[lkml]   [2003]   [Feb]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectIO scheduler benchmarking

Following this email are the results of a number of tests of various I/O

- Anticipatory Scheduler (AS) (from 2.5.61-mm1 approx)

- CFQ (as in 2.5.61-mm1)

- 2.5.61+hacks (Basically 2.5.61 plus everything before the anticipatory
scheduler - tweaks which fix the writes-starve-reads problem via a
scheduling storm)

- 2.4.21-pre4

All these tests are simple things from the command line.

I stayed away from the standard benchmarks because they do not really touch
on areas where the Linux I/O scheduler has traditionally been bad. (If they
did, perhaps it wouldn't have been so bad..)

Plus all the I/O schedulers perform similarly with the usual benchmarks.
With the exception of some tiobench phases, where AS does very well.

Executive summary: the anticipatory scheduler is wiping the others off the
map, and 2.4 is a disaster.

I really have not sought to make the AS look good - I mainly concentrated on
things which we have traditonally been bad at. If anyone wants to suggest
other tests, please let me know.

The known regressions from the anticipatory scheduler are:

1) 15% (ish) slowdown in David Mansfield's database run. This appeared to
go away in later versions of the scheduler.

2) 5% dropoff in single-threaded qsbench swapstorms

3) 30% dropoff in write bandwidth when there is a streaming read (this is
actually good).

The test machine is a fast P4-HT with 256MB of memory. Testing was against a
single fast IDE disk, using ext2.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:33    [W:0.085 / U:0.532 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site