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SubjectRe: __GFP flags and kmalloc failures
Marcelo Tosatti wrote:

>On Tue, Nov 02, 2004 at 04:49:20PM +0100, Pierre Ossman wrote:
>
>
>>
>>The problem is now that this allocation doesn't always succeed. When it
>>fails I get:
>>
>>insmod: page allocation failure. order:4, mode:0x11
>>
>>
>
>This is a big allocation and the kernel is having problem finding such a
>big page, due to memory fragmentation (as you mention below).
>
>What kernel version are you using?
>
>
I'm currently running 2.6.9. No external patches (except for my own
stuff related to this driver).

>-mm contains a series of patches from Nick which should make the situation
>better, have you tried it? Currently kswapd doenst honour high order
>page shortage.
>
>
>
No I haven't. Only saw it today and I usually don't use the -mm tree.
I've gotten the impression it's a bit too bleeding edge for me ;)
What do these patches add to the mix?
I'm also not familiar what the order means. I guess it's some kind of
priority system? Is there a way I can raise my priority to get access to
the memory that kswapd actually keeps available?

>>As for solutions I've tried using __GFP_REPEAT which seems to do the
>>trick. But the double underscore indicates (at least to me) that these
>>are internal defines that shouldn't be used except for very special
>>cases. What is the policy about these?
>>
>>
>
>Its OK to use these flags externally. They might change in future major kernel
>versions though, or even future v2.6 release. ie its not a stable API.
>
>
Is there any other way of increasing the chances of actually getting the
pages I need? Since it is DMA it needs to be one big block.

Rgds
Pierre
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