linux-kernel - Re: [PATCH] sched: recover sched_yield task running time increase

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Message-ID: <4D9D55EF.3090606@redhat.com>
Date:	Thu, 07 Apr 2011 02:13:03 -0400
From:	Rik van Riel <riel@...hat.com>
To:	"Alex,Shi" <alex.shi@...el.com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"Chen, Tim C" <tim.c.chen@...el.com>,
	"Li, Shaohua" <shaohua.li@...el.com>
Subject: Re: [PATCH] sched: recover sched_yield task running time increase

On 04/06/2011 11:08 PM, Alex,Shi wrote:
> On Wed, 2011-04-06 at 16:04 +0800, Peter Zijlstra wrote:
>> On Wed, 2011-04-06 at 06:33 +0800, Alex Shi wrote:

>> You do know that any app that relies on sched_yield behaviour is more
>> than broken? Using sched_yield() for anything other than SCHED_FIFO
>> tasks is well outside spec.
>>
>> Furthermore, apparently you used sysctl_sched_compat_yield, which was
>> bound to disappear some time, since with the default settings the yield
>> semantics didn't actually change.
>
> Yes, I used sched_compat_yield, otherwise volano will become extremely
> slow in my single machine testing. We may reconsider our testing
> setting.

With what JVM is this happening?

Surely not every JVM uses user space spinlocks and
yield, when we have futexes available?



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