From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <439CF3B1.4050803@yahoo.com.au> Date: Mon, 12 Dec 2005 14:51:13 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [RFC 3/6] Make nr_pagecache a per zone counter References: <20051210005440.3887.34478.sendpatchset@schroedinger.engr.sgi.com> <20051210005456.3887.94412.sendpatchset@schroedinger.engr.sgi.com> <20051211183241.GD4267@dmt.cnet> <20051211194840.GU11190@wotan.suse.de> <20051211204943.GA4375@dmt.cnet> In-Reply-To: <20051211204943.GA4375@dmt.cnet> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Marcelo Tosatti Cc: Andi Kleen , Christoph Lameter , linux-kernel@vger.kernel.org, Hugh Dickins , linux-mm@kvack.org List-ID: Marcelo Tosatti wrote: > On Sun, Dec 11, 2005 at 08:48:40PM +0100, Andi Kleen wrote: > >>>By the way, why does nr_pagecache needs to be an atomic variable on UP systems? >> >>At least on X86 UP atomic doesn't use the LOCK prefix and is thus quite >>cheap. I would expect other architectures who care about UP performance >>(= not IA64) to be similar. > > > But in practice the variable does not need to be an atomic type for UP, but > simply a word, since stores are atomic on UP systems, no? > > Several arches seem to use additional atomicity instructions on > atomic functions: > Yeah, this is to protect from interrupts and is common to most load store architectures. It is possible we could have atomic_xxx_irq / atomic_xxx_irqsave functions for these, however I think nobody has yet demostrated the improvements outweigh the complexity that would be added. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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