From: Pavel Machek <pavel@suse.cz>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@transmeta.com>, linux-kernel@vger.kernel.org
Subject: Re: [patch] [sched] x86 idle thread should clear %fs, %gs
Date: Tue, 29 Jan 2002 01:04:20 +0100 [thread overview]
Message-ID: <20020129000419.GA18496@elf.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.33.0201271826220.5785-100000@localhost.localdomain>
In-Reply-To: <Pine.LNX.4.33.0201271826220.5785-100000@localhost.localdomain>
Hi!
> so it appears that this lowlevel x86 performance bug(?) is more than 11
> years old! :-)
Probably 386's were not optimized for %fs==%gs==0 case?
BTW does it really make a difference for the CPU?
Pavel
> @@ -2803,9 +2803,10 @@
> load_TR(nr);
> load_LDT(&init_mm);
>
> - /*
> - * Clear all 6 debug registers:
> - */
> + /* Clear %fs and %gs. */
> + asm volatile ("xorl %eax, %eax; movl %eax, %fs; movl %eax, %gs");
> +
> + /* Clear all 6 debug registers: */
>
> #define CD(register) __asm__("movl %0,%%db" #register ::"r"(0) );
--
(about SSSCA) "I don't say this lightly. However, I really think that the U.S.
no longer is classifiable as a democracy, but rather as a plutocracy." --hpa
next prev parent reply other threads:[~2002-01-30 21:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-27 17:37 Ingo Molnar
2002-01-29 0:04 ` Pavel Machek [this message]
2002-01-31 11:33 ` Ingo Molnar
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