fsync() takes about 0.06 second ---makes Cyrus deliver slow

[Daniel Nilsson]

Su Li wrote:
> Daniel,
> 
> My Linux is red hat 7.2-1 with kernel 2.4.7-10. The file system is ext3.
> Hard disk it RAID5. 
> 
> -----
> Besides, I did some calculation on the time of the system calls on a
> new-email. 3 fcync takes about 0.15 seconds. Each mail overall takes 0.65
> seconds. I see the number of locks and deliver process can go up to
> thousands. Maybe some thing else is also taking big time, say the
> communication between deliver and lmtpd? 
> 
> Anyway, I'll keep trying. Thanks for every body's help. If anybody got some
> idea, please let me know.

Su,

The interesting thing here is that you are using ext3. I haven't tried 
ext3 myself but from what I understand using ext3 you get journaling of 
both data and metadata where for example reiserfs only journals 
metadata. This obviously has advantages if you are worried about crashes 
and such, but at the cost of performance.

I would try using a different filesystem, you can try both ext2 and 
reiserfs to see what the performance impacts are and then make a 
tradeoff on which one to use. Do you fell like you need a journaling 
filesystem for this task ?

-- 
Daniel Nilsson
Senior Consultant
Signal Integrity Software Inc.
6 Clock Tower Place, Suite 250
Maynard, MA 01754
Phone: (978) 461-0449, ext 12
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http://www.sisoft.com