From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx120.postini.com [74.125.245.120]) by kanga.kvack.org (Postfix) with SMTP id 578D46B0032 for ; Mon, 15 Jul 2013 19:08:04 -0400 (EDT) Date: Mon, 15 Jul 2013 16:08:02 -0700 From: Andrew Morton Subject: Re: [PATCH] mm/hugetlb: per-vma instantiation mutexes Message-Id: <20130715160802.9d0cdc0ee012b5e119317a98@linux-foundation.org> In-Reply-To: <20130715072432.GA28053@voom.fritz.box> References: <1373671681.2448.10.camel@buesod1.americas.hpqcorp.net> <1373858204.13826.9.camel@buesod1.americas.hpqcorp.net> <20130715072432.GA28053@voom.fritz.box> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Gibson Cc: Davidlohr Bueso , Hugh Dickins , Rik van Riel , Michel Lespinasse , Mel Gorman , Konstantin Khlebnikov , Michal Hocko , "AneeshKumarK.V" , KAMEZAWA Hiroyuki , Hillf Danton , linux-mm@kvack.org, LKML On Mon, 15 Jul 2013 17:24:32 +1000 David Gibson wrote: > I have previously proposed a correct method of improving scalability, > although it doesn't eliminate the lock. That's to use a set of hashed > mutexes. Yep - hashing the mutexes is an obvious and nicely localized way of improving this. It's a tweak, not a design change. The changelog should describe the choice of the hash key with great precision, please. It's important and is the first thing which reviewers and readers will zoom in on. Should the individual mutexes be cacheline aligned? Depends on the acquisition frequency, I guess. Please let's work through that. Let's not damage uniprocesor kernels too much. AFACIT the main offender here is fault_mutex_hash(), which is the world's most obfuscated "return 0;". > It wasn't merged before, but I don't recall the reasons > why. Me either. -- 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