Re: Memory overcommit

["Vedran Furač" <vedran.furac@gmail.com>]

Thomas Fjellstrom wrote:

>> malloc: Cannot allocate memory /* Great, no OOM, but: */
>> 
>> % free -m total       used       free     shared    buffers cached
>> Mem:      3458        3429         29          0        102 1119
>> -/+ buffers/cache:    2207       1251
>> 
>> There's plenty of memory available. Shouldn't cache be 
>> automatically dropped (this question was in my original mail, hence
>>  the subject)?
>> 
> 
> I think this is the MOST serious issue related to the oom killer. For
> some reason it refuses to drop pages before trying to kill. When it
> should drop cache, THEN kill if needed.

This isn't about OOM, but situation when you turn off overcommit. I was
jumping to conclusion here. You can drop caches manually with:
# echo 1 > /proc/sys/vm/drop_caches

but you still get: "malloc: Cannot allocate memory" even if almost
nothing is cached:

        total       used       free     shared    buffers     cached
Mem:    3458       2210       1248          0          3          90
-/+ buffers/cache: 2116       1342

As for not dropping pages by kernel before killing, I don't know nothing
about it. It happens so fast and I never tried to measure it.