linux-kernel - Re: [PATCH 00/14] Present useful limits to user (v2)

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Date:	Fri, 15 Jul 2016 13:54:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Topi Miettinen <toiwoton@...il.com>
CC:	linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Alexander Graf <agraf@...e.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Radim Kr??m???? <rkrcmar@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
	Doug Ledford <dledford@...hat.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Mike Marciniszyn <mike.marciniszyn@...el.com>,
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	Alex Williamson <alex.williamson@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Tejun Heo <tj@...nel.org>, Li.Zefan@...or.com
Subject: Re: [PATCH 00/14] Present useful limits to user (v2)

<lizefan@...wei.com>,Johannes Weiner <hannes@...xchg.org>,Alexei Starovoitov <ast@...nel.org>,Arnaldo Carvalho de Melo <acme@...nel.org>,Alexander Shishkin <alexander.shishkin@...ux.intel.com>,Balbir Singh <bsingharora@...il.com>,Markus Elfring <elfring@...rs.sourceforge.net>,"David S. Miller" <davem@...emloft.net>,Nicolas Dichtel <nicolas.dichtel@...nd.com>,Andrew Morton <akpm@...ux-foundation.org>,Konstantin Khlebnikov <koct9i@...il.com>,Jiri Slaby <jslaby@...e.cz>,Cyrill Gorcunov <gorcunov@...nvz.org>,Michal Hocko <mhocko@...e.com>,Vlastimil Babka <vbabka@...e.cz>,Dave Hansen <dave.hansen@...ux.intel.com>,Greg Kroah-Hartman <gregkh@...uxfoundation.org>,Dan Carpenter <dan.carpenter@...cle.com>,Michael Kerrisk <mtk.manpages@...il.com>,"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,Marcus Gelderie <redmnic@...il.com>,Vladimir Davydov <vdavydov@...tuozzo.com>,Joe Perches <joe@...ches.com>,Frederic Weisbecker <fweisbec@...il.com>,Andrea Arcangeli <aarcange@...hat.com>,!
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Biederman" <ebiederm@...ssion.com>,Andi Kleen <ak@...ux.intel.com>,Oleg Nesterov <oleg@...hat.com>,Stas Sergeev <stsp@...t.ru>,Amanieu d'Antras <amanieu@...il.com>,Richard Weinberger <richard@....at>,Wang Xiaoqiang <wangxq10@....edu.cn>,Helge Deller <deller@....de>,Mateusz Guzik <mguzik@...hat.com>,Alex Thorlton <athorlton@....com>,Ben Segall <bsegall@...gle.com>,John Stultz <john.stultz@...aro.org>,Rik van Riel <riel@...hat.com>,Eric B Munson <emunson@...mai.com>,Alexey Klimov <klimov.linux@...il.com>,Chen Gang <gang.chen.5i5j@...il.com>,Andrey Ryabinin <aryabinin@...tuozzo.com>,David Rientjes <rientjes@...gle.com>,Hugh Dickins <hughd@...gle.com>,Alexander Kuleshov <kuleshovmail@...il.com>,"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,"open list:IA64 (Itanium) PLATFORM" <linux-ia64@...r.kernel.org>,"open list:KERNEL VIRTUAL MACHINE (KVM) FOR POWERPC" <kvm-ppc@...r.kernel.org>,"open list:KERNEL VIRTUAL MACHINE (KVM)" <kvm@...r.kernel.org>,"open list:LINUX FOR POWERPC!
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Message-ID: <D79806FE-E6B9-481B-8AA2-A1800419D9B5@...or.com>

On July 15, 2016 6:59:56 AM PDT, Peter Zijlstra <peterz@...radead.org> wrote:
>On Fri, Jul 15, 2016 at 01:52:48PM +0000, Topi Miettinen wrote:
>> On 07/15/16 12:43, Peter Zijlstra wrote:
>> > On Fri, Jul 15, 2016 at 01:35:47PM +0300, Topi Miettinen wrote:
>> >> Hello,
>> >>
>> >> There are many basic ways to control processes, including
>capabilities,
>> >> cgroups and resource limits. However, there are far fewer ways to
>find out
>> >> useful values for the limits, except blind trial and error.
>> >>
>> >> This patch series attempts to fix that by giving at least a nice
>starting
>> >> point from the highwater mark values of the resources in question.
>> >> I looked where each limit is checked and added a call to update
>the mark
>> >> nearby.
>> > 
>> > And how is that useful? Setting things to the high watermark is
>> > basically the same as not setting the limit at all.
>> 
>> What else would you use, too small limits?
>
>That question doesn't make sense.
>
>What's the point of setting a limit if it ends up being the same as
>no-limit (aka unlimited).
>
>If you cannot explain; and you have not so far; what use these values
>are, why would we look at the patches.

One reason is to catch a malfunctioning process rather than dragging the whole system down with it.  It could also be useful for development.
-- 
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