From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <462D5A2E.5060908@yahoo.com.au> Date: Tue, 24 Apr 2007 11:15:26 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [PATCH] lazy freeing of memory through MADV_FREE References: <46247427.6000902@redhat.com> <20070420135715.f6e8e091.akpm@linux-foundation.org> <462932BE.4020005@redhat.com> <20070420150618.179d31a4.akpm@linux-foundation.org> <4629524C.5040302@redhat.com> <462ACA40.8070407@yahoo.com.au> <462B0156.9020407@redhat.com> <462BFAF3.4040509@yahoo.com.au> <462C2DC7.5070709@redhat.com> <462C2F33.8090508@redhat.com> <462C7A6F.9030905@redhat.com> <462C88B1.8080906@yahoo.com.au> <462C8B0A.8060801@redhat.com> <462C8BFF.2050405@yahoo.com.au> <462C8E1D.8000706@redhat.com> In-Reply-To: <462C8E1D.8000706@redhat.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: Andrew Morton , linux-kernel , linux-mm , shak , jakub@redhat.com, drepper@redhat.com List-ID: Rik van Riel wrote: > Use TLB batching for MADV_FREE. Adds another 10-15% extra performance > to the MySQL sysbench results on my quad core system. > > Signed-off-by: Rik van Riel > --- > > Nick Piggin wrote: > >>> 3) because of this, we can treat any such accesses as >>> happening simultaneously with the MADV_FREE and >>> as illegal, aka undefined behaviour territory and >>> we do not need to worry about them >> >> >> Yes, but I'm wondering if it is legal in all architectures. > > > It's similar to trying to access memory during an munmap. > > You may be able to for a short time, but it'll come back to > haunt you. The question is whether the architecture specific tlb flushing code will break or not. >>> 4) because we flush the tlb before releasing the page >>> table lock, other CPUs cannot remove this page from >>> the address space - they will block on the page >>> table lock before looking at this pte >> >> >> We don't when the ptl is split. > > > Even then we do. Each invocation of zap_pte_range() only touches > one page table page, and it flushes the TLB before releasing the > page table lock. What kernel are you looking at? -rc7 and rc6-mm1 don't, AFAIKS. -- SUSE Labs, Novell Inc. -- 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