linux-kernel - Re: BFQ speed tests [was Re: [PATCH RFC - TAKE TWO - 00/12] New version of the BFQ I/O Scheduler]

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Date:	Wed, 11 Jun 2014 22:45:06 +0200
From:	Paolo Valente <paolo.valente@...more.it>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Pavel Machek <pavel@....cz>, Tejun Heo <tj@...nel.org>,
	Jens Axboe <axboe@...nel.dk>, Li Zefan <lizefan@...wei.com>,
	Fabio Checconi <fchecconi@...il.com>,
	Arianna Avanzini <avanzini.arianna@...il.com>,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org
Subject: Re: BFQ speed tests [was Re: [PATCH RFC - TAKE TWO - 00/12] New version of the BFQ I/O Scheduler]


Il giorno 04/giu/2014, alle ore 13:59, Takashi Iwai <tiwai@...e.de> ha scritto:

> […]
> I've been using BFQ for a while and noticed also some obvious
> regression in some operations, notably git, too.
> For example, git grep regresses badly.
> 
> I ran "test git grep foo > /dev/null" on linux kernel repos on both
> rotational disk and SSD.
> […]
> 
> BFQ seems behaving bad when reading many small files.
> 

The fix I described in my last reply to Pavel's speed tests
(https://lkml.org/lkml/2014/6/4/94) apparently solves also this problem.
As I wrote in that reply, the new fixed version of bfq is here:
http://algogroup.unimore.it/people/paolo/disk_sched/debugging-patches/3.16.0-rc0-v7rc5.tgz

These are our results, for your test, with this fixed version of bfq.

time git grep foo > /dev/null

Rotational disk:
 CFQ:
   2.86user 4.87system 0:29.51elapsed 26%CPU
   2.87user 4.87system 0:30.30elapsed 25%CPU
   2.82user 4.90system 0:29.13elapsed 26%CPU

 BFQ:
   2.81user 4.97system 0:25.96elapsed 29%CPU
   2.83user 5.02system 0:24.79elapsed 31%CPU
   2.85user 4.95system 0:24.73elapsed 31%CPU

SSD:
 CFQ:
   2.04user 3.93system 0:03.88elapsed 153%CPU
   2.12user 3.85system 0:03.89elapsed 153%CPU
   2.05user 3.92system 0:03.89elapsed 153%CPU

 BFQ:
   2.10user 3.86system 0:03.89elapsed 153%CPU
   2.05user 3.90system 0:03.88elapsed 153%CPU
   2.01user 3.95system 0:03.89elapsed 153%CPU

time git grep foo HEAD > /dev/null

SSD:
 CFQ:
   5.11user 0.38system 0:06.71elapsed 81%CPU
   5.21user 0.36system 0:06.78elapsed 82%CPU
   5.05user 0.41system 0:06.69elapsed 81%CPU

 BFQ:
   5.17user 0.39system 0:06.77elapsed 82%CPU
   5.13user 0.37system 0:06.73elapsed 81%CPU
   5.17user 0.37system 0:06.78elapsed 81%CPU

Should you be willing to provide further feedback on this and other tests,
we would of course really appreciate it.

Thanks again for your report,
Paolo--
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