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From: Andi Kleen <ak@muc.de>
To: John Reiser <jreiser@BitWagon.com>
Cc: Andi Kleen <ak@muc.de>, Mikael Pettersson <mikpe@csd.uu.se>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH][3/7] perfctr-2.7.2 for 2.6.6-mm2: x86_64
Date: 15 May 2004 22:49:57 +0200	[thread overview]
Date: Sat, 15 May 2004 22:49:57 +0200	[thread overview]
Message-ID: <20040515204957.GB37274@colin2.muc.de> (raw)
In-Reply-To: <40A68056.6090606@BitWagon.com>

> I want the kernel to avoid every delay that can be avoided.  Do not force

There are a lot of other more frutiful targets I would focus my 
attention then.  e.g. you could get rid of __SLOW_DOWN_IO on modern 
machines which hits all the time and is a *lot* slower than even hundreds 
of pipeline flushes. Or of all the mdelays in driver code like IDE.

> a pipeline flush for speculative rdtsc.  Besides those 20-30 cycles

But how useful is the "work" when it results in wrong answers? 

Speculative RDTSC is not a theoretical problem, it has actually
caused problems in practice in other codes by making CPU timestamps
non monotonic.

-Andi

  reply	other threads:[~2004-05-15 20:50 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-15 14:42 Mikael Pettersson
2004-05-15 19:16 ` Andi Kleen
2004-05-15 20:40   ` John Reiser
2004-05-15 20:49     ` Andi Kleen [this message]
  -- strict thread matches above, loose matches on Subject: below --
2004-05-16  9:58 Mikael Pettersson
2004-05-15 14:44 Mikael Pettersson
2004-05-15 19:26 ` Andi Kleen
     [not found] <1VLRr-38z-19@gated-at.bofh.it>
2004-05-14 15:14 ` Andi Kleen
2004-05-15  5:37   ` Bryan O'Sullivan
2004-05-15  9:09     ` Andi Kleen
2004-05-16  4:15       ` Bryan O'Sullivan
2004-05-14 14:11 Mikael Pettersson

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