Re: anticipatory scheduling questions

From: Felipe Alfaro Solana (felipe_alfaro@linuxmail.org)
Date: Fri Feb 28 2003 - 09:38:11 EST


----- Original Message -----
From: Andrew Morton <akpm@digeo.com>
Date: Fri, 28 Feb 2003 04:44:07 -0800
To: "Felipe Alfaro Solana" <felipe_alfaro@linuxmail.org>
Subject: Re: anticipatory scheduling questions
 
> "Felipe Alfaro Solana" <felipe_alfaro@linuxmail.org> wrote:
> >
> > I have done benchmark tests with Evolution under the following conditions:
> > (times measured since the reply button is clicked until the message is
> > opened)
> >
> > 2.4.20-2.54 -> 9s
> > 2.5.63-mm1 w/Deadline -> 34s
> > 2.5.63-mm1 w/AS -> 33s
>
> Well something has gone quite wrong there. It sounds as if something in
> the 2.5 kernel has broken evolution.
>
> Does this happen every time you reply to a message or just the first time?
 
Only the first time.
 
> And if you reply to a message, then quit evolution, then restart evolution
> then reply to another message, does the same delay happen?
>
> The above tests will eliminate the IO system at least.
 
OK, it seems to me there's an IO delay here: The first time I reply to a message,
there is a continuous, steady and light disk load since I press the Reply button
until the message appears. There are no pauses or delays.
 
If I close the message window and then click Reply again, the window opens up
almost immediately. Also, if I exit Evolution completely (shut it down and run "killev"
to kill wombat and friends), and then open it up again, the Reply message procedure
is also immediate.
 
> If the delay is still there when all the needed datais in pagecache then
> please run `vmstat 1' during the operation and send the part of the trace
> from the period when the delay happens.
 
Maybe I did not express myself correctly in my previous message: there are no such
delays. Since the moment I click Reply for the very first time until the window opens up,
there is no disk idle time.
 
> I'd suggest that you launch evolution from the command line in an xterm so
> you can watch for any diagnostic messages.
 
I have done so: Evolution is a complex application with many interdependencies and is
not very prone to launch diagnostic messages to the console. Anyways, I haven't seen
any diagnostic message in the console. I still think there is something in the AS I/O scheduler
that is not working at full read throughput. Of course I'm no expert.
 
Thanks!

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