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Sun, 10 Apr 2022 01:12:11 -0700 (PDT) Date: Sun, 10 Apr 2022 17:12:04 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Ohhoon Kwon Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , JaeSang Yoo , Wonhyuk Yang , Jiyoup Kim , Donghyeok Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slub: check pfmemalloc_match in slab_alloc_node fastpath Message-ID: References: <20220409160224.611353-1-ohkwon1043@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220409160224.611353-1-ohkwon1043@gmail.com> X-Rspam-User: X-Stat-Signature: qrc8tuzj6ixjmmoqfh9bf97qazduyuk3 Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=AxDvhhas; spf=pass (imf12.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.216.54 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 74E9740004 X-HE-Tag: 1649578334-269484 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Apr 10, 2022 at 01:02:23AM +0900, Ohhoon Kwon wrote: > If current alloc context does not have __GFP_MEMALLOC in its gfpflags, > then slab objects that were previously created with __GFP_MEMALLOC > should not be given. > > This criteria is well kept in slab alloc slowpath: > When gfpflags does not contain __GFP_MEMALLOC but if per-cpu slab page > was allocated with __GFP_MEMALLOC, then allocator first deactivates > per-cpu slab page and then again allocates new slab page with the > current context's gfpflags. > > However, this criteria is not checked in fastpath. > It should also be checked in the fastpath, too. > > Signed-off-by: Ohhoon Kwon > --- > mm/slub.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 74d92aa4a3a2..c77cd548e106 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3179,7 +3179,8 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, struct list_l > * there is a suitable cpu freelist. > */ > if (IS_ENABLED(CONFIG_PREEMPT_RT) || > - unlikely(!object || !slab || !node_match(slab, node))) { > + unlikely(!object || !slab || !node_match(slab, node) || > + !pfmemalloc_match(slab, gfpflags))) { > object = __slab_alloc(s, gfpflags, node, addr, c); > } else { > void *next_object = get_freepointer_safe(s, object); The missing pfmemalloc check in fastpath was intended. pfmemalloc check in fast did exist in Mel's commit 072bb0aa5e0629 ("mm: sl[au]b: add knowledge of PFMEMALLOC reserve pages"). But later removed by Christoph's commit 5091b74a95d4 ("mm: slub: optimise the SLUB fast path to avoid pfmemalloc checks"). Any thoughts? Thanks! -- Thanks, Hyeonggon