Hi all, As a follow up to my previous post. I did some testing and have come to the conclusion that firefox is indeed at the heart of my problem re: high I/O wait times. See below.
On Wed, Mar 31, 2010 at 6:39 PM, john <lists.j...@gmail.com> wrote: > Oh, heck, I'll throw out another thing :-) > > I was surprised to see that there was so much disk write activity. I > am trying to figure out what is getting written where. I found a tool > called IOTOP that should correlate disk i/o to particular apps. > Unfortunately it uses some kernel hooks that aren't supported by > Ubuntu kernels so i am in the process of compiling an ubuntu kernel > with the proper stuff included. So I compiled a custom kernel by copying my .config and following directions here https://help.ubuntu.com/community/Kernel/Compile I turned enabled I/O accounting so that I could use IOTOP http://guichaz.free.fr/iotop/ CONFIG_TASK_IO_ACCOUNTING=y compiled the kernel and rebooted. IOTOP has a number of interesting features, including the ability to show all processes, all threads, only active process/threads, cumulative or real-time disk I/O etc. Running IOTOP while opening web pages in firefox, browsing, watching youtube etc, showed my that firefox does a LOT of disk writes and very few reads. Here's some sample output in with the "cumulative" switch turned on # iotop -a -P total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s PID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND 4423 be/3 root 12.00 K 1984.00 K 0.00 % 0.13 % [kjournald] 2581 be/3 root 0.00 B 636.00 K 0.00 % 0.03 % [kjournald] 5099 be/3 ntp 12.00 K 4.00 K 0.00 % 0.00 % ntpd -p /var/run/ntpd.pid -u 115:127 -g 10442 be/4 john 8.00 K 0.00 B 0.00 % 0.00 % gnome-terminal 7207 be/4 john 16.00 K 0.00 B 0.00 % 0.00 % gnome-panel --sm-client-id default1 10688 be/4 john 4.00 K 17.20 M 0.00 % 0.00 % firefox-bin 7172 be/4 john 0.00 B 336.00 K 0.00 % 0.00 % gconfd-2 11 5005 be/4 syslog 0.00 B 52.00 K 0.00 % 0.00 % syslogd -u syslog 5623 be/4 root 0.00 B 180.00 K 0.00 % 0.00 % winbindd In 10 minutes of futzing about firefox wrote 17.2 M to disk and read off 4K. All the writing apparently happens in the users ./mozilla directory. Indeed of the 47Gigs used on my disk 26Gigs (55%) are given over to my 570 users firefox profiles (eg ~45 M per user). The space isn't a problem, but I am really beginning to think all of that disk activity is really hurting our performance. I often feel like some of the best aspects of LTSP are nullified by Firefox's affect on the multi-user environment. At the same time I like firefox as a web-browser. I would love to find a way to make firefox feel like less of a liability, perhaps pushing /home to a faster disk will do that. I think Firefox's problems under LTSP really color our users perception of the usefulness of LTSP/ubuntu. Perhaps I just don't know how to configure Firefox correctly... I have followed https://help.ubuntu.com/community/UbuntuLTSP/Firefox3Optimize and I hope that it will make a difference. I am also going to mount /home on a separate disk either under raid 0 or 10 and/or perhaps buy a SAS or solid state disk. I am still mulling that one. I'm still interested in folks ideas about the "fastest" approach to take re: disk writes, and especially ideas about taming firefox under LTSP. Thanks to all for your ideas! John ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _____________________________________________________________________ Ltsp-discuss mailing list. To un-subscribe, or change prefs, goto: https://lists.sourceforge.net/lists/listinfo/ltsp-discuss For additional LTSP help, try #ltsp channel on irc.freenode.net
