linux-kernel - Re: [PATCH] sched/rt: overrun could happen in start_hrtick

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Message-ID: <53BB5A13.1070305@huawei.com>
Date:	Tue, 8 Jul 2014 10:40:19 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	"xiaofeng.yan" <xiaofeng.yan@...wei.com>
CC:	Peter Zijlstra <peterz@...radead.org>, <mingo@...hat.com>,
	<linux-kernel@...r.kernel.org>, <xiaofeng.yan2012@...il.com>,
	Juri Lelli <juri.lelli@...il.com>
Subject: Re: [PATCH] sched/rt: overrun could happen in start_hrtick_dl

On 2014/7/8 9:10, xiaofeng.yan wrote:
> On 2014/7/7 16:41, Peter Zijlstra wrote:
>> On Fri, Jul 04, 2014 at 12:02:21PM +0000, xiaofeng.yan wrote:
>>> It could be wrong for the precision of runtime and deadline
>>> when the precision is within microsecond level. For example:
>>> Task runtime deadline period
>>>   P1   200us   500us   500us
>>>
>>> This case need enbale HRTICK feature by the next command
>>> PC#echo "HRTICK" > /sys/kernel/debug/sched_features
>>> PC#./schedtool -E -t 200000:500000 -e ./test&
>>> PC#trace-cmd record -e sched_switch
>> Are you actually using HRTICK ?
> yes, If HRTICK is close , then all of runtime and deadline will be wrong.

I think what peter meant is, do you use HRTICK in products or
just use it for testing/experiment?

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