Re: [PATCH v2] tmpfs not interleaving properly
From: KOSAKI Motohiro
Date: Fri Jun 01 2012 - 13:22:16 EST
(6/1/12 10:24 AM), Nathan Zimmer wrote:
On Thu, May 31, 2012 at 04:35:53PM -0400, KOSAKI Motohiro wrote:
(5/31/12 4:25 PM), Andrew Morton wrote:
On Thu, 31 May 2012 16:09:15 -0400
KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxx> wrote:
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -929,7 +929,7 @@ static struct page *shmem_alloc_page(gfp_t gfp,
/*
* alloc_page_vma() will drop the shared policy reference
*/
- return alloc_page_vma(gfp,&pvma, 0);
+ return alloc_page_vma(gfp,&pvma, info->node_offset<< PAGE_SHIFT );
3rd argument of alloc_page_vma() is an address. This is type error.
Well, it's an unsigned long...
But yes, it is conceptually wrong and *looks* weird. I think we can
address that by overcoming our peculair aversion to documenting our
code, sigh. This?
Sorry, no.
addr agrument of alloc_pages_vma() have two meanings.
1) interleave node seed
2) look-up key of shmem policy
I think this patch break (2). shmem_get_policy(pol, addr) assume caller honor to
pass correct address.
But the pseudo vma we generated in shmem_alloc_page the vm_ops are set to NULL.
So get_vma_policy will return the policy provided by the pseudo vma and not reach
the shmem_get_policy.
yes, and it is bug source. we may need to change soon. I guess the right way is
to make vm_ops->interleave and interleave_nid uses it if povided.
btw, I don't think node_random() is good idea. it is random(pid + jiffies + cycle).
current->cpuset_mem_spread_rotor is per-thread value. but you now need per-inode
interleave offset. maybe, just inode addition is enough. Why do you need randomness?
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