High CPU usage

[Sebastian Spaeth]

On Fri, 9 Dec 2011 12:55:45 +0300, Leonid Evdokimov wrote:
> I gave sqlite backend a try - and it's working much better in terms of
> CPU usage.
> 
> Initial folders scan used 120% of CPU, but further copying is almost
> painless. My laptop is cool again! :)

Great to hear that it helps reduce the CPU usage. OLI was writing way
too much for every single change and sqlite helps greatly with
that. That's why it was implemented.

It was marked as experimental first, and recent releases dropped the
experimental note.
I plan to migrate the default to using the sqlite database in due
time. The performance implications are described in the latest release's
manual in the section Synchronization Performance:

"""The default status cache is a plain text file that will write out the
complete file for each single new message (or even changed flag) to a
temporary file. If you have plenty of files in a folder, this is a few
hundred kilo to megabytes for each mail and is bound to make things
slower. I recommend to use the sqlite backend for that. See the
status_backend = sqlite setting in the example offlineimap.conf. You
will need to have python-sqlite installed in order to use this. This
will save you plenty of disk activity. Do note that the sqlite backend
is still considered experimental as it has only been included recently
(although a loss of your status cache should not be a tragedy as that
file can be rebuild automatically)"""

Sebastian
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