Bug 241339

Summary:	ktorrent-4.0: Heavy i/o with real downloading at low speed using xfs or btrfs
Product:	[Applications] ktorrent	Reporter:	Andriy M <sidius.ua>
Component:	general	Assignee:	Joris Guisson <joris.guisson>
Status:	RESOLVED FIXED
Severity:	normal	CC:	erik.schepers, fedor.duhovskoy
Priority:	NOR
Version:	unspecified
Target Milestone:	---
Platform:	Gentoo Packages
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Andriy M 2010-06-10 21:02:11 UTC

Version:           unspecified (using KDE 4.4.3) 
OS:                Linux

Heavy i/o with real downloading at low speed, when using ktorrent-4.0 and filesystem is xfs or btrfs (confirmed by another user). works flawlessly with ext4 though.

When I download to xfs partition ktorrent downloads only at 1 mb/s of 10-11 mb/s possible. Gui reacts very slow (takes up to 10 sec for button press reaction) during download process. If I change download directory to ext4 partition everything goes normal.
I also tried to download with other clients (qbittorrent and ktorrent-3.3.4) and everything is fine with xfs.

Here are words of btrfs user:
"For me on btrfs ktorrent was downloading at 1 mbit/s (128 kb/s) and responded wery bad to any interaction. also the most of cpu was wasted on waiting for i/o to disk (wait state in top). And in htop or top ktorrent was marked with D - which means it was waiting for io.
After changing download location to ext4 ktorrent went to 10 mbit/s, and was responding to my actions without any delays"

Reproducible: Always

Steps to Reproduce:
Start downloading something on xfs or btfs partition.

Actual Results:  
Heavy i/o with slow downloading (not utilizing all available bandwidth) with terrible gui lags

Expected Results:  
Normal downloading with fast gui reaction

Comment 1 Fedor 2010-06-10 21:38:59 UTC

I can confirm this with btrfs. Though i thought it's the btrfs's bug, not ktorrent, now i dunno.

Some extra info for my issue:
2.6.34-gentoo
Intel Celeron 430
Hard drives are connected to this:
00:1f.2 IDE interface: Intel Corporation 82801GB/GR/GH (ICH7 Family) SATA IDE Controller (rev 01)
One is 120 Gb ext4
Other is 500Gb btrfs

Everything is fine with ext4, and unsuable with btrfs
Disks are:
WDC WD1600JS-00MHB0
ST3500641AS

Comment 2 Joris Guisson 2010-06-10 22:09:02 UTC

It's about time everbody switched to ext4 :-)

KT 4.0 when mapping pieces of a file in memory will call posix_fallocate on that piece to ensure the diskspace is there. That way we can detect a disk getting full before attempting to write a piece to it.

However this is a rather slow operation for some file systems, and extremely fast for others. Strangely though according to http://log.amitshah.net/2009/03/comparison-of-file-systems-and-speeding.html, xfs and btrfs should be good at this operation.

I have already improved things somewhat, however this does not solve it under high write speeds. So I'm currently working on an alternate approach.

Comment 3 Fedor 2010-06-10 22:45:45 UTC

(In reply to comment #2)
> I have already improved things somewhat, however this does not solve it under
> high write speeds. So I'm currently working on an alternate approach.

Great, just let us know, when there will be something to test, i'll compile ktorrent form git/svn.

Comment 4 Joris Guisson 2010-06-12 10:06:01 UTC

SVN commit 1137278 by guisson:

Disable calling posix_fallocate before mapping chunk, it causes to much disk activity on some filesystems

BUG: 241339


 M  +1 -1      ChangeLog  
 M  +2 -0      src/diskio/cachefile.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1137278

Comment 5 Joris Guisson 2010-06-12 10:09:05 UTC

*** Bug 241154 has been marked as a duplicate of this bug. ***

Comment 6 Fedor 2010-06-12 16:07:56 UTC

(In reply to comment #4)
> SVN commit 1137278 by guisson:
> 
> Disable calling posix_fallocate before mapping chunk, it causes to much disk
> activity on some filesystems
> 
> BUG: 241339
> 
> 
>  M  +1 -1      ChangeLog  
>  M  +2 -0      src/diskio/cachefile.cpp  
> 
> 
> WebSVN link: http://websvn.kde.org/?view=rev&revision=1137278
That fixed this issue for me.

Comment 7 Andriy M 2010-06-12 20:08:23 UTC

I've just build ktorrent from svn and it downloads on xfs partition without any problems. Thanks.