linux-kernel - Re: [PATCH] time,virt: resync steal time when guest & host lose sync

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Message-ID: <CANRm+Cye=ipm5XwhBV-AxjCMZRQTb3ahuYEa6KXBMe_HzxPa2Q@mail.gmail.com>
Date:	Thu, 11 Aug 2016 18:11:32 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Wanpeng Li <wanpeng.li@...mail.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Radim Krcmar <rkrcmar@...hat.com>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH] time,virt: resync steal time when guest & host lose sync

2016-08-11 0:52 GMT+08:00 Rik van Riel <riel@...hat.com>:
> On Wed, 10 Aug 2016 07:39:08 +0800
> Wanpeng Li <kernellwp@...il.com> wrote:
>
>> The regression is caused by your commit "sched,time: Count actually
>> elapsed irq & softirq time".
>
> Wanpeng, does this patch fix your issue?

I test this against kvm guest (nohz_full, four vCPUs running on one
pCPU, four cpuhog processes running on four vCPUs).
before this fix patch:
vCPU0's st is 100%, other vCPUs' st are ~75%.
after this fix patch:
all vCPUs' st are ~85%.
However, w/o commit "sched,time: Count actually elapsed irq & softirq
time", all vCPUs' st are ~75%.

Regards,
Wanpeng Li