[Dovecot] severe performance problem (mail cache related?)

Dan Price dp at eng.sun.com
Fri Feb 16 23:01:47 UTC 2007

On Fri 16 Feb 2007 at 08:24AM, Jeff A. Earickson wrote:
> >There are madvise(MADV_SEQUENTIAL) calls with mmap_disable=no though.
> >
> >
> Dan,
>    Could you give us other Sun users a few details of your setup, so we
> can avoid this hole?  I am running rc22 on a T2000, Solaris 10 11/06
> plus (mostly) current patches, ZFS version 3 for my user homedirs (where
> cache files and folders go), INBOXes NFS mounted from another Sun S10
> box (NFS version 4).  I have never touched any of the mmap related settings
> in dovecot.conf.  The whole thing works beautifully for 3000 users.
> The T2000 never breaks a sweat.  The users are happy.

That's good news!

Well the docs say that mmap_disable=yes is important if you
are using NFS-- in which case, you'll want the patches Timo just
integrated into CVS, if users have large mail cache files, otherwise
you'll hit the performance bug I did.

Timo-- why is mmap_disable so important for NFS?

I have been thinking that dovecot should auto-sense the filesystem
the various files live on, and adapt its behavior-- (for example, in
our environment I've added a "don't bother to fsync on ZFS" patch).
Many environments are mixes of NFS and other FS's, as in Jeff's case,
so being able to auto-sense and customize behavior would probably
be a big win.


Daniel Price - Solaris Kernel Engineering - dp at eng.sun.com - blogs.sun.com/dp

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