Subject: Re: slow disk access with large cpg values
To: Frederick Bruckman <fredb@immanent.net>
From: Lubos Vrbka <shnek@tiscali.cz>
List: netbsd-users
Date: 04/21/2004 20:52:12
> There are other, more significant changes between 1.6.2 and current,
> particularly in the way files are laid out on the disk. If you assume
> that writing is the bottleneck, your result suggests a huge win for
> the new dirpref code, but there isn't really enough information:
> we'd need to see OLD -> OLD and NEW -> NEW, and perhaps whether newly
> written files can be read back any faster from the old volume than the
> old files that were created under 1.6.2.
just to complete the information - this computer started as 1.6.1 last
autumn and almost immediatelly was turned into -current (for SMP support)
i must apologize for bad information, the situation is just reversed...
i mixed 2 "labels" - from now i'll report it as SMALL (=OLD) and LARGE
(=NEW)
160mb of data (values from my latest tests):
copy LARGE->LARGE 68.70s
move LARGE->LARGE 0.01s
copy SMALL->SMALL 8.25s
move SMALL->SMALL 0.00s
copy SMALL->LARGE 56.10s
move SMALL->LARGE 63.37s
copy LARGE->SMALL 8.42s
move LARGE->SMALL 8.31s
> Are the disks of the same model? Are you using softdeps? If
> not, have you tried using softdeps?
both disks are exactly the same model. there is some difference in
partitioning (LARGE disk is single partition, SMALL is divided in 3
partitions).
if you need any information (dmesg, ...) or if i should do some other
tests, just let me know.
> There's not enough information there to draw a conclusion. Do you mean
> that the command returns quickly, but the operation takes a long time
> to commit to disk? Are operations on the old volume really slower than
> they were under 1.6.2, or are they just slower than operations on new
> volumes?
midnightcommander stuff: when i move file from new volume (LARGE) to the
old one (SMALL), everything is smooth and fast - progress bar just goes
on without stopping (reported average speed is something about
16-18MB/second). when i do it the other way around, there are several
stops during the moving of the file - i.e. progress bar freezes several
times for several seconds and then continues (reported average speed is
about 2-3MB/second). when the indicator hits 99-100% it stops for longer
time.
i haven't tried softdeps, should i? i thought that i'd rather avoid it
since i saw some problems with them were reported on the netbsd-current
maillist, but if it is safe and give me some performance improvement,
why not? :)
i guess i just need to rebuild my kernel with support for these?
regards,
--
Lubos
_@_"