From: ebiederm@xmission.com (Eric W. Biederman)
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Arjan van de Ven <arjan@infradead.org>,
Jakub Jelinek <jakub@redhat.com>,
Ulrich Drepper <drepper@redhat.com>,
Roland McGrath <roland@redhat.com>,
"Randy.Dunlap" <rdunlap@xenotime.net>,
akpm@osdl.org, linux-kernel@vger.kernel.org,
libc-alpha@sourceware.org
Subject: Re: [PATCH] Use uname not sysctl to get the kernel revision
Date: Wed, 12 Jul 2006 16:26:25 -0600 [thread overview]
Message-ID: <m1zmfe794e.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <44B57191.5000802@zytor.com> (H. Peter Anvin's message of "Wed, 12 Jul 2006 15:02:57 -0700")
"H. Peter Anvin" <hpa@zytor.com> writes:
> Arjan van de Ven wrote:
>>> It is a short busy wait before falling asleep. I assume you mean
>>> busy wait is a loss even on SMP?
>> eh yeah I forgot to think for a second. But yes even for SMP busy wait
>> is pretty bad power wise nowadays.. at least if you wait more than a few
>> hundred cycles. (and if you wait less... then it's almost unlikely that
>> it'll be useful as well)
>>
>
> It depends greatly; if a lock is likely to get released by the user after a few
> memory accesses, spinning is likely to be a win.
But this requires that the lock be short lived, and highly contended.
If the lock is not short lived then the release is like to be a long
ways off. If the lock is not highly contended then you are not likely
to hit the window when someone else as the contended lock.
How frequent are highly contended short lived locks in user space?
Eric
next prev parent reply other threads:[~2006-07-12 22:27 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-10 22:39 [PATCH] sysctl: Document that sys_sysctl will be removed Eric W. Biederman
2006-07-10 22:50 ` Randy.Dunlap
2006-07-11 4:10 ` Eric W. Biederman
2006-07-11 7:07 ` Arjan van de Ven
2006-07-12 16:25 ` [PATCH] Use uname not sysctl to get the kernel revision Eric W. Biederman
2006-07-12 16:50 ` Ulrich Drepper
2006-07-12 17:42 ` Eric W. Biederman
2006-07-12 23:24 ` Theodore Tso
2006-07-12 23:31 ` Andi Kleen
2006-07-13 0:12 ` Theodore Tso
2006-07-13 2:33 ` Eric W. Biederman
2006-07-13 12:15 ` Andi Kleen
2006-07-12 23:44 ` Steve Munroe
2006-07-14 18:49 ` Benjamin Herrenschmidt
2006-07-14 19:09 ` Andi Kleen
2006-07-13 0:19 ` Eric W. Biederman
2006-07-12 18:44 ` Roland McGrath
2006-07-12 19:33 ` Ulrich Drepper
2006-07-12 19:53 ` Jakub Jelinek
2006-07-12 20:09 ` H. Peter Anvin
2006-07-12 21:23 ` Eric W. Biederman
2006-07-12 21:29 ` Arjan van de Ven
2006-07-12 21:56 ` Eric W. Biederman
2006-07-12 22:01 ` Arjan van de Ven
2006-07-12 22:02 ` H. Peter Anvin
2006-07-12 22:26 ` Eric W. Biederman [this message]
2006-07-12 22:31 ` H. Peter Anvin
2006-07-12 23:07 ` Alan Cox
2006-07-12 23:19 ` H. Peter Anvin
2006-07-13 11:15 ` Alan Cox
2006-07-14 18:45 ` Benjamin Herrenschmidt
2006-07-14 19:11 ` H. Peter Anvin
2006-07-12 21:29 ` H. Peter Anvin
2006-07-12 21:33 ` Michael Tokarev
2006-07-13 5:17 ` Ulrich Drepper
2006-07-13 6:27 ` Ian Wienand
2006-07-13 14:39 ` Eric W. Biederman
2006-07-13 15:05 ` Arjan van de Ven
-- strict thread matches above, loose matches on Subject: below --
2006-07-13 5:00 Albert Cahalan
2006-07-13 5:42 ` H. Peter Anvin
2006-07-13 6:09 ` Albert Cahalan
2006-07-13 6:13 ` Albert Cahalan
2006-07-13 6:38 ` Eric W. Biederman
2006-07-13 16:15 ` Albert Cahalan
2006-07-13 16:53 ` Eric W. Biederman
2006-07-13 17:06 ` Albert Cahalan
2006-07-13 15:20 ` Eric W. Biederman
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