linux-kernel - Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice

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Date:	Tue, 25 Nov 2014 12:23:10 -0700
From:	Khalid Aziz <khalid.aziz@...cle.com>
To:	Davidlohr Bueso <dave@...olabs.net>
CC:	Thomas Gleixner <tglx@...utronix.de>, corbet@....net,
	mingo@...hat.com, hpa@...or.com, peterz@...radead.org,
	riel@...hat.com, akpm@...ux-foundation.org, rientjes@...gle.com,
	ak@...ux.intel.com, mgorman@...e.de, raistlin@...ux.it,
	kirill.shutemov@...ux.intel.com, atomlin@...hat.com,
	avagin@...nvz.org, gorcunov@...nvz.org, serge.hallyn@...onical.com,
	athorlton@....com, oleg@...hat.com, vdavydov@...allels.com,
	daeseok.youn@...il.com, keescook@...omium.org,
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	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice

On 11/25/2014 11:27 AM, Davidlohr Bueso wrote:
> On Tue, 2014-11-25 at 07:45 -0700, Khalid Aziz wrote:
>> This solution has been used by both database and java on other OSs and
>> has shown performance improvement. Andrew had asked for performance
>> numbers on Linux with this patch last time I sent this out and it took
>> me a while to get performance folks to run a full TPC-C workload. They
>> did see a 3% improvement in tpcc as I noted in commit log and that is a
>> significant improvement.
>
> 3% for such a change seems pretty worthless... I would have expected
> this having to impact performance much more.
>

Performance impact will depend upon how big a bottleneck the spinlock 
was creating and how severe the resulting convoy problem was. Database 
guys try to squeeze every bit out of the system and 3% is considered to 
be very good gain. 10% gain would have been nicer :)

--
Khalid
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