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

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Date:	Thu, 12 Jun 2008 19:35:39 +0300
From:	"Tomas Winkler" <tomasw@...il.com>
To:	"Johannes Berg" <johannes@...solutions.net>
Cc:	"Rik van Riel" <riel@...hat.com>,
	"Zdenek Kabelac" <zdenek.kabelac@...il.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	yi.zhu@...el.com, reinette.chatre@...el.com,
	linux-wireless@...r.kernel.org
Subject: Re: Problem: Out of memory after 2days with 2GB RAM

On Thu, Jun 12, 2008 at 6:43 PM, Tomas Winkler <tomasw@...il.com> wrote:
> On Thu, Jun 12, 2008 at 4:54 PM, Johannes Berg
> <johannes@...solutions.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@...il.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.

So vmalloc  didn't break anything on the 32bit machine I'm just about
to install 64 one so it will take hour or two.. I will issue some
official patch after that.

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

This is  the thread title if you are interested.
'x86/kernel/pci_dma.c: gfp |= __GFP_NORETRY'

Tomas
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