LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Rik van Riel <riel@redhat.com>
To: "J.C. Pizarro" <jcpiza@gmail.com>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: Please, put 64-bit counter per task and incr.by.one each ctxt switch.
Date: Sat, 23 Feb 2008 23:26:51 -0500	[thread overview]
Message-ID: <20080223232651.41dffa72@bree.surriel.com> (raw)
In-Reply-To: <998d0e4a0802232008w5c6566f0se15ab749ec6f1ceb@mail.gmail.com>

On Sun, 24 Feb 2008 05:08:46 +0100
"J.C. Pizarro" <jcpiza@gmail.com> wrote:

OK, one last reply on the (overly optimistic?) assumption that you are not a troll.

> +++ linux-2.6_git-20080224/include/linux/sched.h        2008-02-24
> 04:50:18.000000000 +0100
> @@ -1007,6 +1007,12 @@
>         struct hlist_head preempt_notifiers;
>  #endif
> 
> +       unsigned long long ctxt_switch_counts; /* 64-bit switches' count */
> +       /* ToDo:
> +        *  To implement a poller/clock for CPU-scheduler that only reads
> +        *   these counts of context switches of the runqueue's tasks.
> +        *  No problem if this poller/clock is not implemented. */

So you're introducing a statistic, but have not yet written any code
that uses it?

> +       p->ctxt_switch_counts = 0ULL; /* task's 64-bit counter inited 0 */

Because we can all read C, there is no need to tell people in comments
what the code does.  Comments are there to explain why the code does
things, if an explanation is needed.

> >  > I will explain your later why of it.
> >
> >
> > ... and explain exactly why the kernel needs this extra code.
> 
> One reason: for the objective of gain interactivity, it's an issue that
>  CFS fair scheduler lacks it.

Your patch does not actually help interactivity, because all it does
is add an irq spinlock in a hot path (bad idea) and a counter which
nothing reads.

-- 
All rights reversed.

  reply	other threads:[~2008-02-24  4:27 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-24  3:08 J.C. Pizarro
2008-02-24  3:17 ` Rik van Riel
2008-02-24  4:08   ` J.C. Pizarro
2008-02-24  4:26     ` Rik van Riel [this message]
2008-02-24 13:12       ` J.C. Pizarro
2008-02-24 17:53         ` Mike Galbraith
2008-02-25 20:34         ` Andrew Morton
2008-02-26 13:20           ` J.C. Pizarro
2008-02-26 13:41             ` Alexey Dobriyan
2008-02-24  5:08     ` Mike Galbraith

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=20080223232651.41dffa72@bree.surriel.com \
    --to=riel@redhat.com \
    --cc=jcpiza@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    --subject='Re: Please, put 64-bit counter per task and incr.by.one each ctxt switch.' \
    /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).