From: Gabriel Paubert <paubert@iram.es>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Futex Asynchronous Interface
Date: Thu, 13 Jun 2002 18:38:22 +0200 [thread overview]
Message-ID: <3D08CA7E.9050704@iram.es> (raw)
In-Reply-To: <3D0776EE.4040701@loewe-komp.de> <Pine.LNX.4.44.0206120946100.22189-100000@home.transmeta.com>
Linus Torvalds wrote:
> Right now the kernel does _zero_ work for a lock that isn't contended. It
> doesn't know _anything_ about the process that got the lock initially.
>
> Any amount of tracking would be _extremely_ expensive. Right now getting
> an uncontended lock is about 15 CPU cycles in user space.
>
> Tryin to tell the kernel about gettign that lock takes about 1us on a P4
> (system call overhead), ie we're talking 18000 cycles. 18 THOUSAND cycles
> minimum. Compared to the current 15 cycles. That's more than three orders
> of magnitude slower than the current code, and you just lost the whole
> point of doing this all in user space in the first place.
Please tell us where you got your 18GHz CPU (18000 cycles/microsecond) ;-)
I want one, badly!
Gabriel
next prev parent reply other threads:[~2002-06-13 16:38 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-06 7:26 [PATCH] Futex Asynchronous Interface Rusty Russell
2002-06-02 0:10 ` Pavel Machek
2002-06-10 6:57 ` Rusty Russell
2002-06-06 16:36 ` Linus Torvalds
2002-06-06 19:27 ` Alan Cox
2002-06-06 23:21 ` Rusty Russell
2002-06-07 8:33 ` Peter Wächtler
2002-06-08 22:28 ` Linus Torvalds
2002-06-09 9:49 ` Kai Henningsen
2002-06-09 18:09 ` Linus Torvalds
2002-06-09 19:06 ` Thunder from the hill
2002-06-10 6:39 ` Kai Henningsen
2002-06-10 7:55 ` Helge Hafting
2002-06-10 14:10 ` Thunder from the hill
2002-06-10 20:46 ` Kai Henningsen
2002-06-11 14:14 ` john slee
2002-06-10 15:11 ` Linus Torvalds
2002-06-11 15:06 ` Eric W. Biederman
2002-06-10 20:57 ` H. Peter Anvin
2002-06-09 10:07 ` Peter Wächtler
2002-06-09 17:49 ` Linus Torvalds
2002-06-07 9:06 ` Rusty Russell
2002-06-08 22:42 ` Linus Torvalds
2002-06-11 9:15 ` Rusty Russell
2002-06-11 16:53 ` Linus Torvalds
2002-06-12 5:32 ` Rusty Russell
2002-06-12 9:16 ` Peter Wächtler
2002-06-12 14:19 ` Hubertus Franke
2002-06-12 16:50 ` Peter Wächtler
2002-06-12 18:15 ` Vladimir Zidar
2002-06-12 15:39 ` Linus Torvalds
2002-06-12 16:29 ` Peter Wächtler
2002-06-12 16:52 ` Linus Torvalds
2002-06-12 17:07 ` Peter Wächtler
2002-06-12 18:32 ` Saurabh Desai
2002-06-12 20:05 ` Oliver Xymoron
2002-06-12 20:16 ` Linus Torvalds
2002-06-13 2:57 ` Rusty Russell
2002-06-13 9:37 ` Peter Wächtler
2002-06-13 9:55 ` Rusty Russell
2002-06-13 16:38 ` Gabriel Paubert [this message]
2002-06-13 16:40 ` Linus Torvalds
2002-06-13 1:32 ` Rusty Russell
-- strict thread matches above, loose matches on Subject: below --
2002-06-06 16:08 Martin Wirth
2002-06-06 22:59 ` Rusty Russell
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