Re: More Slowdown - testscript

[Craig Shelley <craig@microtron.org.uk>]

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Hi,

The slow sync problems still exist with fresh vanilla kernel patched
with Reiser4 only (reiser4-for-2.6.14-1.patch). The slow sync occurs
regardless of which IO scheduler is in use.

craig@teratron.lan.etheus.net:~$ uname -a
Linux teratron.lan.etheus.net 2.6.14.2 #2 PREEMPT Tue Nov 22 23:48:39
GMT 2005 i686 GNU/Linux

See the attached testscript.sh 
These are the results from the script:

sync a1

real    0m1.301s
user    0m0.000s
sys     0m0.000s


sync a2

real    0m0.341s
user    0m0.004s
sys     0m0.000s


sync a3

real    0m0.341s
user    0m0.004s
sys     0m0.004s


sync a4

real    0m0.307s
user    0m0.000s
sys     0m0.000s


Performing recursive ls

real    0m0.307s
user    0m0.080s
sys     0m0.220s


sync b1

real    0m9.716s
user    0m0.000s
sys     0m0.024s


sync b2

real    0m0.391s
user    0m0.004s
sys     0m0.000s


sync b3

real    0m0.316s
user    0m0.000s
sys     0m0.000s


sync b4

real    0m0.341s
user    0m0.000s
sys     0m0.000s


Performing recursive ls

real    0m0.734s
user    0m0.216s
sys     0m0.516s


sync c1

real    0m53.698s
user    0m0.000s
sys     0m0.108s


sync c2

real    0m0.665s
user    0m0.000s
sys     0m0.004s


sync c3

real    0m0.125s
user    0m0.000s
sys     0m0.008s


sync c4

real    0m0.125s
user    0m0.000s
sys     0m0.000s




Sync a1->a4 execute relatively quickly
The recursive ls happen very quickly because the data is already cached.
Syncs immediately after the recursive ls take ages. This is really
strange since the recursive ls does not touch the disk because the data
is cached.
My guess is that when sync is called, the cache of ALL recently accessed
data is either being committed back to disk, or being re-read. 

-- 
Craig Shelley
EMail: craig@microtron.org.uk
Jabber: shell@jabber.earth.li

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