Red Hat Bugzilla – Bug 468044
latencytop: multi-second latency during system update
Last modified: 2009-12-18 01:37:31 EST
Created attachment 321164 [details]
latencytop capture #1
Description of problem:
latencytop reports multisecond latency that is consistent with system behaviour (jerky pointer movements, slow display updates)
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. open your favorite apps for the job of the day (thunderbird, firefox, pidgin, gnome-terminal(s))
2. do a system update
3. et voilà
Overloaded system with better interactive 'feel'
See latencytop screen captures.
I tried to mount my main partition using relatime option, but didn't notice any noticeable improvements.
$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Pentium(R) 4 CPU 2.80GHz
stepping : 9
cpu MHz : 2793.176
cache size : 512 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up pebs bts cid xtpr
bogomips : 5586.35
clflush size : 64
$ cat /proc/meminfo
MemTotal: 513216 kB
MemFree: 20044 kB
Buffers: 13688 kB
Cached: 147168 kB
SwapCached: 30856 kB
Active: 389156 kB
Inactive: 39524 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 513216 kB
LowFree: 20044 kB
SwapTotal: 1048568 kB
SwapFree: 926676 kB
Dirty: 120 kB
Writeback: 0 kB
AnonPages: 265048 kB
Mapped: 80100 kB
Slab: 29000 kB
SReclaimable: 13716 kB
SUnreclaim: 15284 kB
PageTables: 5256 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 1305176 kB
Committed_AS: 1079492 kB
VmallocTotal: 503800 kB
VmallocUsed: 2532 kB
VmallocChunk: 501124 kB
Hugepagesize: 4096 kB
DirectMap4k: 15808 kB
DirectMap4M: 507904 kB
from the looks of things, thunderbird is calling fsync. On ext3 this means a flush of all dirty pages, and a journal flush. With the yum update going on, you have a considerable number of pages waiting to be written out to disk.
I don't know thunderbird internals well enough to determine if it's doing fsync's excessively or not. Reassigning.
Created attachment 321242 [details]
latencytop capture #2
I don't particularly blame Thunderbird (see capture #2 from the same update run).
Anyway I understand that it might be related to ext3 journal syncing on disk as suggested in this article : http://kerneltrap.org/node/14148.
Is there really something kernel people can do about it or is this just a fact of life when dealing with journalled filesystems or ext3 particularly ? Would switching to ext4 or other fs help ?
How is this related to task scheduling and why the great work on CFS won't help in this case ?
I know, I know, every other OSe's insist that you leave any running program while updating the system. I may be a fool, but being able to update FC while working in a terminal on another machine without barely noticing would be really great. So I ask :-)
This report is not specifically restricted to fc10 beta or a particular kernel version as this has been the behaviour of every single FC instalment since my regular use of yum. Yes yum is a pig !
Just to add some more links:
* our firefox bug is bug 439908
* upstream firefox bug is https://bugzilla.mozilla.org/show_bug.cgi?id=421482
* kernel discussion is http://thread.gmane.org/gmane.comp.file-systems.ext4/6840/)
I am not sure, whether it is the same problem, but it may be good read.
Dave is this the same issue?
there are some pending kernel patches iirc to make ext3 better, but the fsync flaw is pretty much 'designed in' to ext3. ext4 should also improve somewhat if I understood correctly, but it's a little unproven right now.
a package update is going to create huge amounts of data to be written back to disk, so anything that fsyncs is going to cause this. The firefox bug was a problem because it called fsync so regularly (every page load). This is why I'm curious if thunderbird does anything excessive.
short answer: ext44
gah, jumpy touchpad.
short answer: ext3 sucks.
This bug appears to have been reported against 'rawhide' during the Fedora 10 development cycle.
Changing version to '10'.
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