Messages in this thread Patch in this message | | | Date | Mon, 3 Sep 2012 11:08:55 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 1/2] slab: do ClearSlabPfmemalloc() for all pages of slab |
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It took me a while to getting around to reviewing this due to attending kernel summit. Sorry about that.
On Sat, Aug 25, 2012 at 11:11:10PM +0900, Joonsoo Kim wrote: > Now, we just do ClearSlabPfmemalloc() for first page of slab > when we clear SlabPfmemalloc flag. It is a problem because we sometimes > test flag of page which is not first page of slab in __ac_put_obj(). >
Well spotted.
The impact is marginal as far as pfmemalloc protection is concerned. I do not believe that any of the slabs that use high-order allocations are used in for the swap-over-network paths. It would be unfortunate if that ever changed.
> So add code to do ClearSlabPfmemalloc for all pages of slab. >
I would prefer if the pfmemalloc information was kept on the head page. Would the following patch also address your concerns?
diff --git a/mm/slab.c b/mm/slab.c index 811af03..d34a903 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1000,7 +1000,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac, l3 = cachep->nodelists[numa_mem_id()]; if (!list_empty(&l3->slabs_free) && force_refill) { struct slab *slabp = virt_to_slab(objp); - ClearPageSlabPfmemalloc(virt_to_page(slabp->s_mem)); + ClearPageSlabPfmemalloc(virt_to_head_page(slabp->s_mem)); clear_obj_pfmemalloc(&objp); recheck_pfmemalloc_active(cachep, ac); return objp; @@ -1032,7 +1032,7 @@ static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac, { if (unlikely(pfmemalloc_active)) { /* Some pfmemalloc slabs exist, check if this is one */ - struct page *page = virt_to_page(objp); + struct page *page = virt_to_head_page(objp); if (PageSlabPfmemalloc(page)) set_obj_pfmemalloc(&objp); } -- Mel Gorman SUSE Labs
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