From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f50.google.com (mail-pb0-f50.google.com [209.85.160.50]) by kanga.kvack.org (Postfix) with ESMTP id DC3FC6B0031 for ; Fri, 7 Mar 2014 15:54:48 -0500 (EST) Received: by mail-pb0-f50.google.com with SMTP id md12so4679166pbc.9 for ; Fri, 07 Mar 2014 12:54:48 -0800 (PST) Received: from mail-pd0-x232.google.com (mail-pd0-x232.google.com [2607:f8b0:400e:c02::232]) by mx.google.com with ESMTPS id vo7si9458346pab.219.2014.03.07.12.54.47 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 07 Mar 2014 12:54:47 -0800 (PST) Received: by mail-pd0-f178.google.com with SMTP id x10so4509427pdj.37 for ; Fri, 07 Mar 2014 12:54:47 -0800 (PST) Date: Fri, 7 Mar 2014 12:54:45 -0800 (PST) From: David Rientjes Subject: Re: [PATCH] mempool: add unlikely and likely hints In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Mikulas Patocka Cc: Ingo Molnar , linux-mm@kvack.org On Fri, 7 Mar 2014, Mikulas Patocka wrote: > > What observable performance benefit have you seen with this patch and > > with what architecture? Could we include some data in the changelog? > > None - you usually don't get observable performance benefit from > microoptimizations like this. > > It may be that the cache line that the patch saves aliases some other > important cache lines and then, the patch saves two cache line refills. > Or, the saved cache line doesn't alias anything important and then the > patch doesn't have any effect at all. It's not worth spending many days or > weeks trying to recreate a situation when the code cache is used in such a > way that the patch would help. > Not sure there's any benefit of merging the patch, then. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org