From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id BD6386B003D for ; Fri, 8 Jan 2010 12:44:04 -0500 (EST) Date: Fri, 8 Jan 2010 11:43:41 -0600 (CST) From: Christoph Lameter Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() In-Reply-To: Message-ID: References: <20100104182429.833180340@chello.nl> <20100104182813.753545361@chello.nl> <20100105092559.1de8b613.kamezawa.hiroyu@jp.fujitsu.com> <28c262361001042029w4b95f226lf54a3ed6a4291a3b@mail.gmail.com> <20100105134357.4bfb4951.kamezawa.hiroyu@jp.fujitsu.com> <20100105143046.73938ea2.kamezawa.hiroyu@jp.fujitsu.com> <20100105163939.a3f146fb.kamezawa.hiroyu@jp.fujitsu.com> <20100106092212.c8766aa8.kamezawa.hiroyu@jp.fujitsu.com> <20100106115233.5621bd5e.kamezawa.hiroyu@jp.fujitsu.com> <20100106125625.b02c1b3a.kamezawa.hiroyu@jp.fujitsu.com> <1262969610.4244.36.camel@laptop> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Linus Torvalds Cc: Peter Zijlstra , KAMEZAWA Hiroyuki , Minchan Kim , "Paul E. McKenney" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "hugh.dickins" , Nick Piggin , Ingo Molnar List-ID: On Fri, 8 Jan 2010, Linus Torvalds wrote: > That's a huge jump. It's clear that the spinlock-based rwsem's simply > suck. The speculation gets rid of some additional mmap_sem contention, > but at least for two sockets it looks like the rwsem implementation was > the biggest problem by far. I'd say that the ticket lock sucks for short critical sections vs. a simple spinlock since it forces the cacheline into shared mode. > Of course, larger numbers of sockets will likely change the situation, but > at the same time I do suspect that workloads designed for hundreds of > cores will need to try to behave better than that benchmark anyway ;) Can we at least consider a typical standard business server, dual quad core hyperthreaded with 16 "cpus"? Cacheline contention will increase significantly there. > Because let's face it - if your workload does several million page faults > per second, you're just doing something fundamentally _wrong_. You may just want to get your app running and its trying to initialize its memory in parallel on all threads. Nothing wrong with that. -- 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