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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 C6D38C4741F for ; Thu, 5 Nov 2020 17:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A97E206F9 for ; Thu, 5 Nov 2020 17:07:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604596075; bh=3Kyflshbt2mcMt0wwh4rdIWIdw67mlefC1/HkrjqGZc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=uLwAxa2Dpt7k/q7Ddo20nKzTyjoanI+b6goJZkHsEZQ4cTfOfFb6u7FxHkFljSM19 egWbpLJgeaRn/7VFki3bG5Cb4sFCtwSxby2q7xXQeI1PnneKVN54ffhDEB8/KQ+pCo Xp7iH58CokcpsIYg7sBAlMEqfhxML4wZse5CqQBI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730805AbgKERHz (ORCPT ); Thu, 5 Nov 2020 12:07:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726801AbgKERHy (ORCPT ); Thu, 5 Nov 2020 12:07:54 -0500 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A697AC0613CF; Thu, 5 Nov 2020 09:07:54 -0800 (PST) Received: by mail-pj1-x1044.google.com with SMTP id g19so294640pji.0; Thu, 05 Nov 2020 09:07:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=a/G37s3/UjwAPE/W5DNIRy/pjvBqWVcyDTzt23Xt9No=; b=mqoyA/2lbsg4coNSgnM4EjAG79SXTnyZlihW2wqmX1PzcvLeeyq0DCjJTLPmaQn19y VGh3W3mRcc4G2HLm0nmQdr6uNQNr3rspKyor8teQLb6KRMM4582aahBULwVQ30UO6Wd5 MwJ1fxYX7gqpVWpcQVNnm1W5/y8y9IkeyavBbZqDHaiU8qg8AN4yCV9Zu+xtXdc0+yWh wNfCFVXyIEcgG7MvCqcKz4qVy/Yj9NHEqR+I0PjewUdN3cN4Pshh+gu633MsObX29CRE 9wo6/cjJb0gpL/B0aPl81aImbRNCBxvIK1N3ofge6QeMBQmjRoUkKW/kZpjKHiS03JJV oKfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=a/G37s3/UjwAPE/W5DNIRy/pjvBqWVcyDTzt23Xt9No=; b=D3uAhVEMS0rjiyew67uA+dRBC2eUmuN8skCRZNTA+LFWm3jM5Mm4KUzjhlF/xDdKYX KsUZokmJVKfIAtrdOVZxAKyhQUMmDk6oy8LFxXRB5LWZe54JKEFZPk7dwMMKRzYBAfLY jjtcjh1IhROV9IYaFr2jF9mBZeGxfLVV3dwDbnCzPzLK1zAf111o9FibVb09F2F02+r8 JnH/dr37aupDqiEXQc85vyJ8kQ0cXTM0CIbzkgZ1orqhQqIK64v5agH4Gdi0SHiCduSo jRw81+i5WMo5Zm59JUS45acY43u7V0LgSiNQ69mKWfIITpeHzvF3eGmofL6SHeUNDxF4 trDQ== X-Gm-Message-State: AOAM5322j5kFXHFfXvPF9vsGuW+jBEwf0zd/OoZeJnXLcNFKbWz3lZpg rYfNLWiIFCaQVbG32O1vOTM= X-Google-Smtp-Source: ABdhPJy8ziNqMeMIAGWHm6Jef5Dh09mbR/hfx8blme5oiPK5YqEWx6aPza7yu3sEL9EBV+kaB69JTQ== X-Received: by 2002:a17:90a:540f:: with SMTP id z15mr3346326pjh.111.1604596074184; Thu, 05 Nov 2020 09:07:54 -0800 (PST) Received: from google.com ([2620:15c:211:201:7220:84ff:fe09:5e58]) by smtp.gmail.com with ESMTPSA id r8sm2913540pgl.57.2020.11.05.09.07.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2020 09:07:53 -0800 (PST) Sender: Minchan Kim Date: Thu, 5 Nov 2020 09:07:50 -0800 From: Minchan Kim To: Suren Baghdasaryan Cc: Michal Hocko , linux-api@vger.kernel.org, linux-mm , Andrew Morton , David Rientjes , Matthew Wilcox , Johannes Weiner , Roman Gushchin , Rik van Riel , Christian Brauner , Oleg Nesterov , Tim Murray , kernel-team , LKML , Mel Gorman Subject: Re: [RFC]: userspace memory reaping Message-ID: <20201105170750.GA387236@google.com> References: <20201015092030.GB22589@dhcp22.suse.cz> <20201103093550.GE21990@dhcp22.suse.cz> <20201103213228.GB1631979@google.com> <20201104065844.GM21990@dhcp22.suse.cz> <20201104204051.GA3544305@google.com> <20201105122012.GD21348@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu, Nov 05, 2020 at 08:50:58AM -0800, Suren Baghdasaryan wrote: > On Thu, Nov 5, 2020 at 4:20 AM Michal Hocko wrote: > > > > On Wed 04-11-20 12:40:51, Minchan Kim wrote: > > > On Wed, Nov 04, 2020 at 07:58:44AM +0100, Michal Hocko wrote: > > > > On Tue 03-11-20 13:32:28, Minchan Kim wrote: > > > > > On Tue, Nov 03, 2020 at 10:35:50AM +0100, Michal Hocko wrote: > > > > > > On Mon 02-11-20 12:29:24, Suren Baghdasaryan wrote: > > > > > > [...] > > > > > > > To follow up on this. Should I post an RFC implementing SIGKILL_SYNC > > > > > > > which in addition to sending a kill signal would also reap the > > > > > > > victim's mm in the context of the caller? Maybe having some code will > > > > > > > get the discussion moving forward? > > > > > > > > > > > > Yeah, having a code, even preliminary, might help here. This definitely > > > > > > needs a good to go from process management people as that proper is land > > > > > > full of surprises... > > > > > > > > > > Just to remind a idea I suggested to reuse existing concept > > > > > > > > > > fd = pidfd_open(victim process) > > > > > fdatasync(fd); > > > > > close(fd); > > > > > > > > I must have missed this proposal. Anyway, are you suggesting fdatasync > > > > to act as a destructive operation? > > > > > > write(fd) && fdatasync(fd) are already destructive operation if the file > > > is shared. > > > > I am likely missing something because fdatasync will not destroy any > > underlying data. It will sync > > > > > You don't need to reaping as destruptive operation. Rather than, just > > > commit on the asynchrnous status "write file into page cache and commit > > > with fsync" and "killing process and commit with fsync". > > > > I am sorry but I do not follow. The result of the memory reaping is a > > data loss. Any private mapping will simply lose it's content. The caller > > will get EFAULT when trying to access it but there is no way to > > reconstruct the data. This is everything but not resembling what I see > > f{data}sync is used for. > > I think Minchan considers f{data}sync as a "commit" operation. So > write+f{data}sync would mean we write and commit written data, > kill+f{data}sync would mean we kill and commit that kill (reclaim the > resources). If people doesn't like f{data}sync, ftruncate? My point is let's reuse exising API since we have pidfd. What I don't like about SIGKILL_SYNC is that it might introduce several SIGXXX_SYNC later.