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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 44FBEC33CAF for ; Mon, 13 Jan 2020 19:19:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 052B624670 for ; Mon, 13 Jan 2020 19:19:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="PWAQO6n8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 052B624670 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 906E88E0005; Mon, 13 Jan 2020 14:19:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8DE508E0003; Mon, 13 Jan 2020 14:19:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F3488E0005; Mon, 13 Jan 2020 14:19:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0151.hostedemail.com [216.40.44.151]) by kanga.kvack.org (Postfix) with ESMTP id 6A2A38E0003 for ; Mon, 13 Jan 2020 14:19:02 -0500 (EST) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 2A4F240FB for ; Mon, 13 Jan 2020 19:19:02 +0000 (UTC) X-FDA: 76373573724.01.rice00_14a26d3e9292f X-HE-Tag: rice00_14a26d3e9292f X-Filterd-Recvd-Size: 4123 Received: from mail-ot1-f67.google.com (mail-ot1-f67.google.com [209.85.210.67]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Mon, 13 Jan 2020 19:19:01 +0000 (UTC) Received: by mail-ot1-f67.google.com with SMTP id i15so10067339oto.2 for ; Mon, 13 Jan 2020 11:19:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=NoYTay9gEdUwJzd8flck47gwEsidyqOErVEeC39Jq2o=; b=PWAQO6n8uYq2a4CdtE53n1PqHPbBvA3iHygW7xlF/mSri9aldE4CMUkmnObd7hvGs+ XD3R1Xw11ZzgSnhSmK2jiytZo/UPfvHdS8pHGjOXyjnUpk963f33BYXN60mn6ZimSH7g iiZRP7Sm1suyhXpkmTz0ed2tCy9XjdSobgkM3xuDVIL8GV5mRpPyinERHpcyJgDMCaIn j+f26vKogVX03oygCZPnkb35fMmNiERhbVQNmh0mCoevC5PTlQTz2jgggfS3utSfwGla fT5WYAnROxmU06T+LAPng4nnHMe9Zi4KN5FYNFewShO4WtQI1iD4Zd5FGjZ8i9u1WEvK +kDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=NoYTay9gEdUwJzd8flck47gwEsidyqOErVEeC39Jq2o=; b=jwoYXcO4VJZbffQih+3DGdo/5pYzsP7COGCPGvmHnuz0qoSzz6GEg5BHeboysAVEAQ RtY/YeWix646pk7A3paXzKqZi9EjXYZbscgB9XRK5XJZiyLT27Qa7yenCKxBOJFGZTUw IwbhMZFNnRE8tmf0xrVm17nHfhBeueUoQYkLiGj5XC0HJtN0zS6VsQ90o+/ndCZ4wbKt eAkIicw6794KnCc2ia+yVh+eRmdbPqlHXW9LxLXabfWfse4TPSiKui0HeEvJfuevl1WM 4m6BYJVuSvg8f18gooBmQNudU7NbPdecWJmyUM56gjTVQ2zmNm0YH0c1ClPKM+5dbZSf gxbg== X-Gm-Message-State: APjAAAWWQ7gVzz4PEN3mQg1w1ssJS7k6a3z+Z54vAjlLjqE3RLHHwXWy FV0Oi7X0tjstxCfu1T5znhKu21f50gwKQsNHTpF3Gw== X-Google-Smtp-Source: APXvYqwzd6z4BsjCgwUlGC6h2jl1N7nb469FD4i67Yk4Xbt8zlAhmtvz3QdfKHsOBvBT2VACljpoCk6xfa7vX5xy6N0= X-Received: by 2002:a9d:2028:: with SMTP id n37mr14712535ota.127.1578943140656; Mon, 13 Jan 2020 11:19:00 -0800 (PST) MIME-Version: 1.0 References: <20200110213433.94739-1-minchan@kernel.org> <20200110213433.94739-3-minchan@kernel.org> <56ea0927-ad2e-3fbd-3366-3813330f6cec@virtuozzo.com> In-Reply-To: <56ea0927-ad2e-3fbd-3366-3813330f6cec@virtuozzo.com> From: Daniel Colascione Date: Mon, 13 Jan 2020 11:18:23 -0800 Message-ID: Subject: Re: [PATCH 2/4] mm: introduce external memory hinting API To: Kirill Tkhai Cc: Minchan Kim , Andrew Morton , LKML , linux-mm , Linux API , oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jan 13, 2020, 12:47 AM Kirill Tkhai wrote: > > +SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > > + size_t, len_in, int, behavior, unsigned long, flags) > > I don't like the interface. The fact we have pidfd does not mean, > we have to use it for new syscalls always. A user may want to set > madvise for specific pid from console and pass pid as argument. > pidfd would be an overkill in this case. > We usually call "kill -9 pid" from console. Why shouldn't process_madvise() > allow this? All new APIs should use pidfds: they're better than numeric PIDs in every way. If a program wants to allow users to specify processes by numeric PID, it can parse that numeric PID, open the corresponding pidfd, and then use that pidfd with whatever system call it wants. It's not necessary to support numeric PIDs at the system call level to allow a console program to identify a process by numeric PID.