[Dovecot] imap memory footprint rather large

[Timo Sirainen]

On Tue, 2007-08-14 at 08:13 +0200, martin f krafft wrote:
> also sprach Timo Sirainen <tss at iki.fi> [2007.08.14.0028 +0200]:
> > What exactly do you mean by FETCHing metadata? Something like ENVELOPE
> > or BODYSTRUCTURE? And this is fetched for all messages instead of just
> > new ones? That could easily explain why cache is so large.
> 
> The code is:
> 
>   response = imapobj.fetch('1:%d' % maxmsgid, '(FLAGS UID INTERNALDATE)')[1]
> 
> meaning that it obtains (FLAGS UID INTERNALDATE) for all messages in
> a folder every time.

FLAGS and UID are stored in dovecot.index file, and caching only
INTERNALDATE would take maybe 16 bytes/message.

So I guess most of the data in your dovecot.index.cache file came from
some initial FETCH ENVELOPE/BODYSTRUCTURE/etc. for all messages. If you
delete it, it won't probably get as large anymore.

I'm not sure if there's anything I can do on Dovecot's side to make this
work better. This shouldn't be a problem except for large mailboxes that
are accessed with Dovecot for the first time. There the possibilities
are to cache wanted data immediately so that it can be accessed fast the
next time, or not cache it at all the first time and if it's needed
again doing the whole thing all over again.

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