Problem with OOM killer killing process even when there is plenty of RAM.

[Rajat Sharma]

On Thu, Dec 8, 2011 at 1:41 AM, Greg KH <greg at kroah.com> wrote:
> On Thu, Dec 08, 2011 at 01:26:42AM +0530, mindentropy wrote:
>> On Wednesday 07 Dec 2011 11:35:36 AM Greg KH wrote:
>> > On Thu, Dec 08, 2011 at 12:36:43AM +0530, mindentropy wrote:
>> > > On Thursday 08 Dec 2011 1:38:19 AM Mulyadi Santosa wrote:
>> > > > On Wed, Dec 7, 2011 at 01:47, mindentropy <mindentropy at gmail.com> wrote:
>> > > > > Hi,
>> > > > >
>> > > > >  I am trying to allocate 512MB of RAM in my driver loaded as a
>> > > > >  module,> > >
>> > > > > but the OOM killer starts killing all my processes. This machine
>> > > > > has
>> > > > > around 24GB RAM and is a 8 core Xeon. The RAM is allocated in
>> > > > > page size chunks (i.e. 131072 chunks each of size PAGE_SIZE).
>> > > >
>> > > > mind to tell us, how do you allocate memory? kmalloc?
>> > >
>> > > Via kmalloc.
>> >
>> > Please use the functions written to give you large memory chunks.  As
>> > you are using a video-for-linux device, why not use the apis that this
>> > framework provides you for this type of thing?
>> >
>>
>> Yes V4L would be done next. There are some things being tried out, this being
>> a custom FPGA hence some controls being experimented.
>>
>> As for the allocating in PAGE_SIZE chunks why am I running out of memory?
>
> The kernel doesn't like allocating such large sizes all at once.
>
>> Can't it steal smaller chunks from the larger chunks? Just curious about the
>> reason.
>
> Use vmalloc if you need/want larger chunks, kmalloc is not for that at
> all.
>
> greg k-h
>
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Probably if it is some custom hardware, and you can afford to allocate
memory at boot time, then reserve it exclusively for your use only.

-Rajat