linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	Jens Axboe <jens.axboe@oracle.com>, Andi Kleen <ak@suse.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: x86: Is there still value in having a special tlb flush IPI vector?
Date: Fri, 1 Aug 2008 11:32:32 +1000	[thread overview]
Message-ID: <200808011132.32856.nickpiggin@yahoo.com.au> (raw)
In-Reply-To: <20080731164826.GH26393@elte.hu>

On Friday 01 August 2008 02:48, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:

> > The overhead of that is a smp_mb() and a list_empty() check in
> > generic_smp_call_function_single_interrupt() if there is indeed no
> > work to do.
>
> that would be a miniscule cost - cacheline is read-shared amongst cpus
> so there's no real bouncing there. So i'm all for it ...

smp_mb would cost some cycles. So would the branch mispredict because
list_empty would otherwise normally be taken I think. q likely is not
in cache either.

I'm not in favour.

  reply	other threads:[~2008-08-01  1:32 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-07-28 23:16 x86: Is there still value in having a special tlb flush IPI vector? Jeremy Fitzhardinge
2008-07-28 23:20 ` Jeremy Fitzhardinge
2008-07-29  2:12   ` Andi Kleen
2008-07-29  6:29     ` Jeremy Fitzhardinge
2008-07-29 12:02       ` Andi Kleen
2008-07-29 14:46         ` Jeremy Fitzhardinge
2008-07-29 14:58           ` Andi Kleen
2008-07-28 23:34 ` Ingo Molnar
2008-07-29  4:30   ` Nick Piggin
2008-07-29  6:19     ` Jeremy Fitzhardinge
2008-07-29  9:47       ` Nick Piggin
2008-07-29  9:54     ` Peter Zijlstra
2008-07-29 10:00       ` Nick Piggin
2008-07-29 10:04         ` Peter Zijlstra
2008-07-29 10:17           ` Nick Piggin
2008-07-29 10:23             ` Peter Zijlstra
2008-07-29 10:45         ` Peter Zijlstra
2008-07-31 16:48           ` Ingo Molnar
2008-08-01  1:32             ` Nick Piggin [this message]
2008-07-31 17:48           ` Jeremy Fitzhardinge
2008-07-31 20:57             ` Ingo Molnar
2008-07-31 21:15               ` Peter Zijlstra

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=200808011132.32856.nickpiggin@yahoo.com.au \
    --to=nickpiggin@yahoo.com.au \
    --cc=ak@suse.de \
    --cc=hpa@zytor.com \
    --cc=jens.axboe@oracle.com \
    --cc=jeremy@goop.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
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).