faster delivery of cyrus imap -- writev() takes 1.2 sec!

[David Lang]

when installing cyrus the instructions tell you to do a chmod +S on some
files and directories.

that tells the system to always access those in sync mode.

try undoing this  (chmod -S) and see how it affects performance. after you
do that then you can evaluate the risk of leaving it off vs the
performance gain.

David Lang


On Sun, 8 Sep 2002, Su Li wrote:

> Date: Sun, 8 Sep 2002 10:54:20 -0400
> From: Su Li <sli at rim.net>
> To: info-cyrus at andrew.cmu.edu
> Subject: RE: faster delivery of cyrus imap -- writev() takes 1.2 sec!
>
> If I send this message the second time. Please igore it.
>
> Can you be more specific which directory Cyrus uses to sync? Does it have
> some thing to do with duplicate delivery mode?
>
>
> Thanks a lot,
>
>
> Su
>
>
> -----Original Message-----
> From: David Lang [mailto:dlang at diginsite.com]
> Sent: September 8, 2002 12:11 AM
> To: Su Li
> Cc: info-cyrus at andrew.cmu.edu
> Subject: Re: faster delivery of cyrus imap -- writev() takes 1.2 sec!
>
>
> did you change the directories that cyrus uses to be synced for every
> write? while that provides extra crash protection is slows things down a
> LOT.
>
> David Lang
>
>  On Sat, 7 Sep 2002, Su Li wrote:
>
> > Date: Sat, 7 Sep 2002 23:23:20 -0400
> > From: Su Li <sli at rim.net>
> > To: info-cyrus at andrew.cmu.edu
> > Subject: faster delivery of cyrus imap -- writev() takes 1.2 sec!
> >
> > Hi,
> >
> > I tried to make Cyrus imap deliver mail faster, by changing
> > --with-duplicated-db to skiplist and disabled notification. It didn't
> work.
> > I am sending email from my testing tool. I run 4 of them, each trying to
> > send one email to mail server with a delay of 20 msec. It seems the Cyrus
> > imap can only process 1 email per second.
> >
> > My configuration for imap is:
> >
> > ./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  --without-notify
> > --disable-sieve --enable-fulldirhash --with-idle=no
> > --with-duplicate-db=skiplist
> >
> > I run "strace -T -p pid", in which pid is pid of lmtpd. The following line
> > catches my eyes.
> >
> > writev(11, [{"\0\0\0018(\"Sat, 7 Sep 2002 22:12:14 -"..., 316},
> > {"\0\0\0Q(\"TEXT\" \"PLAIN\" (\"CHARSET\" {"..., 88}, {"\0\0\0E(\"TEXT\"
> > \"PLAIN\" (\"CHARSET\" {"..., 76},
> > {"\0\0\0000\0\0\0\2\0\0\0\0\0\0\2Y\0\0\2Y\0\0\0000\377\377"..., 52},
> > {"\0\0\0\0", 4}, {"\0\0\0*loadtest <loadtest1586 at web9."..., 48},
> > {"\0\0\0!<loadtest1586 at web9.swlab.rim"..., 40}, {"\0\0\0\0", 4},
> > {"\0\0\0\0", 4}, {"\0\0\0\3NIL\0", 8}], 10) = 640 <1.207524>
> >
> > It takes 1.2 sec to do writev() for each email! I search through the code
> in
> > /imap/messages.c. It looks like the following function is doing the
> writing:
> >
> > /*
> >  * Write the BODY (if 'newformat' is zero) or BODYSTRUCTURE
> >  * (if 'newformat' is nonzero) for 'body' to 'ibuf'.
> >  */
> > static void
> > message_write_body(ibuf, body, newformat)
> >
> > I wonder why writev() takes so long to do the writing? In the mean time I
> > don't found error messages about locking. I guess it is not
> > "duplicate_check" who is take so long. It there any thing to don with my
> > configurations, or sendmail's configuration?
> >
> > Thanks a lot.
> >
> >
> > Su
> >
> > Research In Motion
> > (519)888-7465 ext 3041
>