Re: Problem: Out of memory after 2days with 2GB RAM

["Tomas Winkler" <tomasw@gmail.com>]

On Thu, Jun 12, 2008 at 4:54 PM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Thu, 2008-06-12 at 09:38 -0400, Rik van Riel wrote:
>> On Thu, 12 Jun 2008 12:07:34 +0200
>> "Zdenek Kabelac" <zdenek.kabelac@gmail.com> wrote:
>>
>> > It looks like while there was a huge amount of buffers and caches -
>> > system was unable to allocate few pages for kmalloc in iwl3945 driver
>> > after resume.
>>
>> It looks like this is because it wants to allocate 2**5 contiguous
>> pages, which is 128kB of contiguous kernel memory.
>
> 64-bit system I assume?
> The allocation should be 256 * 20 * sizeof(struct sk_buff *).

> Try the patch below. It should improve code generation too.
>
> I discussed this with Tomas previously and he says the hw is capable of
> doing 20 fragments per frame (wonder why, Broadcom can do an unlimited
> number...) but he complained about the networking stack not being able
> to.

This is scatter gather buffers that can be kicked in one DMA transaction.

Well, the hardware needs to support IP checksumming for that, hence,
> afaik, only two fragments can ever be used (one for hw header, one for
> frame)
This I still don't understand why but everybody is already tired to
explaining me why.. :) Just need to find time to dig into it.

> This cuts the allocation to 10%, or (under) a page in all cases.

Probably. it would be safe to use vmalloc for allocating txb anyway.
I'll give it a try.

There was already discussion on LKML about memory allocation problems
on X86_64, which might explain this regression. This didn't happen
before.

Tomas