paolo Bonzini
2016-07-06 16:56 ` Christian Borntraeger
2016-07-06 10:05 ` xinhui
2016-07-06 10:44 ` Paolo Bonzini
2016-07-06 11:59 ` Peter Zijlstra
2016-07-06 12:08 ` Wanpeng Li
2016-07-06 12:28 ` Paolo Bonzini
2016-07-06 13:03 ` Wanpeng Li [this message]
2016-07-07 8:48 ` Wanpeng Li
2016-07-07 9:42 ` Peter Zijlstra
2016-07-07 10:12 ` Wanpeng Li
2016-07-07 10:27 ` Wanpeng Li
2016-07-07 11:15 ` Peter Zijlstra
2016-07-07 11:08 ` Peter Zijlstra
2016-07-07 11:09 ` Peter Zijlstra
2016-07-07 11:21 ` Peter Zijlstra
2016-07-11 15:10 ` Waiman Long
2016-07-12 4:16 ` Juergen Gross
2016-07-12 18:16 ` Waiman Long
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