Re: [PATCH 1/2] pidmap(2)

On 9/6/17, Randy Dunlap [off-list ref] wrote:

On 09/05/17 15:53, Andrew Morton wrote:

quoted

On Tue, 5 Sep 2017 22:05:00 +0300 Alexey Dobriyan [off-list ref]
wrote:

quoted

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.

also, I expect that the tiny kernel people will want kconfig options for
these syscalls.

We'll add it but the question if it is a good idea. Ideally these system calls
should be mandatory and /proc optional.

$ size kernel/pidmap.o fs/fdmap.o
   text    data     bss     dec     hex filename
    560       0       0     560     230 kernel/pidmap.o
    617       0       0     617     269 fs/fdmap.o