From: David Miller <davem@davemloft.net>
To: torvalds@linux-foundation.org
Cc: linux-arch@vger.kernel.org, mingo@elte.hu,
benh@kernel.crashing.org, rmk@arm.linux.org.uk
Subject: Re: Software prefetching considered harmful
Date: Thu, 19 May 2011 15:32:59 -0400 (EDT) [thread overview]
Message-ID: <20110519.153259.1670240855485459381.davem@davemloft.net> (raw)
In-Reply-To: <BANLkTi=428+KWmDcHoFYs5gO_C9wyhxJnQ@mail.gmail.com>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 19 May 2011 12:05:31 -0700
> Added davem, benh and rmk explicitly - I think you're on linux-arch,
> but still.. You may have machines that like prefetch more, although I
> think the "pollute the L1 cache" issue means that even if you don't
> have the NULL pointer microtrap issue you'll still find this actually
> performs better..
It's been my experience that prefetch hurts more than it ever helps
for these list traversal functions.
In fact I had been looking at some assembler output for files in the
networking and noticed how all of these list prefetch turds just take
up I-cache space.
Please kill them off, you have my utmost support :-)
Acked-by: David S. Miller <davem@davemloft.net>
next prev parent reply other threads:[~2011-05-19 19:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-19 17:12 Software prefetching considered harmful Linus Torvalds
2011-05-19 19:05 ` Linus Torvalds
2011-05-19 19:28 ` Ingo Molnar
2011-05-21 3:37 ` Michael Cree
2011-05-21 4:18 ` Benjamin Herrenschmidt
2011-05-21 10:42 ` Ingo Molnar
2011-05-19 19:32 ` David Miller [this message]
2011-05-19 19:38 ` Linus Torvalds
2011-05-19 19:47 ` David Miller
2011-05-19 23:34 ` Ingo Molnar
2011-05-20 16:01 ` Catalin Marinas
2011-05-20 1:42 ` Benjamin Herrenschmidt
2011-05-20 8:34 ` Ingo Molnar
2011-05-20 9:13 ` Benjamin Herrenschmidt
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