From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752463AbcEQMe3 (ORCPT ); Tue, 17 May 2016 08:34:29 -0400 Received: from mail-lf0-f54.google.com ([209.85.215.54]:33972 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124AbcEQMe1 (ORCPT ); Tue, 17 May 2016 08:34:27 -0400 Date: Tue, 17 May 2016 15:34:23 +0300 From: "Kirill A. Shutemov" To: Minchan Kim Cc: Vinayak Menon , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, dan.j.williams@intel.com, mgorman@suse.de, vbabka@suse.cz, kirill.shutemov@linux.intel.com, dave.hansen@linux.intel.com, hughd@google.com Subject: Re: [PATCH] mm: make fault_around_bytes configurable Message-ID: <20160517123423.GF9540@node.shutemov.name> References: <1460992636-711-1-git-send-email-vinmenon@codeaurora.org> <20160421170150.b492ffe35d073270b53f0e4d@linux-foundation.org> <5719E494.20302@codeaurora.org> <20160422094430.GA7336@node.shutemov.name> <20160509073251.GA5434@blaptop> <20160510024842.GC4426@bbox> <20160516141854.GA2361@blaptop> <20160516142900.GB9540@node.shutemov.name> <20160516145632.GA2342@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160516145632.GA2342@blaptop> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 16, 2016 at 11:56:32PM +0900, Minchan Kim wrote: > On Mon, May 16, 2016 at 05:29:00PM +0300, Kirill A. Shutemov wrote: > > > Kirill, > > > You wanted to test non-HW access bit system and I did. > > > What's your opinion? > > > > Sorry, for late response. > > > > My patch is incomlete: we need to find a way to not mark pte as old if we > > handle page fault for the address the pte represents. > > I'm sure you can handle it but my point is there wouldn't be a big gain > although you can handle it in non-HW access bit system. Okay, let's be > more clear because I don't have every non-HW access bit architecture. > At least, current mobile workload in ARM which I have wouldn't be huge > benefit. > I will say one more. > I tested the workload on quad-core system and core speed is not so slow > compared to recent other mobile phone SoC. Even when I tested the benchmark > without pte_mkold, the benefit is within noise because storage is really > slow so major fault is dominant factor. So, I decide test storage from eMMC > to eSATA. And then finally, I manage to see the a little beneift with > fault_around without pte_mkold. > > However, let's consider side-effect aspect from fault_around. > > 1. Increase slab shrinking compard to old > 2. high level vmpressure compared to old > > With considering that regressions on my system, it's really not worth to > try at the moment. > That's why I wanted to disable fault_around as default in non-HW access > bit system. Feel free to post such patch. I guess it's reasonable. > > Once this will be done, the number of page faults shouldn't be higher with > > fault-around enabled even on machines without hardware accessed bit. This > > will address performance regression with the patch on such machines. > > Although you solves that, I guess the benefit would be marginal in > some architectures but we should solve above side-effects. > > > > > I'll try to find time to update the patch soon. > > I hope you can solve above those regressions as well. The patch is posted. Please test. -- Kirill A. Shutemov