Following this email are the results of a number of tests of various I/O
schedulers:
- 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.
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This archive was generated by hypermail 2b29 : Sun Feb 23 2003 - 22:00:32 EST