From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx174.postini.com [74.125.245.174]) by kanga.kvack.org (Postfix) with SMTP id 3C7E96B005D for ; Mon, 3 Sep 2012 06:09:01 -0400 (EDT) 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 Message-ID: <20120903100855.GA11266@suse.de> References: <1345903871-1921-1-git-send-email-js1304@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1345903871-1921-1-git-send-email-js1304@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Pekka Enberg , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Lameter 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 -- 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: email@kvack.org