LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Carlos R. Mafra" <crmafra2@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: ray-lk@madrabbit.org, linux-kernel@vger.kernel.org
Subject: Re: Interactivity issue in 2.6.25-rc3
Date: Fri, 29 Feb 2008 14:14:42 -0300	[thread overview]
Message-ID: <20080229171442.GA5173@localhost.ift.unesp.br> (raw)
In-Reply-To: <20080229160408.GG27248@elte.hu>

On Fri 29.Feb'08 at 17:04:08 +0100, Ingo Molnar wrote:
> 
> (on-list)
> 
> * Carlos R. Mafra <crmafra2@gmail.com> wrote:
> 
> > Is it an scheduler anomaly if 'se.wait_max' is bigger than 40 msecs 
> > for _any_ of the processes which appear in the debug script log? In 
> > other words, is the scheduler mathematically build to not allow 
> > latencies higher than 40 msecs?
> 
> it is definitely an anomaly if it's bigger than 40 msecs if you clear 
> all stats via cfs-debug-info-clear.sh and the large latencies appear 
> after that. You can force it to go above 40 msecs if you run more than 
> say 40 CPU hogs in parallel, so it's not "mathematical", but you should 
> never see large latencies under normal workloads - and that includes 
> almost everything but "insanely high" workloads.

Thank you for the explanation! 

> and obviously, even if you only 'feel' long delays that's too an anomaly 
> by definition, no matter what the scripts say about it. It might even be 
> a scheduler anomaly as well: for example if the scheduler clock has an 
> anomaly - on which the delay statistics are based too.

But if the scripts say all 'se.wait_max' are < 40 msecs than it is
not CFS' fault, right? Even if it takes 3 seconds for a typed letter
to appear in the terminal?

> generally, latencytop gives a pretty good idea about where app delays 
> come from. (As a second-level mechanism, in sched-devel.git you can try 
> the latency tracer.)

Yeah, I must try latencytop to check for more things before sending
an email reporting possible problems. 

Thanks again!

  reply	other threads:[~2008-02-29 17:13 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-28 18:44 Carlos R. Mafra
2008-02-28 19:18 ` Ingo Molnar
2008-02-28 19:54   ` Ray Lee
     [not found]     ` <20080228210627.GA4337@localhost.ift.unesp.br>
2008-02-28 21:28       ` Ray Lee
2008-02-29 15:57         ` Ingo Molnar
2008-02-29 18:33           ` Ray Lee
2008-02-29 16:04       ` Ingo Molnar
2008-02-29 17:14         ` Carlos R. Mafra [this message]
2008-02-29 18:36           ` Ingo Molnar
2008-02-28 21:21 Carlos R. Mafra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080229171442.GA5173@localhost.ift.unesp.br \
    --to=crmafra2@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=ray-lk@madrabbit.org \
    --subject='Re: Interactivity issue in 2.6.25-rc3' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).