On 11/29/06, Sonic Zhang <[email protected]> wrote:
Forward to the mailing list.
> On 11/27/06, Nick Piggin <[email protected]> wrote:
>> I haven't actually written any nommu userspace code, but it is obvious
>> that you must try to keep malloc to <= PAGE_SIZE (although order 2 and
>> even 3 allocations seem to be reasonable, from process context)... Then
>> you would use something a bit more advanced than a linear array to store
>> data (a pagetable-like radix tree would be a nice, easy idea).
>>
>
> But, even we split the 8M memory into 2048 x 4k blocks, we still face
> this failure. The key problem is that available memory is small than
> 2048 x 4k, while there are still a lot of VFS cache. The VFS cache can
> be freed, but kernel allocation function ignores it. See the new test
> application.
Which kernel allocation function? If you can provide more details I'd
like to get to the bottom of this.
I posted it here, I think you missed it. So forwarded it to you.
Because the anonymous memory allocation in mm/nommu.c is all allocated
with GFP_KERNEL from process context, and in that case, the allocator
should not fail but call into page reclaim which in turn will free VFS
caches.
> What's a better way to free the VFS cache in memory allocator?
It should be freeing it for you, so I'm not quite sure what is going
on. Can you send over the kernel messages you see when the allocation
fails?
I don't think so. The kernel doesn't attempt to free it. The log is
included in the mail I forwarded to you.
Also, do you happen to know of a reasonable toolchain + emulator setup
that I could test the nommu kernel with?
A project named skyeye.
http://www.skyeye.org/index.shtml
-Aubrey
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