From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: Software prefetching considered harmful Date: Thu, 19 May 2011 15:32:59 -0400 (EDT) Message-ID: <20110519.153259.1670240855485459381.davem@davemloft.net> References: Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from shards.monkeyblade.net ([198.137.202.13]:52431 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933808Ab1ESTe6 (ORCPT ); Thu, 19 May 2011 15:34:58 -0400 In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: torvalds@linux-foundation.org Cc: linux-arch@vger.kernel.org, mingo@elte.hu, benh@kernel.crashing.org, rmk@arm.linux.org.uk From: Linus Torvalds 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