Re: intro

[Sergey Poznyakoff]

> Is MMIO, Memory Map files? if yes we do that for Read-only files.
> But it turns out that the performance gain is relatively small
> for big files(lots of page fault) and most of the time the spool
> is on remote machine access across NFS.

On my server (which is now a bit short of RAM for its 5000 users)
I noticed considerable loss of performance and had to manually disable
mmapping. All pop3d daemons spent most of their time in
noninterruptible sleep on msync(), which is called from
mailbox_is_updated(). The latter is called before processing each
command, so the effect was terrible. That makes me think about
a special option to configure, say --disable-mmap.

Regards,
Sergey