linux-kernel - Re: [PATCH 02/14] resource limits: aggregate task highwater marks to cgroup level

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Message-ID: <20160718225249.GM3078@mtj.duckdns.org>
Date:	Mon, 18 Jul 2016 18:52:49 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Topi Miettinen <toiwoton@...il.com>
Cc:	linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
	Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Markus Elfring <elfring@...rs.sourceforge.net>,
	"David S. Miller" <davem@...emloft.net>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	"open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>
Subject: Re: [PATCH 02/14] resource limits: aggregate task highwater marks to
 cgroup level

On Fri, Jul 15, 2016 at 05:15:41PM +0000, Topi Miettinen wrote:
> There are clear semantics for the limits themselves, either they apply
> per task or per user. It makes sense to gather values according to these
> semantics. Then with systemd or other tools you can use the valuse to
> set the limits for a service regardless if the limit applies per task or
> per user and it works according to each limit's semantics.

What does it mean to collect the maximum of the high watermarks of
multiple users or the high water marks along process hierarchy which
is spread across multiple cgroups?  These are non-sensical numbers.
If you want to collect high watermarks per-cgroup, the numbers have to
be per-cgroup - how many fds are being used in that particular cgroup
and what's the high watermark of that number and so on.  You can't
just take maximum from process hierarchy or user watermarks.

Thanks.

-- 
tejun