From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 13 Mar 2007 05:11:09 -0800 From: Andrew Morton Subject: Re: [QUICKLIST 0/4] Arch independent quicklists V2 Message-Id: <20070313051109.3215104b.akpm@linux-foundation.org> In-Reply-To: <45F69287.8040509@yahoo.com.au> References: <20070313071325.4920.82870.sendpatchset@schroedinger.engr.sgi.com> <20070313005334.853559ca.akpm@linux-foundation.org> <45F65ADA.9010501@yahoo.com.au> <20070313035250.f908a50e.akpm@linux-foundation.org> <45F685C6.8070806@yahoo.com.au> <20070313041551.565891b5.akpm@linux-foundation.org> <45F68B4B.9020200@yahoo.com.au> <20070313044756.b45649ac.akpm@linux-foundation.org> <45F69287.8040509@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: clameter@sgi.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: > On Tue, 13 Mar 2007 23:01:11 +1100 Nick Piggin wrote: > Andrew Morton wrote: > >>On Tue, 13 Mar 2007 22:30:19 +1100 Nick Piggin wrote: > >>We don't actually have to zap_pte_range the entire page table in > >>order to free it (IIRC we used to have to, before the 4lpt patches). > > > > > > I'm trying to remember why we ever would have needed to zero out the pagetable > > pages if we're taking down the whole mm? Maybe it's because "oh, the > > arch wants to put this page into a quicklist to recycle it", which is > > all rather circular. > > > > It would be interesting to look at a) leave the page full of random garbage > > if we're releasing the whole mm and b) return it straight to the page allocator. > > Well we have the 'fullmm' case, which avoids all the locked pte operations > (for those architectures where hardware pt walking requires atomicity). I suspect there are some tlb operations which could be skipped in that case too. > However we still have to visit those to-be-unmapped parts of the page table > to find the pages and free them. So we still at least need to bring it into > cache for the read... at which point, the store probably isn't a big burden. It means all that data has to be written back. Yes, I expect it'll prove to be less costly than the initial load. -- 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