[Bug 271217] New: Performance problem: After upgrade to KDE SC 4.6.2, Kmail has become very slow

[Guido Winkelmann]

https://bugs.kde.org/show_bug.cgi?id=271217

           Summary: Performance problem: After upgrade to KDE SC 4.6.2,
                    Kmail has become very slow
           Product: kmail
           Version: 1.13.6
          Platform: Gentoo Packages
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: kdepim-bugs at kde.org
        ReportedBy: guido-kdebugs at unknownsite.de


Version:           1.13.6 (using KDE 4.6.2) 
OS:                Linux

After I upgraded my installation of KDE SC from 4.6.0 to 4.6.2 last monday,
Kmail has become extremely slow. This slowness is notable throughout all parts
parts of the user interface: 
When I select an email folder, it takes several seconds (in extreme cases about
10) for the folder contents to be displayed. If the folder has received any new
messages since I last had it open, it will again take several seconds for the
new messages to appear in the list.
When I click on an email in the message list, it takes several seconds for the
email to be displayed.
When I use the mouse wheel in the message list or the email view, it takes
several seconds for it to start scrolling.
When I move the mouse over an item in the message or folder view, it takes a
few seconds for the item to be highlighted and a tooltip to be displayed. Same
goes for the menubar, the icon bar and just about any other widget in Kmails
UI.

This slowdown did not start gradually, but rather happened quite suddenly after
I upgraded from KDE SC 4.6.0 to 4.6.2. Kmail used to be quite snappy before
that.
No other KDE application (that I use) seems to have been affected by this.

Kmail does NOT cause any noticable CPU- or IO-load during this. (Or at least,
not more than it always did.)

Reproducible: Didn't try

Steps to Reproduce:
(Example)
Open Kmail.
Wait for it to poll all configured servers and finish downloading all new
messages.
Move the mouse cursor over an arbitrary element in the folder list.

Actual Results:  
After more than 5 seconds, the item gets highlighted.

Expected Results:  
The item should be highlighted within significantly less than 1 second. (More
like 0.3 seconds maximum)

I tried recompiling Kmail after the problems started, but that did not solve te
problem.

I have several POP3- and IMAP accounts configured.

I have several email folders, both local and remote, which contain more than
10000 messages.

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