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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 D0647C432C3 for ; Thu, 14 Nov 2019 10:23:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3C73206F0 for ; Thu, 14 Nov 2019 10:23:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726923AbfKNKX5 (ORCPT ); Thu, 14 Nov 2019 05:23:57 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:34861 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726473AbfKNKX5 (ORCPT ); Thu, 14 Nov 2019 05:23:57 -0500 Received: from [79.140.120.64] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1iVCI0-0004Z2-Iy; Thu, 14 Nov 2019 10:23:48 +0000 Date: Thu, 14 Nov 2019 11:23:47 +0100 From: Christian Brauner To: Arnd Bergmann Cc: Cyrill Gorcunov , y2038 Mailman List , Richard Henderson , Ivan Kokshaysky , Matt Turner , "linux-kernel@vger.kernel.org" , Deepa Dinamani , Thomas Gleixner , Will Deacon , Michal =?utf-8?Q?Koutn=C3=BD?= , Catalin Marinas , Dave Hansen , alpha , fweimer@redhat.com, libc-alpha@sourceware.org Subject: Re: [PATCH 11/23] y2038: rusage: use __kernel_old_timeval Message-ID: <20191114102346.bjwsz2iup7pg7mgd@wittgenstein> References: <20191108210236.1296047-1-arnd@arndb.de> <20191108211323.1806194-2-arnd@arndb.de> <20191112210915.GD5130@uranus> <20191114003822.6fjji26vm7yplaw2@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [+Cc Florian, libc-alpha] On Thu, Nov 14, 2019 at 11:18:15AM +0100, Arnd Bergmann wrote: > On Thu, Nov 14, 2019 at 1:38 AM Christian Brauner > wrote: > > On Wed, Nov 13, 2019 at 11:02:12AM +0100, Arnd Bergmann wrote: > > > On Tue, Nov 12, 2019 at 10:09 PM Cyrill Gorcunov wrote: > > > > > > > > On Fri, Nov 08, 2019 at 10:12:10PM +0100, Arnd Bergmann wrote: > > > > > > > > --- > > > > > Question: should we also rename 'struct rusage' into 'struct __kernel_rusage' > > > > > here, to make them completely unambiguous? > > > > > > > > The patch looks ok to me. I must confess I looked into rusage long ago > > > > so __kernel_timespec type used in uapi made me nervious at first, > > > > but then i found that we've this type defined in time_types.h uapi > > > > so userspace should be safe. I also like the idea of __kernel_rusage > > > > but definitely on top of the series. > > > > > > There are clearly too many time types at the moment, but I'm in the > > > process of throwing out the ones we no longer need now. > > > > > > I do have a number patches implementing other variants for the syscall, > > > and I suppose that if we end up adding __kernel_rusage, that would > > > have to go with a set of syscalls using 64-bit seconds/nanoseconds > > > rather than the old 32/64 microseconds. I don't know what other > > > changes remain that anyone would want from sys_waitid() now that > > > it does support pidfd. > > > > > > If there is still a need for a new waitid() replacement, that should take > > > that new __kernel_rusage I think, but until then I hope we are fine > > > with today's getrusage+waitid based on the current struct rusage. > > > > Note, that glibc does _not_ expose the rusage argument, i.e. most of > > userspace is unaware that waitid() does allow you to get rusage > > information. So users first need to know that waitid() has an rusage > > argument and then need to call the waitid() syscall directly. > > On architectures that don't have a wait4 syscall (riscv32 for now), > glibc uses waitid to implement wait4 and wait3. Yes, and there's an ongoing discussion to implement wait4() on all arches through waitid(), I think. I haven't followed it too closely. > > > > BSD has wait6() to return separate rusage structures for 'self' and > > > 'children', but I could not find any application (using the freebsd > > > sources and debian code search) that actually uses that information, > > > so there might not be any demand for that. > > > > Speaking specifically for Linux now, I think that rusage does not > > actually expose the information most relevant users are interested in. > > On Linux nowadays it is _way_ more interesting to retrieve stats > > relative to the cgroup the task lived in etc. > > Doing a git grep -i rusage in the systemd source code shows that rusage > > is used _nowhere_. And I consider an init system to be the most likely > > candidate to be interested in rusage. > > I looked at a couple of implementations of time(1), this is one example > that sometimes uses wait3(), though other implementations just call > getrusage() in the parent process before the fork/exec. None of them > actually seem to report better than millisecond resolution, so there is > not a strict reason to do a timespec replacement for these. Right, though I have to say that for the sake of consistency I'd much rather have a replacement. We're doing all this work right now so we might as well. But I get the point. Christian