lkml.org 
[lkml]   [2011]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] ipc: introduce shm_rmid_forced sysctl

* Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> > As we really prefer working systems over non-working ones (and lots
> > of unattached shm segments can clearly result in a non-working
> > system) we can only accept the "this will break stuff" argument if
> > it's *demonstrated* to break stuff and if the failure scenario is
> > carefully described in the commit.
> >
> > It would take a serious breakage to override a "system locks up
> > swapping itself to death" failure scenario.
>
> Ths shared memory interface is defined to be persistent for good
> reason and all sorts of apps rely upon that so no you can't just
> ignore that. As a configurable alternative it makes sense (indeed
> many SYS5 admins used to run shared memory segment sweepers to
> clean up long idle ones)
>
> However if it's locking the machine up and not being properly
> handled by resource management then
>
> a) your resource management is broken so fix that instead
> b) if your resource management is busted or you are not properly
> tracking resource commits then the user is going to be able to achieve the
> same result by other means (eg a unix domain socket bomb)
>
> If you've got no overcommit set you shouldn't be able to swap to
> death, it may be the sysv shared memory objects need to be
> accounted for specifically somewhere but that would be the right
> thing to fix and the mechanisms to do it exist.

But the majority of systems have overcommit enabled - that is our
default.

This is a simple extension of the OOM killer being able to ... kill
things on OOM, ok? 'to kill' implies 'to break'.

Thanks,

Ingo


\
 
 \ /
  Last update: 2011-07-03 21:41    [W:0.048 / U:47.952 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site