All of lore.kernel.org
 help / color / mirror / Atom feed
From: Con Kolivas <kernel@kolivas.org>
To: malc <av1474@comtv.ru>
Cc: Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org
Subject: Re: CPU load
Date: Wed, 14 Feb 2007 19:09:09 +1100	[thread overview]
Message-ID: <200702141909.09848.kernel@kolivas.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0702141023000.672@home.oyster.ru>

On Wednesday 14 February 2007 18:28, malc wrote:
> On Wed, 14 Feb 2007, Con Kolivas wrote:
> > On Wednesday 14 February 2007 09:01, malc wrote:
> >> On Mon, 12 Feb 2007, Pavel Machek wrote:
> >>> Hi!
>
> [..snip..]
>
> >>> I have (had?) code that 'exploits' this. I believe I could eat 90% of
> >>> cpu without being noticed.
> >>
> >> Slightly changed version of hog(around 3 lines in total changed) does
> >> that easily on 2.6.18.3 on PPC.
> >>
> >> http://www.boblycat.org/~malc/apc/load-hog-ppc.png
> >
> > I guess it's worth mentioning this is _only_ about displaying the cpu
> > usage to userspace, as the cpu scheduler knows the accounting of each
> > task in different ways. This behaviour can not be used to exploit the cpu
> > scheduler into a starvation situation. Using the discrete per process
> > accounting to accumulate the displayed values to userspace would fix this
> > problem, but would be expensive.
>
> Guess you are right, but, once again, the problem is not so much about
> fooling the system to do something or other, but confusing the user:

Yes and I certainly am not arguing against that.

>
> a. Everything is fine - the load is 0%, the fact that the system is
>     overheating and/or that some processes do not do as much as they
>     could is probably due to the bad hardware.
>
> b. The weird load pattern must be the result of bugs in my code.
>     (And then a whole lot of time/effort is poured into fixing the
>      problem which is simply not there)
>
> The current situation ought to be documented. Better yet some flag can
> be introduced somewhere in the system so that it exports realy values to
> /proc, not the estimations that are innacurate in some cases (like hog)

I wouldn't argue against any of those either. schedstats with userspace tools 
to understand the data will give better information I believe.

-- 
-ck

  reply	other threads:[~2007-02-14  8:10 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-12  5:33 Vassili Karpov
2007-02-12  5:44 ` Con Kolivas
2007-02-12  5:54   ` malc
2007-02-12  6:12     ` Con Kolivas
2007-02-12  7:10       ` malc
2007-02-12  7:29         ` Con Kolivas
2007-02-12  5:55   ` Stephen Rothwell
2007-02-12  6:08     ` Con Kolivas
2007-02-12 14:32   ` Pavel Machek
2007-02-13 22:01     ` malc
2007-02-13 22:08       ` Con Kolivas
2007-02-14  7:28         ` malc
2007-02-14  8:09           ` Con Kolivas [this message]
2007-02-14 20:45           ` Pavel Machek
2007-02-25 10:35             ` malc
2007-02-26  9:28               ` Pavel Machek
2007-02-26 10:42                 ` malc
2007-02-26 16:38                   ` Randy Dunlap
2007-02-12 18:05   ` malc
  -- strict thread matches above, loose matches on Subject: below --
2018-03-27 11:44 CPU Load Ryan Meulenkamp
2018-03-29  1:24 ` Andre McCurdy
2018-03-29  6:42   ` Jussi Laako
2007-02-12 16:57 CPU load Andrew Burgess
2007-02-12 18:15 ` malc
2002-07-10 14:50 David Chow
2002-07-10 16:54 ` William Lee Irwin III
2002-07-10 17:49   ` Robert Love
2002-07-26 17:38     ` David Chow

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=200702141909.09848.kernel@kolivas.org \
    --to=kernel@kolivas.org \
    --cc=av1474@comtv.ru \
    --cc=linux-kernel@vger.kernel.org \
    --cc=pavel@ucw.cz \
    --subject='Re: CPU load' \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.