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

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Date:	Tue, 8 Jul 2014 10:51:02 +0800
From:	"xiaofeng.yan" <xiaofeng.yan@...wei.com>
To:	Li Zefan <lizefan@...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 10:40, Li Zefan wrote:
> 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?
>
Thanks for your timely comments. In fact, We use HRTICK feature in 
product. We need microsecond level
precision.

Thanks
Yan
> .
>


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