Re: 2.2/2.4/2.6 VMs: do malloc() ever return NULL?

[Ihar 'Philips' Filipau]

Richard B. Johnson wrote:
> >   May I ask you one question? Did you were ever doing once graceful
> > failure of application under memory pressure? Looks like not.
>
> Yes. I'm in the business of making embedded systems that cannot
> fail. And they do not fail. They allocate memory once during
> startup and they never fail or exit. They also do not use malloc()
> but that's not an issue.

  So what do you use then in user space to reliably allocate memory?

  As to me - memory is a resource. Is it virtual or is it physical - it 
is still resource. And I need to allocate part of this resource.

  malloc() uses brk() inside. But brk() is "implementation details". I 
honestly do not care about them - I just want to be sure that what ever 
resource I have allocated - I can use it afterwards until I shall free 
it. POSIX even doesn't mention brk() BTW.

  If you can hint me any other method to allocate memory without 
surprises - I will really appreciate.

> >   Memory pools used by applications exactly to make grace error
> > handling under memory pressure - but it looks like this stuff under
> > Linux gets no testing at all. And default settings could make from
> > simple bug complete disaster.
>
> Wrong. It is up to the application to allocate and deallocate
> dynamic memory properly.  FYI, you can always look at /proc/meminfo
> yourself instead of expecting malloc() to do it for you. You only
> need to look at swap.

  Embedded? with swap?!?
  What you have smoken?! - take me to your dealer!-)))

  And btw Rik already gave me answer - 2.6 kernels + 
/proc/sys/vm/overcommit_memory == 2.
  Work charmfully ;-)
  Enjoy.

--
Ihar 'Philips' Filipau  / with best regards from Saarbruecken.
--                                                           _ _ _
 Because the kernel depends on it existing. "init"          |_|*|_|
 literally _is_ special from a kernel standpoint,           |_|_|*|
 because its' the "reaper of zombies" (and, may I add,      |*|*|*|
 that would be a great name for a rock band).
                                -- Linus Torvalds

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