linux-kernel - Re: [PATCH] ipv4: Namespaceify tcp_max

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Date:   Sat, 9 Sep 2017 13:09:57 +0800
From:   严海双 <yanhaishuang@...s.chinamobile.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ipv4: Namespaceify tcp_max_orphans knob



> On 2017年9月9日, at 下午12:35, Cong Wang <xiyou.wangcong@...il.com> wrote:
> 
> On Fri, Sep 8, 2017 at 6:25 PM, 严海双 <yanhaishuang@...s.chinamobile.com> wrote:
>> 
>> 
>>> On 2017年9月9日, at 上午6:13, Cong Wang <xiyou.wangcong@...il.com> wrote:
>>> 
>>> On Wed, Sep 6, 2017 at 8:10 PM, Haishuang Yan
>>> <yanhaishuang@...s.chinamobile.com> wrote:
>>>> Different namespace application might require different maximal number
>>>> of TCP sockets independently of the host.
>>> 
>>> So after your patch we could have N * net->ipv4.sysctl_tcp_max_orphans
>>> in a whole system, right? This just makes OOM easier to trigger.
>>> 
>> 
>> From my understanding, before the patch, we had N * net->ipv4.sysctl_tcp_max_orphans,
>> and after the patch, we could have ns1.sysctl_tcp_max_orphans + ns2.sysctl_tcp_max_orphans
>> + ns3.sysctl_tcp_max_orphans, is that right? Thanks for your reviewing.
> 
> Nope, by N I mean the number of containers. Before your patch, the limit
> is global, after your patch it is per container.
> 

Yeah, for example, if there is N containers, before the patch, I mean the limit is:

	N * net->ipv4.sysctl_tcp_max_orphans

After the patch, the limit is:

	ns1. net->ipv4.sysctl_tcp_max_orphans + ns2. net->ipv4.sysctl_tcp_max_orphans + …