Re: [PATCH 1/4] slab: do ClearSlabPfmemalloc() for all pages of slab
From: JoonSoo Kim <hidden>
Date: 2012-09-06 17:57:44
Also in:
linux-mm, lkml
Subsystem:
memory management, the rest · Maintainers:
Andrew Morton, Linus Torvalds
Add "Cc" to "Christoph Lameter" [off-list ref] 2012/9/5 Mel Gorman [off-list ref]:
quoted hunk ↗ jump to hunk
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@gmail.com: Original implementation and problem identification] Signed-off-by: Mel Gorman <mgorman@suse.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.
quoted hunk ↗ jump to hunk
@@ -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);
}
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>