From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id A53B06B003D for ; Thu, 26 Mar 2009 15:37:33 -0400 (EDT) Date: Thu, 26 Mar 2009 13:39:29 -0700 (PDT) Message-Id: <20090326.133929.157003101.davem@davemloft.net> Subject: Re: tlb_gather_mmu() and semantics of "fullmm" From: David Miller In-Reply-To: References: <1238043674.25062.823.camel@pasglop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: hugh@veritas.com Cc: benh@kernel.crashing.org, linux-mm@kvack.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, npiggin@suse.de, zach@vmware.com, jeremy@goop.org List-ID: From: Hugh Dickins Date: Thu, 26 Mar 2009 14:08:17 +0000 (GMT) > On Thu, 26 Mar 2009, Benjamin Herrenschmidt wrote: > > If it means the later (which it does in practice today, since we only > > call it from exit_mmap(), unless I missed an important detail), then I > > could implement some optimisations in my own arch code, but more > > Yes, I'm pretty sure you can assume the latter. The whole point > of the "full mm" stuff (would have better been named "exit mm") is > to allow optimizations, and I don't see what optimization there is to > be made from knowing you're going the whole length of the mm; whereas > optimizations can be made if you know nothing can happen in parallel. > > Cc'ed DaveM who introduced it for sparc64, and Zach and Jeremy > who have delved there, in case they wish to disagree. The TLBs on sparc64 have a "context flush" which removes every entry matching the current MMU context. This is what flush_tlb_mm() does. So we use tlb->fullmm so that the individual page and range TLB flushes do nothing, and instead we do a flush_tlb_mm() before we walk through the address space to tear it down. -- 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