[RFC] OOM aware applications

[RFC] OOM aware applications

[BALBIR SINGH]

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I was looking at the code in oom_kill.c, I had the following suggestions

Warning: I am not aware of what was discussed earlier about these issues 
or if they were discusses at all.

1. I was wondering that instead of killing the application using 
oom_kill_task() directly, should the OOM
    issue some kind of a warning by sending a signal (some signal with 
si_code set to a value indicating that
    the application is causing memory to run out). Then, wait for a 
while and then see if the application is still
    misbehaving and if so kill it.

2. Minor changes suggested

    In the code, I see

    points *= 2 and points /= 4 in a few places, recommend changing them to

    points <<= 1 and points >>= 2 to help the compiler generate better code


Dialog between the kernel and an OOM aware application

on OOM condition

kernel to the application: Hey u  are running the system out of memory
application: Sorry my lord, I commited a blunder and will rectify myself

application rectifies itself and everybody lives happily everafter
application is stuborn

kernel: You must go now, u have been unfair in your demands and have 
caused a lot of problem
application: Does not get to say anything, it is zapped

Comments, Suggestions, Criticism
Balbir




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Re: [RFC] OOM aware applications

[Matthias Andree]

On Tue, 25 Sep 2001, BALBIR SINGH wrote:

>    In the code, I see
> 
>    points *= 2 and points /= 4 in a few places, recommend changing them to
> 
>    points <<= 1 and points >>= 2 to help the compiler generate better code

Does your compiler really write different code for *= 2 and <<= 1? If
so, try -O :-)

My gcc writes addl %eax,%eax for either case.

-- 
Matthias Andree

"Those who give up essential liberties for temporary safety deserve
neither liberty nor safety." - Benjamin Franklin

Re: [RFC] OOM aware applications

[Andreas Dilger]

On Sep 25, 2001  10:49 +0530, BALBIR SINGH wrote:
> Warning: I am not aware of what was discussed earlier about these issues 
> or if they were discusses at all.

They have been discussed many times.  Please search for SIGDANGER in the
linux-kernel mailing list archive.

> 1. I was wondering that instead of killing the application using 
>    oom_kill_task() directly, should the OOM issue some kind of a
>    warning by sending a signal (some signal with si_code set to a
>    value indicating that the application is causing memory to run
>    out). Then, wait for a while and then see if the application is
>    still misbehaving and if so kill it.

This is exactly what SIGDANGER is.

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert