Il giorno 04/giu/2014, alle ore 13:59, Takashi Iwai [off-list ref] 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