Bug 267297

Summary:	bad RAID disk performance
Product:	[Frameworks and Libraries] solid	Reporter:	wbrana
Component:	libsolid-udisks	Assignee:	Lukáš Tinkl <lukas>
Status:	RESOLVED INTENTIONAL
Severity:	normal	CC:	cfeck
Priority:	NOR
Version:	unspecified
Target Milestone:	---
Platform:	Gentoo Packages
OS:	Linux
Latest Commit:		Version Fixed In:

Description wbrana 2011-02-28 12:42:58 UTC

Version:           unspecified (using KDE 4.6.0) 
OS:                Linux

KDE is badly affecting performance of RAID10. 
dd is reading disk with speed 353 MB/s if system is booted with non-KDE e.g. IceWM.
If KDE is started, speed drops to approx. 180-190 MB/s. 
Any disk operations are obviously slower. 
Logout from KDE, don't restore speed.



Reproducible: Didn't try

Steps to Reproduce:
echo 3 > /proc/sys/vm/drop_caches
dd if=/dev/md2 of=/dev/null bs=4M count=128

Actual Results:  
128+0 records in
128+0 records out
536870912 bytes (537 MB) copied, 2.94772 s, 182 MB/s

Expected Results:  
128+0 records in
128+0 records out
536870912 bytes (537 MB) copied, 1.52247 s, 353 MB/s

Comment 1 Christoph Feck 2011-02-28 13:42:04 UTC

Can you check with "top" if there are any KDE processes consuming CPU cycles?

Comment 2 wbrana 2011-02-28 14:04:46 UTC

top is only process with non-zero CPU usage

Comment 3 wbrana 2011-03-01 16:52:27 UTC

I found that one of following daemons, which are started by KDE, is causing it.
/usr/libexec/udisks-daemon
/usr/libexec/upowerd
/usr/libexec/polkitd
After renaming, perf drop doesn't happen.

Comment 4 Christoph Feck 2011-03-01 17:09:13 UTC

Thanks for the update. Reassigning to solid developers for further inspection.

Comment 5 wbrana 2011-03-01 17:28:29 UTC

There is possibly related kernel bug
https://bugzilla.kernel.org/show_bug.cgi?id=15241

Comment 6 Lukáš Tinkl 2011-03-02 13:46:38 UTC

If it's udisks, you should really report it somewhere else :)