From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:38550 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935110AbXGQVnQ (ORCPT ); Tue, 17 Jul 2007 17:43:16 -0400 Date: Tue, 17 Jul 2007 14:42:45 -0700 From: Andrew Morton Subject: Re: + sparc64-rename-tlb_flush_mmu.patch added to -mm tree Message-Id: <20070717144245.7760a716.akpm@linux-foundation.org> In-Reply-To: <20070717211445.GC16147@flint.arm.linux.org.uk> References: <200707170748.l6H7m1so005969@imap1.linux-foundation.org> <20070717005551.cdb9504e.akpm@linux-foundation.org> <20070717010324.833fee7e.akpm@linux-foundation.org> <1184680583.21357.67.camel@localhost> <20070717181843.GB16147@flint.arm.linux.org.uk> <20070717120820.86a50e75.akpm@linux-foundation.org> <20070717211445.GC16147@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org To: Russell King Cc: Martin Schwidefsky , linux-arch@vger.kernel.org, davem@davemloft.net, hugh@veritas.com List-ID: On Tue, 17 Jul 2007 22:14:45 +0100 Russell King wrote: > On Tue, Jul 17, 2007 at 12:08:20PM -0700, Andrew Morton wrote: > > On Tue, 17 Jul 2007 19:18:43 +0100 Russell King wrote: > > > > > On Tue, Jul 17, 2007 at 03:56:23PM +0200, Martin Schwidefsky wrote: > > > > On Tue, 2007-07-17 at 01:03 -0700, Andrew Morton wrote: > > > > > OK, I don't understand how this patch works - from a quick glance it > > > > > appears to be forgetting to flush stuff altogether on arm and arm26 at > > > > > least and I see no sign that Russell, Tony and Ian have even seen it. > > > > > > > > Added linux-arch so that affected arch-maintainers can comment. > > > > > > Having a little more information about Andrew's concern would be nice. > > > Under what circumstances do you think we're forgetting to flush stuff? > > > > > > > "quick glance". ARM's tlb_flush_mmu() becomes a no-op and I though that > > some real tlb_finish_mmu() got replaced by that. But I didn't look very > > closely. > > I don't think ARM will have a problem with this change. > > In the fullmm case, tlb_finish_mmu() will flush the entire mm, so > missing out the flush for each chunk is itself a worthwhile optimisation. > > In the !fullmm case, tlb_finish_mmu() does nothing as far as flushing > is concerned, and in any case does nothing with it's start and end > variables. > > So I think this patch suits us just fine. umm, OK, well what is the spec for this new interface which Martin is proposing to add? It _seems_ to be that if the arch implements tlb_flush_mmu() then its tlb_finish_mmu() can (should) be a no-op? Or if the arch's tlb_finish_mmu() does a full mm "flush" (god I hate that term - here we meant writeback, and perhaps invalidate??)) then its tlb_flush_mmu() can (should) be a no-op. Or something like that. Martin, I'd suggest that an update to Documentation/cachetlb.txt is in order, spell this all out. Doing this properly would require that Documentation/cachetlb.txt say something about tlb_gather_mmu() and tlb_finish_mmu() too, I guess. Please ;)