Fwd: Re: [9fans] Swap considered harmful (Sorry)

[Roderick]

Wow! did you guys know that you could switch off the overcommitment of  
memory?  This posting was recently from the Plan9 o.s. mailing list.   
Thought you all might want this juicy tidbit of Linux hacking info.
Rod
-- 
Roderick Ford, Software Engineer
Open Design Alliance
http://www.opendesign.com/


------- Forwarded message -------
From: "Lluís Batlle i Rossell" <viriketo at gmail.com>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans at cse.psu.edu>
Cc:
Subject: Re: [9fans] Swap considered harmful (Sorry)
Date: Mon, 07 Aug 2006 10:49:05 -0700

Ronald G Minnich wrote:
> Charles Forsyth wrote:
>
>>
>> Linux apparently takes the Atlas approach and thrashes on demand.
>>
>
> until it starts killing random processes. Usually the wrong one. But,
> hey, heuristics, right?

Maybe you already know, but by chance I got into the linux malloc(3)  
manpage, and I found its BUGS section:


BUGS
By default, Linux follows an  optimistic  memory  allocation strategy.  
This  means  that  when malloc() returns non-NULL there is no guarantee  
that the memory really is available. This is a really bad bug. In case it   
turns  out  that the system is out of memory, one or more processes will  
be killed by the infamous OOM killer.  In case Linux  is employed under   
circumstances  where it would be less desirable to suddenly lose some  
randomly picked processes, and moreover the kernel version is sufficiently  
recent, one can switch off this overcommitting behavior using a command  
like
               # echo 2 > /proc/sys/vm/overcommit_memory




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