On Fri, 2004-07-23 at 20:07, sarab fadhil wrote:
[snip detailed system and user information]
Thanks for that info. It's really nice not to have to ask for it :-) and
I'm sure it'll help the folks here figure out your problem.
> My problem is with the login which is slow,
> it may take 10 minutes for all 32 students to login
> together, of course some of them will login faster
> than the others.
That's rather odd. Does a single, isolated user login on the system when
it's otherwise unloaded take a more reasonable amount of time?
> However, once every one login the
> system speed is acceptable, of course loading Star
> Office is a slow even in a stand alone computer.
Loading the second and subsequent OpenOffice 1.1.2 instances on my LTSP
server often takes only 2 or 3 seconds. The first one takes up to 10
seconds, depending on whether or not the binaries are still cached in
RAM. I had to turn off the splash screen because it sometimes only got
time to half-finish drawing before the app's main window came up. So I
wouldn't think that slow loading times are something to expect. The
second and further OpenOffice/StartOffice instances should AFAIK load
quite quickly if you have enough RAM and sufficient network bandwidth.
> I am
> using KDE as a user interface. Any advice of how to
> speed up the system is appreciated.
The first step will probably be to start measuring what is taking the
time. I'd recommend running 'vmstat 1 | tee /tmp/vmstat_log' while the
users log in, as this provides some useful info on how hard the server
is working. Additionally, I'd fire up gkrellm, a handy system monitor
tool, to get a visual impression, and I'd have 'top' running to get
real-time summaries of what programs are using the memory and CPU time.
It'd also be helpful to run 'free -m' before and after all the users log
in (and a few times during, if you like) to get an impression of what
sort of pressure the memory is under.
If you could run
ps -eo pid,ppid,user,state,size,rss,wchan,cmd
before, during and after user logins (and save the output somewhere)
that'd be useful too, as that will among other things show if processes
are in uninterruptable sleep (which is usually because they're waiting
on disk I/O).
If you upload the vmstat output, the before and after 'free' output, ps
output, and any other monitoring info you think could be handy to a web
page and post your impressions about what the server seemed to be doing
during the login process, that'd be handy. Uploading a copy of the
output of 'dmesg' and a snippet of /var/log/messages that covers the
duration
Have you checked to make sure there isn't of the user login process
wouldn't hurt, either.
Of course, it's entirely possible that someone will be able to pop up
here and say "yeah, I've seen this...." - but in case they can't, it'd
probably be a good idea to collect this information. It's very hard to
diagnose general performance problems without at least that information.
I should note that the use of a 7200rpm SATA disk, presumably one
designed for general PC use, will not be helping your system performance
at all. Even if each client's apps aren't trying to do much on it, those
disks just aren't designed for heavy multitasking and it'll probably be
thrashing like crazy. I run RAID 5 across 4 250GB SATA disks here, and
the performance is pretty poor (but sufficient for our purposes, as it's
mostly write-once read-occasionally archival data). AFAIK current
'consumer' disks and SATA chipsets don't support tagged command queuing,
which means the disks have considerably less ability to reorder requests
in a way that's more efficient for their physical layout, so they'll
waste more time seeking - especially under heavy multi-user loads. There
are now 10k RPM SATA disks with TCQ support available, but controller
support for TCQ is far from universal and the disks are pricey. Still,
they're cheaper (and according to StorageReview, often faster) than many
SCSI disks.
Are your disks connected to a SATA RAID controller like a 3ware
Escalade, to an add-in SATA card, or to SATA connectors on the
motherboard? What chipset and SATA driver are you using?
The performance measures I've requested may help point out whether or
not the issue you're seeing is disk related, memory related, or
something else.
P.S: Does anybody here know of a tool like 'top' but for disk access -
something that can show what processes are doing the most IOs per second
and transferring the most data per second to and from the disks? It'd be
incredibly helpful here, but I've been unable to find anything that can
associate disk I/O with the processes that caused it. I understand it's
not an easy process because of the way the vfs and I/O systems are
designed, but I'm hoping there's something out there that can help.
--
Craig Ringer
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