From: Manfred Spraul <manfred@colorfullife.com>
To: Andi Kleen <ak@muc.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fast path context switch - microoptimize FPU reload
Date: Sun, 09 Mar 2003 18:15:09 +0100 [thread overview]
Message-ID: <3E6B769D.2040602@colorfullife.com> (raw)
Andi wrote:
>We don't need the lock prefix to test our local thread flags state.
>Unfortunately test_thread_flag currently always uses test_bit which
>has a LOCK on SMP, but that's unnecessary. LOCK is costly on P4,
>so it's a good idea to avoid it.
>
>
No, LOCK is required: the TIF_ flags word is also used for signal
delivery - writing without lock could corrupt state.
What about moving TIF_USEDFPU from the thread_info into
task_struct->flags? This flag word is only accessed by "current", no
special atomicity requirements.
--
Manfred
next reply other threads:[~2003-03-09 17:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-09 17:15 Manfred Spraul [this message]
2003-03-09 17:30 ` [PATCH] Fast path context switch - microoptimize FPU reload Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2003-03-09 16:39 Andi Kleen
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