Review Request 117975: Change libmaildir listNew and listCurrent functions to explicetely not sort QDir.entryList

[Martin Steigerwald]

> On May 5, 2014, 3:08 p.m., Sergio Luis Martins wrote:
> > Commit to stable too ?
> 
> Laurent Montel wrote:
>     Please wait after 4.13.1 it will tag the 8 may.
>     Apply it in 4.13.2 if safe
>     thanks
> 
> Martin Steigerwald wrote:
>     Okay, will wait. I think its good if someone else than me actually also tests it. For me it works really nicely.
> 
> Martin Steigerwald wrote:
>     Hi! So did anyone test with it? It works very well for me. I see higher I/O throughput on accessing folders, but I think thats just due to the fact that there is way less CPU overhead now. It will stat() mail files in random order instead of alphabetically now, I think. Depending on the filesystem implementation and the order in which those files will be created, this may make a difference – accessing in inode number order may help on some filesystems. In any case, subjectively I think it is way better than before. What do you experience?
>     
>     So did anyone test and okay with committing to 4.13.2? How can I do it? Rebase my nosorting branch to 4.13.2 branch and then merge my nosorting branch with the two commits into 4.13.2 branch? I did so with my commits to master branch, so I think this would work.

Andras wrote:
> I updated master after the commit and didn't see any bad sideeffects. Can't
> tell if it is faster or not.

Okay, don´t see your comment on reviewboard. How large is your maildir?

find ~/.local/share/local-mail -type f

martin at merkaba:~> du -sh ~/.local/share/local-mail
11G     /home/martin/.local/share/local-mail
martin at merkaba:~> find ~/.local/share/local-mail -type f | wc -l
875128

Anyway, I will commit this to 4.13.2 in a few days if no one objects.


- Martin


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On May 5, 2014, 12:07 p.m., Martin Steigerwald wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/117975/
> -----------------------------------------------------------
> 
> (Updated May 5, 2014, 12:07 p.m.)
> 
> 
> 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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