linux-kernel - Re: [RFC PATCH v2 1/3] misc_cgroup: add support for nofile limit

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Message-ID: <YQA1D1GRiF9+px/s@mtj.duckdns.org>
Date:   Tue, 27 Jul 2021 06:32:15 -1000
From:   Tejun Heo <tj@...nel.org>
To:     brookxu <brookxu.cn@...il.com>
Cc:     viro@...iv.linux.org.uk, lizefan.x@...edance.com,
        hannes@...xchg.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/3] misc_cgroup: add support for nofile limit

Hello,

On Tue, Jul 27, 2021 at 11:18:00AM +0800, brookxu wrote:
> According to files_maxfiles_init(), we only allow about 10% of free memory to
> create filps, and each filp occupies about 1K of cache. In this way, on a 16G
> memory machine, the maximum usable filp is about 1,604,644. In general
> scenarios, this may not be a big problem, but if the task is abnormal, it will
> very likely become a bottleneck and affect other modules. 

Yeah but that can be configured trivially through sysfs. The reason why the
default limit is lowered is because we wanna prevent a part of system to
consume all the memory through fds. With cgroups, we already have that
protection and at least some systems already configure file-max to maximum,
so I don't see a point in adding another interface to subdivide the
artificial limit.

Thanks.

-- 
tejun