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List:       kde-pim
Subject:    Re: [Kde-pim] Review Request 117975: Change libmaildir listNew and listCurrent functions to explicet
From:       "Martin Steigerwald" <martin () lichtvoll ! de>
Date:       2014-05-05 12:07:09
Message-ID: 20140505120709.19582.78654 () probe ! kde ! org
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This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/117975/
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(Updated May 5, 2014, 12:07 p.m.)


Status
------

This change has been marked as submitted.


Review request for KDEPIM, KDEPIM-Libraries, Andras Mantia, David Faure, and Sergio \
Luis Martins.


Bugs: 334218
    http://bugs.kde.org/show_bug.cgi?id=334218


Repository: kdepim-runtime


Description
-------

On trying to find the cause for Akonadi maildir resource hogging up a Sandybridge \
core for minutes without any notable MySQL or disk activity, Sergio recommended doing \
a callgrind run. This revealed a bottleneck with QDir.entryList and there \
specifically in QAlgorihmsPrivate::qSortHelper[1].

Calling setSorting(QDir::NoSort) on the QDir object gets rid of the sorting. This I \
did twice in maildir.ccp and twice in keycache.cpp for listCurrent and listNew \
functions there.

It is not yet clear whether this change is safe, but on my tests it appears to do. \
Moving and filtering mails still work okay. I will CC Andras on this as Sergio tried \
to ping him about this change.

I think it is fair to say that this change has a *huge* impact on Akonadi maildir \
performance with large maildir and I recommend to backport this for stable branch as \
well once changing to no sorting is considered to be safe.

Thanks to Sergio and David for pointing out the sorting issue, telling how to change \
to no sorting and general help.

See also:

Bug 334218 - synchronizations of large folders with filesystem contents hogs a \
Sandybridge core for minutes https://bugs.kde.org/334218

[1] https://bugs.kde.org/show_bug.cgi?id=334218#c4

[2] Bug 334206 - While maildir resources synchronizes a folder KMail blocks on \
switching to a different folder: https://bugs.kde.org/334206


Diffs
-----

  resources/maildir/libmaildir/keycache.cpp f0af9c47cef63dac45ae68dd94fa17a040dc1593 
  resources/maildir/libmaildir/maildir.cpp 9bd380201a1a250ecfe354dd99946e8dae0ab668 

Diff: https://git.reviewboard.kde.org/r/117975/diff/


Testing
-------

In my tests with KMail SC 4.12.4 Debian unstable packages and Akonadi and kdepimlibs \
from Git it works well. Well basically Akonadi maildir resource changed from being a \
CPU hog for minutes to hardly every appearing in a 10 second measurement average \
snapshot of atop anymore. KMail hardly blocks on folder changes anymore, which I \
still believe to be a different issue tough[2].

Mail filtering and moving mails to a different folder still works ago. And KMail is \
subjectively much faster. It completely changes my KMail experience from being \
unbearable at times to quite pleasant.


Thanks,

Martin Steigerwald

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