From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: John Hawkes <hawkes@sgi.com>
Cc: Arjan van de Ven <arjan@infradead.org>,
Tony Luck <tony.luck@gmail.com>, Andrew Morton <akpm@osdl.org>,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
Jack Steiner <steiner@sgi.com>, Dan Higgins <djh@sgi.com>,
Jeremy Higdon <jeremy@sgi.com>
Subject: Re: [PATCH] ia64: change usermode HZ to 250
Date: Wed, 28 Jun 2006 17:21:08 +0100 [thread overview]
Message-ID: <1151511668.15166.34.camel@localhost.localdomain> (raw)
In-Reply-To: <005e01c69ac9$a55e1bf0$6f00a8c0@comcast.net>
Ar Mer, 2006-06-28 am 08:43 -0700, ysgrifennodd John Hawkes:
> > #define HZ sysconf(_SC_CLK_TCK)
>
> That did occur to me. It obviously does get the correct value. The downside
> is that one of those crufty apps that thinks it is using "HZ" as a constant
> will instead be invoking a more costly syscall. Should we care about the
> resulting performance impact?
Given that HZ can be cached by glibc the performance impact is minimal
for most cases. The bigger problem will be code that does things with HZ
that only work on compile time evaluation. At least for those you'll
break at compile time.
Either way its kind of irrelevant, the ABI set HZ. Its done, there are
plenty of ways to change the kernel HZ without confusing userspace.
Alan
next prev parent reply other threads:[~2006-06-28 16:05 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-27 22:01 [PATCH] ia64: change usermode HZ to 250 hawkes
2006-06-28 8:39 ` Arjan van de Ven
2006-06-28 15:43 ` John Hawkes
2006-06-28 16:21 ` Alan Cox [this message]
2006-06-28 16:11 ` John Daiker
2006-06-28 16:50 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2006-06-27 22:26 Luck, Tony
2006-06-27 23:09 ` Lee Revell
2006-06-28 8:43 ` Arjan van de Ven
2006-06-28 10:47 ` Alan Cox
2006-06-28 10:34 ` Arjan van de Ven
2006-06-28 14:46 ` Christoph Lameter
2006-06-28 17:36 Luck, Tony
2006-06-29 9:37 ` Jes Sorensen
2006-06-29 11:02 ` Alan Cox
2006-06-29 10:48 ` Jes Sorensen
2006-06-29 10:55 ` Arjan van de Ven
2006-06-29 12:56 ` Jes Sorensen
2006-07-08 0:14 ` Jeremy Higdon
2006-07-08 2:51 ` Tony Luck
2006-07-08 6:42 ` Arjan van de Ven
2006-07-08 13:07 ` David Mosberger-Tang
2006-07-10 20:22 ` Jeremy Higdon
2006-07-11 3:01 ` David Mosberger-Tang
2006-07-11 10:10 ` Alan Cox
2006-07-11 18:37 ` Jeremy Higdon
2006-07-12 2:02 ` David Mosberger-Tang
2006-06-29 11:34 ` Alan Cox
2006-06-29 14:09 Albert Cahalan
2006-07-09 19:18 Luck, Tony
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