From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 165866B005A for ; Fri, 19 Jun 2009 03:09:05 -0400 (EDT) Received: from toip5.srvr.bell.ca ([209.226.175.88]) by tomts43-srv.bellnexxia.net (InterMail vM.5.01.06.13 201-253-122-130-113-20050324) with ESMTP id <20090618115953.TKGV11189.tomts43-srv.bellnexxia.net@toip5.srvr.bell.ca> for ; Thu, 18 Jun 2009 07:59:53 -0400 Date: Thu, 18 Jun 2009 07:59:46 -0400 From: Mathieu Desnoyers Subject: Re: [this_cpu_xx V2 16/19] this_cpu: slub aggressive use of this_cpu operations in the hotpaths Message-ID: <20090618115946.GA11108@Krystal> References: <20090617203337.399182817@gentwo.org> <20090617203445.892030202@gentwo.org> <1245306801.12010.10.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1245306801.12010.10.camel@penberg-laptop> Sender: owner-linux-mm@kvack.org To: Pekka Enberg Cc: cl@linux-foundation.org, akpm@linux-foundation.org, linux-mm@kvack.org, Tejun Heo , mingo@elte.hu, rusty@rustcorp.com.au, davem@davemloft.net List-ID: * Pekka Enberg (penberg@cs.helsinki.fi) wrote: > On Wed, 2009-06-17 at 16:33 -0400, cl@linux-foundation.org wrote: > > Use this_cpu_* operations in the hotpath to avoid calculations of > > kmem_cache_cpu pointer addresses. > > > > It is not clear if this is always an advantage. > > > > On x86 there is a tradeof: Multiple uses segment prefixes against an > > address calculation and more register pressure. > > > > On the other hand the use of prefixes is necessary if we want to use > > Mathieus scheme for fastpaths that do not require interrupt disable. > > On an unrelated note, it sure would be nice if the SLUB allocator didn't > have to disable interrupts because then we could just get rid of the gfp > masking there completely. > The solution I had just gets rid of the irqoff for the fast path. The slow path still needs to disable interrupts. Mathieu > Pekka > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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