From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 12 Dec 2005 09:57:31 -0200 From: Marcelo Tosatti Subject: Re: [RFC 3/6] Make nr_pagecache a per zone counter Message-ID: <20051212115731.GA3599@dmt.cnet> 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> <439CF3B1.4050803@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <439CF3B1.4050803@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andi Kleen , Christoph Lameter , linux-kernel@vger.kernel.org, Hugh Dickins , linux-mm@kvack.org List-ID: On Mon, Dec 12, 2005 at 02:51:13PM +1100, Nick Piggin wrote: > 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. Hi Nick, But nr_pagecache is not accessed at interrupt code, is it? It does not need to be an atomic type. -- 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