From: Linus Torvalds <torvalds@linux-foundation.org>
To: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org
Subject: Re: [PATCH]: Fix SMP-reordering race in mark_buffer_dirty
Date: Wed, 2 Apr 2008 15:51:56 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.00.0804021548440.14670@woody.linux-foundation.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0804030035550.15850@artax.karlin.mff.cuni.cz>
On Thu, 3 Apr 2008, Mikulas Patocka wrote:
>
> When I added memory reads around mfence, the combined result was worse
> than the sum of reads and mfence --- mfence alone 8 ticks, mfence+4reads
> 18 ticks.
Sorry, my test-program was buggy.
> mfence+writes scales linearly, i.e. mfence + 4 writes does 12 ticks.
I get different results now that I fixed my memop test. I get a loop with
reads and writes taking 3 cycles without mfence, and 21 cycles with (read
after, write before).
Linus
next prev parent reply other threads:[~2008-04-02 22:52 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-02 19:20 Mikulas Patocka
2008-04-02 19:44 ` Linus Torvalds
2008-04-02 21:03 ` Mikulas Patocka
2008-04-02 21:31 ` Linus Torvalds
2008-04-02 21:35 ` Linus Torvalds
2008-04-02 22:39 ` Mikulas Patocka
2008-04-02 22:51 ` Linus Torvalds [this message]
2008-04-02 22:35 ` Mikulas Patocka
2008-04-02 22:01 ` Andrew Morton
2008-04-02 22:07 ` Linus Torvalds
2008-04-02 22:53 ` Mikulas Patocka
2008-04-02 23:52 ` Linus Torvalds
2008-04-03 2:12 ` Andrew Morton
2008-04-03 14:34 ` Linus Torvalds
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