From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77310C04AB7 for ; Tue, 14 May 2019 14:41:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B4462085A for ; Tue, 14 May 2019 14:41:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557844869; bh=JvSWtBN2a+2LHm1ldZpeI1ZSDbBLbXB9nRK81ty/lvI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=xjfUtlVEjKRLJdP+buGCQ64Xb15JagpP+09OCSC1S4KPp81QQj5m9yPuyvJfm79tS 1O1lwqklEsRHgc1LClyb2+4wHb4u+gRXMzPeSC6P0Zm0ZYsdGKDzoc+MtXrko7LRV0 wAmlPnzcsd/54Cd5VXrdn9jdpSPg0INpiowMx/T4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726568AbfENOlI (ORCPT ); Tue, 14 May 2019 10:41:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:33148 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726151AbfENOlH (ORCPT ); Tue, 14 May 2019 10:41:07 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 16AAFAC38; Tue, 14 May 2019 14:41:06 +0000 (UTC) Date: Tue, 14 May 2019 16:41:05 +0200 From: Michal Hocko To: Oleksandr Natalenko Cc: linux-kernel@vger.kernel.org, Kirill Tkhai , Vlastimil Babka , Matthew Wilcox , Pavel Tatashin , Timofey Titovets , Aaron Tomlin , Grzegorz Halat , linux-mm@kvack.org, linux-api@vger.kernel.org Subject: Re: [PATCH RFC v2 0/4] mm/ksm: add option to automerge VMAs Message-ID: <20190514144105.GF4683@dhcp22.suse.cz> References: <20190514131654.25463-1-oleksandr@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190514131654.25463-1-oleksandr@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [This is adding a new user visible interface so you should be CCing linux-api mailing list. Also CC Hugh for KSM in general. Done now] On Tue 14-05-19 15:16:50, Oleksandr Natalenko wrote: > By default, KSM works only on memory that is marked by madvise(). And the > only way to get around that is to either: > > * use LD_PRELOAD; or > * patch the kernel with something like UKSM or PKSM. > > Instead, lets implement a sysfs knob, which allows marking VMAs as > mergeable. This can be used manually on some task in question or by some > small userspace helper daemon. > > The knob is named "force_madvise", and it is write-only. It accepts a PID > to act on. To mark the VMAs as mergeable, use: > > # echo PID > /sys/kernel/mm/ksm/force_madvise > > To unmerge all the VMAs, use the same approach, prepending the PID with > the "minus" sign: > > # echo -PID > /sys/kernel/mm/ksm/force_madvise > > This patchset is based on earlier Timofey's submission [1], but it doesn't > use dedicated kthread to walk through the list of tasks/VMAs. Instead, > it is up to userspace to traverse all the tasks in /proc if needed. > > The previous suggestion [2] was based on amending do_anonymous_page() > handler to implement fully automatic mode, but this approach was > incorrect due to improper locking and not desired due to excessive > complexity. > > The current approach just implements minimal interface and leaves the > decision on how and when to act to userspace. Please make sure to describe a usecase that warrants adding a new interface we have to maintain for ever. > > Thanks. > > [1] https://lore.kernel.org/patchwork/patch/1012142/ > [2] http://lkml.iu.edu/hypermail/linux/kernel/1905.1/02417.html > > Oleksandr Natalenko (4): > mm/ksm: introduce ksm_enter() helper > mm/ksm: introduce ksm_leave() helper > mm/ksm: introduce force_madvise knob > mm/ksm: add force merging/unmerging documentation > > Documentation/admin-guide/mm/ksm.rst | 11 ++ > mm/ksm.c | 160 +++++++++++++++++++++------ > 2 files changed, 137 insertions(+), 34 deletions(-) > > -- > 2.21.0 > -- Michal Hocko SUSE Labs