Re: alloc_pages_node(... GFP_KERNEL | GFP_THISNODE ...) fails

["Max Laier" <max@laiers.net>]

Am Fr, 29.05.2009, 20:26, schrieb Andi Kleen:
>> No, the test module is fine.  The exact same call in the KVM allocation
>> routine, however, does not work.  Again, please see my initial post.
>
> Sorry I don't have time to reverse engineer/debug your patches.
>
> If you can't state the problem clearly there's probably no way
> other people can help you on the mailing list.

I'm sorry if I sounded snippy, this wasn't intended.  I hope I haven't
pissed away your good will yet - which is indeed greatly appreciated.  So
let me try again to be more precise in specifying my problem:

I'm trying to replace a call to alloc_page() with alloc_pages_node() in
order to membind the allocation to a specific node set.  This seemed to
work - as page_to_nid() returns the selected node.  However, the free
memory in that node isn't decreasing.

I tried to build a test module to recreate the problem, but the test
module doesn't exhibit the bug.  I assume that is because there is
something different with the context from which the allocation is
happening.  I tried to follow the code path of alloc_pages_node() to find
out what that difference might be, but didn't succeed.  Hence I attached a
boiled down version of my changes that still demonstrate the problem. 
It's really a one line change in kvm.

I was hoping that someone with real numa hardware and kvm capabilities
would be able to test this tiny patch in order to find out if the problem
lies with the fake numa or indeed the context of the allocation so I could
focus my efforts on the right target.

Alternatively, I'd also be greatful if anybody had any idea why
alloc_pages_node() would behave differently in different context and what
that difference would be.

Again, sorry if I sounded ungreatful.  I do appreciate any help or
pointers you could give me.  I don't expect a final sollution and am
willing and ready to invest more time of my own to fixing this.  I just
need some idea in which direction to go:  fake numa or context.

Thanks.

-- 
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