From: Ingo Molnar <mingo@elte.hu>
To: Avi Kivity <avi@redhat.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mark Langsdorf <mark.langsdorf@amd.com>,
Joerg Roedel <joerg.roedel@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][KVM][retry 1] Add support for Pause Filtering to AMD SVM
Date: Mon, 11 May 2009 16:15:03 +0200 [thread overview]
Message-ID: <20090511141503.GC6175@elte.hu> (raw)
In-Reply-To: <4A02FECC.6060609@redhat.com>
* Avi Kivity <avi@redhat.com> wrote:
>> +static int pause_interception(struct vcpu_svm *svm, struct kvm_run
>> *kvm_run)
>> +{
>> + /* Simple yield */
>> + vcpu_put(&svm->vcpu);
>> + schedule();
>> + vcpu_load(&svm->vcpu);
>> + return 1;
>> +
>
> Ingo, will this do anything under CFS, or will CFS note that
> nothing has changed in the accounting and reschedule us
> immediately?
The scheduler will yield to another task only if the current task
has become ineligible. I.e schedule() is largely a NOP on
TASK_RUNNING tasks (i.e. here).
I.e. this is a somewhat poor solution as far as scheduling goes. But
i'm wondering what the CPU side does. Can REP-NOP really take
thousands of cycles? If yes, under what circumstances?
Ingo
WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@elte.hu>
To: Avi Kivity <avi@redhat.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mark Langsdorf <mark.langsdorf@amd.com>,
Joerg Roedel <joerg.roedel@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][retry 1] Add support for Pause Filtering to AMD SVM
Date: Mon, 11 May 2009 16:15:03 +0200 [thread overview]
Message-ID: <20090511141503.GC6175@elte.hu> (raw)
In-Reply-To: <4A02FECC.6060609@redhat.com>
* Avi Kivity <avi@redhat.com> wrote:
>> +static int pause_interception(struct vcpu_svm *svm, struct kvm_run
>> *kvm_run)
>> +{
>> + /* Simple yield */
>> + vcpu_put(&svm->vcpu);
>> + schedule();
>> + vcpu_load(&svm->vcpu);
>> + return 1;
>> +
>
> Ingo, will this do anything under CFS, or will CFS note that
> nothing has changed in the accounting and reschedule us
> immediately?
The scheduler will yield to another task only if the current task
has become ineligible. I.e schedule() is largely a NOP on
TASK_RUNNING tasks (i.e. here).
I.e. this is a somewhat poor solution as far as scheduling goes. But
i'm wondering what the CPU side does. Can REP-NOP really take
thousands of cycles? If yes, under what circumstances?
Ingo
next prev parent reply other threads:[~2009-05-11 14:15 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-05 14:09 [PATCH][KVM] Add support for Pause Filtering to AMD SVM Mark Langsdorf
2009-05-05 16:05 ` Bert Wesarg
2009-05-07 13:55 ` Joerg Roedel
2009-05-07 15:00 ` [PATCH][KVM][retry 1] " Mark Langsdorf
2009-05-07 15:00 ` [PATCH][retry " Mark Langsdorf
2009-05-07 15:31 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 14:15 ` Ingo Molnar [this message]
2009-05-11 14:15 ` [PATCH][retry " Ingo Molnar
2009-05-11 14:24 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 14:24 ` [PATCH][retry " Avi Kivity
2009-05-11 14:33 ` [PATCH][KVM][retry " Ingo Molnar
2009-05-11 14:33 ` [PATCH][retry " Ingo Molnar
2009-05-11 14:51 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 14:51 ` [PATCH][retry " Avi Kivity
2009-05-11 14:59 ` [PATCH][KVM][retry " Ingo Molnar
2009-05-11 14:59 ` [PATCH][retry " Ingo Molnar
2009-05-11 15:12 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 15:12 ` [PATCH][retry " Avi Kivity
2009-05-11 15:18 ` [PATCH][KVM][retry " Ingo Molnar
2009-05-11 15:18 ` [PATCH][retry " Ingo Molnar
2009-05-11 15:28 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 15:28 ` [PATCH][retry " Avi Kivity
2009-05-11 15:36 ` [PATCH][KVM][retry " Langsdorf, Mark
2009-05-11 15:36 ` [PATCH][retry " Langsdorf, Mark
2009-05-11 15:40 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 15:58 ` [PATCH][KVM][retry 1] Add support for Pause Filtering to AMDSVM Langsdorf, Mark
2009-05-11 15:58 ` [PATCH][retry " Langsdorf, Mark
2009-05-11 15:01 ` [PATCH][KVM][retry 1] Add support for Pause Filtering to AMD SVM Peter Zijlstra
2009-05-11 15:01 ` [PATCH][retry " Peter Zijlstra
2009-05-11 15:06 ` [PATCH][KVM][retry " Avi Kivity
2009-05-11 15:06 ` [PATCH][retry " Avi Kivity
2009-05-11 14:42 ` [PATCH][KVM][retry " Peter Zijlstra
2009-05-11 15:05 ` Avi Kivity
2009-05-11 15:05 ` [PATCH][retry " Avi Kivity
2009-05-08 17:03 ` [PATCH][KVM][retry 2] " Mark Langsdorf
2009-05-08 17:03 ` [PATCH][retry " Mark Langsdorf
2009-05-08 18:44 ` [PATCH][KVM][retry " Avi Kivity
2009-05-08 18:44 ` [PATCH][retry " Avi Kivity
2009-05-08 18:47 ` [PATCH][KVM][retry " Langsdorf, Mark
2009-05-08 18:47 ` [PATCH][retry " Langsdorf, Mark
2009-05-19 18:56 ` [PATCH][KVM][retry 3] " Mark Langsdorf
2009-05-19 18:56 ` [PATCH][retry " Mark Langsdorf
2009-05-20 7:40 ` [PATCH][KVM][retry " Ingo Molnar
2009-05-20 7:59 ` Peter Zijlstra
2009-05-20 7:59 ` [PATCH][retry " Peter Zijlstra
2009-05-20 8:38 ` [PATCH][KVM][retry " Avi Kivity
2009-05-20 8:38 ` [PATCH][retry " Avi Kivity
2009-05-20 8:42 ` [PATCH][KVM][retry " Peter Zijlstra
2009-05-20 8:42 ` [PATCH][retry " Peter Zijlstra
2009-05-20 8:49 ` [PATCH][KVM][retry " Avi Kivity
2009-05-20 8:49 ` [PATCH][retry " Avi Kivity
2009-05-20 8:54 ` [PATCH][KVM][retry " Peter Zijlstra
2009-05-20 8:54 ` [PATCH][retry " Peter Zijlstra
2009-05-20 9:04 ` [PATCH][KVM][retry " Avi Kivity
2009-05-20 9:04 ` [PATCH][retry " Avi Kivity
2009-05-20 9:10 ` [PATCH][KVM][retry " Peter Zijlstra
2009-05-20 9:10 ` [PATCH][retry " Peter Zijlstra
2009-05-20 9:17 ` [PATCH][KVM][retry " Avi Kivity
2009-05-20 9:17 ` [PATCH][retry " Avi Kivity
2009-05-20 13:52 ` [PATCH][KVM][retry " Langsdorf, Mark
2009-05-20 13:52 ` [PATCH][retry " Langsdorf, Mark
2009-05-20 12:00 ` [PATCH][KVM][retry " Avi Kivity
2009-05-20 12:00 ` [PATCH][retry " Avi Kivity
2009-05-20 22:25 ` [PATCH][KVM][retry 4] " Mark Langsdorf
2009-05-20 22:25 ` [PATCH][retry " Mark Langsdorf
2009-05-21 8:47 ` [PATCH][KVM][retry " Avi Kivity
2009-05-21 8:47 ` [PATCH][retry " Avi Kivity
2009-07-08 5:19 ` [PATCH][KVM][retry " Sheng Yang
2009-07-08 5:19 ` [PATCH][retry " Sheng Yang
2009-07-08 14:59 ` [PATCH][KVM][retry " Langsdorf, Mark
2009-07-08 14:59 ` [PATCH][retry " Langsdorf, Mark
2009-07-09 1:50 ` [PATCH][KVM][retry " Sheng Yang
2009-07-09 1:50 ` [PATCH][retry " Sheng Yang
2009-07-22 22:40 ` [PATCH][KVM][retry " Langsdorf, Mark
2009-07-22 22:40 ` [PATCH][retry " Langsdorf, Mark
2009-08-05 9:08 ` [PATCH][KVM][retry " Zhai, Edwin
2009-08-05 9:08 ` [PATCH][retry " Zhai, Edwin
2009-05-11 14:38 ` [PATCH][KVM] " Peter Zijlstra
2009-05-11 14:51 ` Ingo Molnar
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