From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f176.google.com (mail-ig0-f176.google.com [209.85.213.176]) by kanga.kvack.org (Postfix) with ESMTP id 839F76B0032 for ; Thu, 15 Jan 2015 22:27:20 -0500 (EST) Received: by mail-ig0-f176.google.com with SMTP id b16so1487293igk.3 for ; Thu, 15 Jan 2015 19:27:20 -0800 (PST) Received: from resqmta-po-07v.sys.comcast.net (resqmta-po-07v.sys.comcast.net. [2001:558:fe16:19:96:114:154:166]) by mx.google.com with ESMTPS id p9si5643247icc.49.2015.01.15.19.27.18 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Thu, 15 Jan 2015 19:27:19 -0800 (PST) Date: Thu, 15 Jan 2015 21:27:14 -0600 (CST) From: Christoph Lameter Subject: Re: [PATCH v2 1/2] mm/slub: optimize alloc/free fastpath by removing preemption on/off In-Reply-To: <20150115203045.00e9fb73@grimm.local.home> Message-ID: References: <1421307633-24045-1-git-send-email-iamjoonsoo.kim@lge.com> <20150115171634.685237a4.akpm@linux-foundation.org> <20150115203045.00e9fb73@grimm.local.home> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Steven Rostedt Cc: Andrew Morton , Joonsoo Kim , Pekka Enberg , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jesper Dangaard Brouer , Thomas Gleixner , Peter Zijlstra On Thu, 15 Jan 2015, Steven Rostedt wrote: > profiling function tracing I discovered that accessing preempt_count > was actually quite expensive, even just to read. But it may not be as > bad since Peter Zijlstra converted preempt_count to a per_cpu variable. > Although, IIRC, the perf profiling showed the access to the %gs > register was where the time consuming was happening, which is what > I believe per_cpu variables still use. The %gs register is not used since the address of the per cpu area is available as one of the first fields in the per cpu areas. -- 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