From: Andi Kleen <ak@suse.de>
To: Arjan van de Ven <arjan@infradead.org>
Cc: eranian@hpl.hp.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] x86-64 TIF flags for debug regs and io bitmap in ctxsw
Date: Tue, 4 Jul 2006 10:09:31 +0200 [thread overview]
Message-ID: <200607041009.31588.ak@suse.de> (raw)
In-Reply-To: <1151999509.3109.6.camel@laptopd505.fenrus.org>
On Tuesday 04 July 2006 09:51, Arjan van de Ven wrote:
> > - }
> > - }
> > + if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW))
> > + || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))
> > + __switch_to_xtra(prev_p, next_p, tss);
>
> well isn't this replacing an if() (which isn't cheap but also not
> expensive, due to unlikely()) with an atomic operation (which *is*
> expensive) ?
Where do you see an atomic operation?
Also on x86-64 unlikely is an no-op.
-Andi
next prev parent reply other threads:[~2006-07-04 8:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-04 7:28 [PATCH 1/2] x86-64 TIF flags for debug regs and io bitmap in ctxsw Stephane Eranian
2006-07-04 7:51 ` Arjan van de Ven
2006-07-04 8:09 ` Andi Kleen [this message]
2006-07-04 8:22 ` Arjan van de Ven
2006-07-04 8:10 ` Stephane Eranian
2006-07-04 8:14 ` Stephane Eranian
2006-07-04 8:14 ` Andi Kleen
2006-07-04 8:20 ` Stephane Eranian
-- strict thread matches above, loose matches on Subject: below --
2006-07-04 9:05 Mikael Pettersson
2006-07-04 10:22 ` Andi Kleen
2006-07-04 9:20 Mikael Pettersson
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