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Message-ID: <CAAmzW4MfFUH1Mi447sQvPNeae_BShEmbECUaK9eoX-8ughEdJw@mail.gmail.com>
Date: Fri, 7 Sep 2012 03:05:39 +0900
From: JoonSoo Kim <js1304@...il.com>
To: Mel Gorman <mgorman@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>,
Linux-Netdev <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
David Miller <davem@...emloft.net>,
Chuck Lever <chuck.lever@...cle.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH 1/4] slab: do ClearSlabPfmemalloc() for all pages of slab
Correct Pekka's mail address and resend.
Sorry.
Add "Cc" to "Christoph Lameter" <cl@...ux.com>
2012/9/5 Mel Gorman <mgorman@...e.de>:
> Right now, we call ClearSlabPfmemalloc() for first page of slab when we
> clear SlabPfmemalloc flag. This is fine for most swap-over-network use
> cases as it is expected that order-0 pages are in use. Unfortunately it
> is possible that that __ac_put_obj() checks SlabPfmemalloc on a tail page
> and while this is harmless, it is sloppy. This patch ensures that the head
> page is always used.
>
> This problem was originally identified by Joonsoo Kim.
>
> [js1304@...il.com: Original implementation and problem identification]
> Signed-off-by: Mel Gorman <mgorman@...e.de>
> ---
> mm/slab.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> 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;
We assume that slabp->s_mem's address is always in head page, so
"virt_to_head_page" is not needed.
> @@ -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);
> }
> --
> 1.7.9.2
>
If we always use head page, following suggestion is more good to me.
How about you?
diff --git a/mm/slab.c b/mm/slab.c
index f8b0d53..ce70989 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -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);
}
@@ -1921,10 +1921,9 @@ static void *kmem_getpages(struct kmem_cache
*cachep, gfp_t flags, int nodeid)
NR_SLAB_UNRECLAIMABLE, nr_pages);
for (i = 0; i < nr_pages; i++) {
__SetPageSlab(page + i);
-
- if (page->pfmemalloc)
- SetPageSlabPfmemalloc(page + i);
}
+ if (page->pfmemalloc)
+ SetPageSlabPfmemalloc(page);
if (kmemcheck_enabled && !(cachep->flags & SLAB_NOTRACK)) {
kmemcheck_alloc_shadow(page, cachep->gfporder, flags, nodeid);
@@ -1943,26 +1942,26 @@ static void *kmem_getpages(struct kmem_cache
*cachep, gfp_t flags, int nodeid)
*/
static void kmem_freepages(struct kmem_cache *cachep, void *addr)
{
- unsigned long i = (1 << cachep->gfporder);
+ int nr_pages = (1 << cachep->gfporder);
+ int i;
struct page *page = virt_to_page(addr);
- const unsigned long nr_freed = i;
kmemcheck_free_shadow(page, cachep->gfporder);
if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
sub_zone_page_state(page_zone(page),
- NR_SLAB_RECLAIMABLE, nr_freed);
+ NR_SLAB_RECLAIMABLE, nr_pages);
else
sub_zone_page_state(page_zone(page),
- NR_SLAB_UNRECLAIMABLE, nr_freed);
- while (i--) {
- BUG_ON(!PageSlab(page));
- __ClearPageSlabPfmemalloc(page);
- __ClearPageSlab(page);
- page++;
+ NR_SLAB_UNRECLAIMABLE, nr_pages);
+ for (i = 0; i < nr_pages; i++) {
+ BUG_ON(!PageSlab(page + i));
+ __ClearPageSlab(page + i);
}
+ __ClearPageSlabPfmemalloc(page);
+
if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab += nr_freed;
+ current->reclaim_state->reclaimed_slab += nr_pages;
free_pages((unsigned long)addr, cachep->gfporder);
}
--
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