From: David Mosberger <davidm@napali.hpl.hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: Scalability enhancements for gettimeofday
Date: Tue, 08 Jun 2004 21:38:43 +0000 [thread overview]
Message-ID: <16582.12771.356969.526686@napali.hpl.hp.com> (raw)
In-Reply-To: <200405201205.57930.clameter@sgi.com>
>>>>> On Tue, 8 Jun 2004 11:32:46 -0700 (PDT), Christoph Lameter <christoph@lameter.com> said:
Christoph> This does not effect the update of last_itc which does
Christoph> not depend on any of the variables you mention. The
Christoph> dependency existed for last_nsec_offset but does NOT
Christoph> exist for last_itc. There is much more than just a name
Christoph> change going on.
Let me try this again: the second you update a global variable with a
bogus/inconsistent value, another CPU may observe that value. The
fact that you're going to try to correct that bad value later on
doesn't help you at all. See the problem now?
The fundamental issue is that with ITC-based interpolation, reading
the offset has a side-effect, which isn't true for global-timer-based
interpolation. Hence the need for a two-phase protocol.
--david
next prev parent reply other threads:[~2004-06-08 21:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-20 19:05 Scalability enhancements for gettimeofday Christoph Lameter
2004-06-02 17:33 ` David Mosberger
2004-06-02 20:58 ` John Hesterberg
2004-06-03 2:38 ` Jack Steiner
2004-06-03 4:56 ` Christoph Lameter
2004-06-03 16:28 ` Christoph Lameter
2004-06-03 20:04 ` Chris Wedgwood
2004-06-04 6:29 ` David Mosberger
2004-06-04 14:26 ` Christoph Lameter
2004-06-05 5:12 ` David Mosberger
2004-06-07 17:46 ` Christoph Lameter
2004-06-07 18:14 ` David Mosberger
2004-06-07 20:24 ` Christoph Lameter
2004-06-07 20:55 ` David Mosberger
2004-06-07 22:48 ` Christoph Lameter
2004-06-07 23:02 ` David Mosberger
2004-06-08 4:08 ` Christoph Lameter
2004-06-08 4:33 ` David Mosberger
2004-06-08 5:59 ` Christoph Lameter
2004-06-08 6:06 ` David Mosberger
2004-06-08 7:11 ` Christoph Lameter
2004-06-08 18:02 ` David Mosberger
2004-06-08 18:32 ` Christoph Lameter
2004-06-08 21:38 ` David Mosberger [this message]
2004-06-08 21:48 ` Christoph Lameter
2004-06-08 22:13 ` David Mosberger
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