linux-kernel - Re: [RFC 02/18] cgroup_pids: track maximum pids

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Message-ID: <20160613213354.GH31708@htj.duckdns.org>
Date:	Mon, 13 Jun 2016 17:33:54 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Topi Miettinen <toiwoton@...il.com>
Cc:	linux-kernel@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	"open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>
Subject: Re: [RFC 02/18] cgroup_pids: track maximum pids

Hello,

On Mon, Jun 13, 2016 at 09:29:32PM +0000, Topi Miettinen wrote:
> I used fork callback as I don't want to lower the watermark in all cases
> where the charge can be lowered, so I'd update the watermark only when
> the fork really happens.

I don't think that would make a noticeable difference.  That's where
we decide whether to grant fork or not after all and thus where the
actual usage is.

> Is there a better way to compare and set? I don't think atomic_cmpxchg()
> does what's needed,

cmpxchg loop should do what's necessary although I'm not sure how much
being strictly correct matters here.

Thanks.

-- 
tejun