From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Sep 2005 08:42:22 -0700 (PDT) From: Christoph Lameter Subject: Re: Hugh's alternate page fault scalability approach on 512p Altix In-Reply-To: <20660000.1126103324@[10.10.2.4]> Message-ID: References: <20660000.1126103324@[10.10.2.4]> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: "Martin J. Bligh" Cc: torvalds@osdl.org, akpm@osdl.org, nickpiggin@yahoo.com.au, hugh@veritas.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, 7 Sep 2005, Martin J. Bligh wrote: > > Anticipatory prefaulting raises the highest fault rate obtainable three-fold > > through gang scheduling faults but may allocate some pages to a task that are > > not needed. > > IIRC that costed more than it saved, at least for forky workloads like a > kernel compile - extra cost in zap_pte_range etc. If things have changed > substantially in that path, I guess we could run the numbers again - has > been a couple of years. Right. The costs come about through wrong anticipations installing useless mappings. The patches that I posted have this feature off by default. Gang scheduling can be enabled by modifying a value in /proc. But I guess the approach is essentially dead unless others want this feature too. The current page fault scalability approach should be fine for a couple of years and who knows what direction mmu technology has taken then. -- 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