From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Nick Piggin <npiggin@suse.de>, Jens Axboe <jens.axboe@oracle.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel@vger.kernel.org,
Ravikiran G Thirumalai <kiran@scalex86.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [rfc][patch] store-free path walking
Date: Wed, 7 Oct 2009 14:20:50 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.01.0910071417300.3432@localhost.localdomain> (raw)
In-Reply-To: <20091007210651.GB1656@one.firstfloor.org>
On Wed, 7 Oct 2009, Andi Kleen wrote:
>
> It won't double it, because there are many more cache lines from
> all kinds of other things in these paths.
Not all that many. The big part of the D$ is the hash table lookup in this
path.
> The point was just to hide the latency of fetching two at different
> times. The actual cache foot print is not that important, as long as
> it's not excessive
You're full of sh*t.
Every extra line you fetch pushes out another line. No amount of
prefetching will hide that. So stop spreading idiotic fairytales.
The best optimization is to not do the work at all. It really is that
simple. Prefetching as an optimization technique absolutely sucks.
Linus
next prev parent reply other threads:[~2009-10-07 21:22 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-06 6:49 Latest vfs scalability patch Nick Piggin
2009-10-06 10:14 ` Jens Axboe
2009-10-06 10:26 ` Jens Axboe
2009-10-06 11:10 ` Peter Zijlstra
2009-10-06 12:51 ` Jens Axboe
2009-10-06 12:26 ` Nick Piggin
2009-10-06 12:49 ` Jens Axboe
2009-10-07 8:58 ` [rfc][patch] store-free path walking Nick Piggin
2009-10-07 9:56 ` Jens Axboe
2009-10-07 10:10 ` Nick Piggin
2009-10-12 3:58 ` Nick Piggin
2009-10-12 5:59 ` Nick Piggin
2009-10-12 8:20 ` Jens Axboe
2009-10-12 11:00 ` Jens Axboe
2009-10-13 1:26 ` Christoph Hellwig
2009-10-13 1:52 ` Nick Piggin
2009-10-07 14:56 ` Linus Torvalds
2009-10-07 16:27 ` Linus Torvalds
2009-10-07 16:46 ` Nick Piggin
2009-10-07 19:25 ` Linus Torvalds
2009-10-07 20:34 ` Andi Kleen
2009-10-07 20:51 ` Linus Torvalds
2009-10-07 21:06 ` Andi Kleen
2009-10-07 21:20 ` Linus Torvalds [this message]
2009-10-07 21:57 ` Linus Torvalds
2009-10-07 22:22 ` Andi Kleen
2009-10-08 7:39 ` Nick Piggin
2009-10-09 17:53 ` Andi Kleen
2009-10-08 13:12 ` Denys Vlasenko
2009-10-09 7:47 ` Nick Piggin
2009-10-09 17:49 ` Andi Kleen
2009-10-07 16:29 ` Nick Piggin
2009-10-08 12:36 ` Nick Piggin
2009-10-08 12:57 ` Jens Axboe
2009-10-08 13:22 ` Nick Piggin
2009-10-08 13:30 ` Jens Axboe
2009-10-08 18:00 ` Peter Zijlstra
2009-10-09 4:04 ` Nick Piggin
2009-10-09 8:54 ` Jens Axboe
2009-10-09 9:51 ` Jens Axboe
2009-10-09 10:02 ` Nick Piggin
2009-10-09 10:08 ` Jens Axboe
2009-10-09 10:07 ` Nick Piggin
2009-10-09 3:50 ` Nick Piggin
2009-10-09 6:15 ` David Miller
2009-10-09 10:40 ` Nick Piggin
2009-10-09 11:09 ` Jens Axboe
2009-10-09 10:44 ` Nick Piggin
2009-10-09 10:48 ` Jens Axboe
2009-10-09 23:16 ` Paul E. McKenney
2009-10-15 10:08 ` Latest vfs scalability patch Anton Blanchard
2009-10-15 10:39 ` Nick Piggin
2009-10-15 10:46 ` Anton Blanchard
2009-10-15 10:53 ` Nick Piggin
2009-10-15 11:23 ` Anton Blanchard
2009-10-15 11:41 ` Nick Piggin
2009-10-15 11:48 ` Nick Piggin
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