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

[Su Li]

Thanks Daniel,

I think performance is the bigger issue for me. I need to get 8-10 messages
per second and right now I only got 1.2-1.5 messages per second. I will
definitely give a try. In the mean time I also looking into my configure to
see if I can get any better there.

I have posted my configure before. I choose db3_nosync to be my
duplicate.db. Can you help me to see, if I can improve performance there? I
post again here. Sorry for that.

./configure --with-auth=unix --without-krb4 --without-ucdsnmp
--with-bdb-incdir=/usr/local/BerkeleyDB.4.0/include
--with-bdb-libdir=/usr/local/BerkeleyDB.4.0/lib --with-dblib=berkeley
--with-dbpath=/usr/local/BerkeleyDB.4.0 --with-lock=fcntl
--with-mboxlist-db=skiplist --with-seen-db=skiplist
--with-duplicate-db=db3_nosync --without-notify --disable-sieve
--enable-fulldirhash --with-idle=no

Thanks a lot.


Su



-----Original Message-----
From: Daniel Nilsson [mailto:dnilsson at sisoft.com]
Sent: September 10, 2002 11:13 AM
To: Su Li
Cc: info-cyrus at lists.andrew.cmu.edu
Subject: Re: fsync() takes about 0.06 second ---makes Cyrus deliver slow


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
Cell:  (508) 783-1379
http://www.sisoft.com