linux-kernel - Re: [PATCH 1/2] pidmap(2)

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Message-Id: <20170905155320.a683a4853b21a3be32d8b529@linux-foundation.org>
Date:   Tue, 5 Sep 2017 15:53:20 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     Tatsiana Brouka <Tatsiana_Brouka@...m.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Aliaksandr Patseyenak <Aliaksandr_Patseyenak1@...m.com>
Subject: Re: [PATCH 1/2] pidmap(2)

On Tue, 5 Sep 2017 22:05:00 +0300 Alexey Dobriyan <adobriyan@...il.com> wrote:

> Implement system call for bulk retrieveing of pids in binary form.
> 
> Using /proc is slower than necessary: 3 syscalls + another 3 for each thread +
> converting with atoi().
> 
> /proc may be not mounted especially in containers. Natural extension of
> hidepid=2 efforts is to not mount /proc at all.
> 
> It could be used by programs like ps, top or CRIU. Speed increase will
> become more drastic once combined with bulk retrieval of process statistics.

The patches are performance optimizations, but their changelogs contain
no performance measurements!

Demonstration of some compelling real-world performance benefits would
help things along a lot.