Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753060AbaBYBmu (ORCPT ); Mon, 24 Feb 2014 20:42:50 -0500 Received: from mail-vc0-f174.google.com ([209.85.220.174]:48576 "EHLO mail-vc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456AbaBYBmt (ORCPT ); Mon, 24 Feb 2014 20:42:49 -0500 MIME-Version: 1.0 In-Reply-To: <1393290984.2577.5.camel@buesod1.americas.hpqcorp.net> References: <1392960523.3039.16.camel@buesod1.americas.hpqcorp.net> <1393016019.3039.40.camel@buesod1.americas.hpqcorp.net> <1393290984.2577.5.camel@buesod1.americas.hpqcorp.net> Date: Mon, 24 Feb 2014 17:42:48 -0800 X-Google-Sender-Auth: sfizCvEOtSfYyVOTjAwg7QqNsdQ Message-ID: Subject: Re: [PATCH] mm: per-thread vma caching From: Linus Torvalds To: Davidlohr Bueso Cc: Andrew Morton , Ingo Molnar , Peter Zijlstra , Michel Lespinasse , Mel Gorman , Rik van Riel , KOSAKI Motohiro , "Chandramouleeswaran, Aswin" , "Norton, Scott J" , linux-mm , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 24, 2014 at 5:16 PM, Davidlohr Bueso wrote: > > If we add the two missing bits to the shifting and use PAGE_SHIFT (x86 > at least) we get just as good results as with 10. So we would probably > prefer hashing based on the page number and not some offset within the > page. So just int idx = (addr >> PAGE_SHIFT) & 3; works fine? That makes me think it all just wants to be maximally spread out to approximate some NRU when adding an entry. Also, as far as I can tell, "vmacache_update()" should then become just a simple unconditional int idx = (addr >> PAGE_SHIFT) & 3; current->vmacache[idx] = newvma; because your original code did + if (curr->vmacache[idx] != newvma) + curr->vmacache[idx] = newvma; and that doesn't seem to make sense, since if "newvma" was already in the cache, then we would have found it when looking up, and we wouldn't be here updating it after doing the rb-walk? And with the per-mm cache removed, all that should remain is that simple version, no? You don't even need the "check the vmcache sequence number and clear if bogus", because the rule should be that you have always done a "vmcache_find()" first, which should have done that.. Anyway, can you send the final cleaned-up and simplfied (and re-tested) version? There's enough changes discussed here that I don't want to track the end result mentally.. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/