Bug 20054 – Showing large plain-text files is extremely slow

• Component: Layout and Rendering
• Status: RESOLVED DUPLICATE

[Benjamin Meyer]

What steps will reproduce the problem?
1. dd if=/dev/urandom of=/tmp/test.txt bs=1024 count=256
2. go to uri file:///tmp/test.txt

What is the expected output? What do you see instead?
Mozilla shows this file in about 1 second.

QtWebKit from Qt 4.4

Please provide any additional information below.
Showing this file takes about 60 seconds on my machine.

I tracked down the issue to the fact that in bidi.cpp we are calling nextBreakablePosition over and over which constructs a QTextBoundryFinder

[Benjamin Meyer]

I started hacking around and made a branch that passes all of the tests and re-uses the iterator when possible, but it is a bit of a hack and when you enable the other iterator caches there are three failures which doesn't make any sense...  And it can still crash an iterator is created, the string is deleted a new string is created at the same location in memory, but with a different lenght and a new iterator is created with it.  We should just see about re-using the same iterator upstream.

Branch:
http://code.staikos.net/cgi-bin/gitweb.cgi?p=webkit;a=shortlog;h=bmeyer/fasttext

Diff:
http://code.staikos.net/cgi-bin/gitweb.cgi?p=webkit;a=blobdiff;f=WebCore/platform/qt/TextBreakIteratorQt.cpp;h=94aafdba5e8fd2e261caa4b446756112e1a3c2c6;hp=88b96808650ed290ea328208157d2f965089d39e;hb=95c45c80fc64841cfc262facaba34750b9ca5138;hpb=af6eca2c5a5ec7e5a462ad211f8f1e3cb9bdef86

[Benjamin Meyer]

Probably worth looking into what the average length is.  Maybe we could get rid of the buffer

[Kenneth Rohde Christiansen]

There have recently been some commits that could improve this:

https://bugs.webkit.org/show_bug.cgi?id=29092

Can you tell me if this is still an issue?

[Jocelyn Turcotte]

Created attachment 44137 [details]
Large text file

Example generated using:
dd if=/dev/random bs=1024 count=256 | base64 > large.txt

The bug is still present, reloading this file locks the browser for 20 seconds, it loads instantly in firefox.

[Jocelyn Turcotte]

This bug has to be fixed for QtWebKit 2.0

[Andreas Kling]

*** This bug has been marked as a duplicate of bug 31719 ***

[Benjamin Meyer]

Shouldn't that one be a duplicate of this issue as this is the older issue?

[Andreas Kling]

I opted for keeping the other one since it had more useful information.