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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_MUTT autolearn=ham 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 4FAA0C07E85 for ; Fri, 7 Dec 2018 10:55:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0EEE62083D for ; Fri, 7 Dec 2018 10:55:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544180159; bh=+7AiQI9MXw+gQCsOSsPjm4BnKL6wTB43lxpzDDwUw9A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=tJL1DAYNAG8smPB42B6V7IL0OCRMbZriPDxE+pa/EvKbxUaBMLWYT4dgTkUHG22It j90OQwWdm/ys99fNwDl0fDTwgAeKqUE8NdZwXTk4jVmOXJEes5P/XPDhqErzRAKf5U C/WlcG1hExnvswUDk9xxSkxpU/aFsNZDGgGWrK14= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0EEE62083D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726039AbeLGKz6 (ORCPT ); Fri, 7 Dec 2018 05:55:58 -0500 Received: from mx2.suse.de ([195.135.220.15]:38856 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725987AbeLGKz5 (ORCPT ); Fri, 7 Dec 2018 05:55:57 -0500 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 BE1A1AF0E; Fri, 7 Dec 2018 10:55:55 +0000 (UTC) Date: Fri, 7 Dec 2018 11:55:54 +0100 From: Michal Hocko To: linux-api@vger.kernel.org Cc: Andrew Morton , Alexey Dobriyan , linux-mm@kvack.org, LKML , Dan Williams , David Rientjes , Jan Kara Subject: Re: [RFC PATCH 0/3] THP eligibility reporting via proc Message-ID: <20181207105554.GX1286@dhcp22.suse.cz> References: <20181120103515.25280-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181120103515.25280-1-mhocko@kernel.org> 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 On Tue 20-11-18 11:35:12, Michal Hocko wrote: > Hi, > this series of three patches aims at making THP eligibility reporting > much more robust and long term sustainable. The trigger for the change > is a regression report [1] and the long follow up discussion. In short > the specific application didn't have good API to query whether a particular > mapping can be backed by THP so it has used VMA flags to workaround that. > These flags represent a deep internal state of VMAs and as such they should > be used by userspace with a great deal of caution. > > A similar has happened for [2] when users complained that VM_MIXEDMAP is > no longer set on DAX mappings. Again a lack of a proper API led to an > abuse. > > The first patch in the series tries to emphasise that that the semantic > of flags might change and any application consuming those should be really > careful. > > The remaining two patches provide a more suitable interface to address [1] > and provide a consistent API to query the THP status both for each VMA > and process wide as well. Are there any other comments on these? I haven't heard any pushback so far so I will re-send with RFC dropped early next week. > > [1] http://lkml.kernel.org/r/http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com > [2] http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz > -- Michal Hocko SUSE Labs