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Groups > linux.kernel > #1236758 > unrolled thread

[RFC 0/4] reduce pid_namespace footprint when not configured

Started byRasmus Villemoes <linux@rasmusvillemoes.dk>
First post2015-09-30 23:00 +0200
Last post2015-09-30 23:40 +0200
Articles 3 — 2 participants

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  [RFC 0/4] reduce pid_namespace footprint when not configured Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-09-30 23:00 +0200
    Re: [RFC 0/4] reduce pid_namespace footprint when not configured ebiederm@xmission.com (Eric W. Biederman) - 2015-09-30 23:20 +0200
      Re: [RFC 0/4] reduce pid_namespace footprint when not configured Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-09-30 23:40 +0200

#1236758 — [RFC 0/4] reduce pid_namespace footprint when not configured

FromRasmus Villemoes <linux@rasmusvillemoes.dk>
Date2015-09-30 23:00 +0200
Subject[RFC 0/4] reduce pid_namespace footprint when not configured
Message-ID<qewDL-7OB-5@gated-at.bofh.it>
A few suggestions for reducing the footprint of pid namespaces when
CONFIG_PID_NS=n. The savings are admittedly not huge:

$ scripts/bloat-o-meter /tmp/vmlinux.master vmlinux
add/remove: 0/7 grow/shrink: 30/25 up/down: 368/-1032 (-664)

Rasmus Villemoes (4):
  pid_namespace: remove ->level and ->parent for !CONFIG_PID_NS
  pid_namespace: remove .kref field for !CONFIG_PID_NS
  pid_namespace: make pid_nr_ns and pid_vnr static inlines for
    !CONFIG_PID_NS
  pid_namespace: disable_pid_allocation is unused for !CONFIG_PID_NS

 include/linux/pid.h           | 11 +++++++++++
 include/linux/pid_namespace.h | 20 ++++++++++++++++++++
 kernel/acct.c                 |  4 ++--
 kernel/pid.c                  | 24 +++++++++++++++---------
 4 files changed, 48 insertions(+), 11 deletions(-)

-- 
2.1.3

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#1236769

Fromebiederm@xmission.com (Eric W. Biederman)
Date2015-09-30 23:20 +0200
Message-ID<qewX8-8qQ-19@gated-at.bofh.it>
In reply to#1236758
Rasmus Villemoes <linux@rasmusvillemoes.dk> writes:

> A few suggestions for reducing the footprint of pid namespaces when
> CONFIG_PID_NS=n. The savings are admittedly not huge:
>
> $ scripts/bloat-o-meter /tmp/vmlinux.master vmlinux
> add/remove: 0/7 grow/shrink: 30/25 up/down: 368/-1032 (-664)

#ifdefs in C files.
More code to maintain.
Very minor savings.

I don't think it is worth the pain.  If anything I would prefer to
remove CONFIG_PID_NS.  The CONFIG_PID_NS ifdef really is about keeping
from exposing people to the feature tha don't use it more than it is
about size reduction.

Or do you have a case where this makes the difference between a usable
kernel and a kernel that is not?

Eric


> Rasmus Villemoes (4):
>   pid_namespace: remove ->level and ->parent for !CONFIG_PID_NS
>   pid_namespace: remove .kref field for !CONFIG_PID_NS
>   pid_namespace: make pid_nr_ns and pid_vnr static inlines for
>     !CONFIG_PID_NS
>   pid_namespace: disable_pid_allocation is unused for !CONFIG_PID_NS
>
>  include/linux/pid.h           | 11 +++++++++++
>  include/linux/pid_namespace.h | 20 ++++++++++++++++++++
>  kernel/acct.c                 |  4 ++--
>  kernel/pid.c                  | 24 +++++++++++++++---------
>  4 files changed, 48 insertions(+), 11 deletions(-)
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#1236780

FromRasmus Villemoes <linux@rasmusvillemoes.dk>
Date2015-09-30 23:40 +0200
Message-ID<qexgt-oR-9@gated-at.bofh.it>
In reply to#1236769
On Wed, Sep 30 2015, ebiederm@xmission.com (Eric W. Biederman) wrote:

> Rasmus Villemoes <linux@rasmusvillemoes.dk> writes:
>
>> A few suggestions for reducing the footprint of pid namespaces when
>> CONFIG_PID_NS=n. The savings are admittedly not huge:
>>
>> $ scripts/bloat-o-meter /tmp/vmlinux.master vmlinux
>> add/remove: 0/7 grow/shrink: 30/25 up/down: 368/-1032 (-664)
>
> #ifdefs in C files.
> More code to maintain.
> Very minor savings.
>
> I don't think it is worth the pain.  If anything I would prefer to
> remove CONFIG_PID_NS.  The CONFIG_PID_NS ifdef really is about keeping
> from exposing people to the feature tha don't use it more than it is
> about size reduction.
>
> Or do you have a case where this makes the difference between a usable
> kernel and a kernel that is not?

No, it was mostly a small tinification effort, and we'd presumably also
save a few cycles on thread creation, but not anything measurable.

Rasmus

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