[Dovecot] imap memory footprint rather large

[martin f krafft]

Dear list,

I am experimenting with a new mail handling setup and it involves
a single IMAP folder with just under 70'000 messages. When
OfflineIMAP connects to the server, the imap process starts to eat
up a lot of memory:

  PID   USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  15607 madduck   35  19  283m 244m 239m D 16.9 49.3   0:09.96 imap

On the contrary, when "online" client, such as Thunderbird connect,
memory usage is around 10m, which is entirely acceptable.

The way offlineimap reads may is by FETCHing metadata, then
APPENDing new local mail, SEARCHing for the UIDs of each uploaded
mail, and finally FETCHing new remote mail.

Memory use seems to be O(n) in the size of the folder. On the folder
with 70k messages, dovecot seems to allocate 280m of memory, which
it then fills to about 70% during the metadata FETCH, and then keeps
growing while APPEND/SEARCHing the new local messages.

The 70k mailbox is just short of 600Mb in size on disk. Dovecot uses
280Mb to serve it. Is it possible that dovecot is reading too much
into memory, or over-optimising?

Can I somehow tweak this to lower the memory footprint?

Cheers,

-- 
martin;              (greetings from the heart of the sun.)
  \____ echo mailto: !#^."<*>"|tr "<*> mailto:" net at madduck
 
"the unexamined life is not worth living" 
                                                             -- platon
 
spamtraps: madduck.bogus at madduck.net
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