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[90.235.0.207]) by smtp.gmail.com with ESMTPSA id v25-20020ac25619000000b0048a982ad0a8sm1704357lfd.23.2023.03.06.08.37.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Mar 2023 08:37:04 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 6 Mar 2023 17:37:02 +0100 To: Michal Hocko Cc: Uladzislau Rezki , Gao Xiang , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , Vlastimil Babka , Baoquan He , Christoph Hellwig Subject: Re: [PATCH] mm, vmalloc: fix high order __GFP_NOFAIL allocations Message-ID: References: <20230305053035.1911-1-hsiangkao@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6E848A001E X-Stat-Signature: gecaby7oj9idcg6uhsaa3q4k7fb9ddh3 X-HE-Tag: 1678120627-915432 X-HE-Meta: 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 5M2wCp/s 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 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 Mon, Mar 06, 2023 at 03:03:10PM +0100, Michal Hocko wrote: > On Mon 06-03-23 13:14:43, Uladzislau Rezki wrote: > [...] > > Some questions: > > > > 1. Could you please add a comment why you want the bulk_gfp without > > the __GFP_NOFAIL(bulk path)? > > The bulk allocator is not documented to fully support __GFP_NOFAIL > semantic IIRC. While it uses alloc_pages as fallback I didn't want > to make any assumptions based on the current implementation. At least > that is my recollection. If we do want to support NOFAIL by the batch > allocator then we can drop the special casing here. > > > 2. Could you please add a comment why a high order pages do not want > > __GFP_NOFAIL? You have already explained. > > See below > > 3. Looking at the patch: > > > > > > + } else { > > + alloc_gfp &= ~__GFP_NOFAIL; > > + nofail = true; > > > > > > if user does not want to go with __GFP_NOFAIL flag why you force it in > > case a high order allocation fails and you switch to 0 order allocations? > > Not intended. The above should have been else if (gfp & __GFP_NOFAIL). > Thanks for catching that! > > This would be the full patch with the description: > --- > From 3ccfaa15bf2587b8998c129533a0404fedf5a484 Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Mon, 6 Mar 2023 09:15:17 +0100 > Subject: [PATCH] mm, vmalloc: fix high order __GFP_NOFAIL allocations > > Gao Xiang has reported that the page allocator complains about high > order __GFP_NOFAIL request coming from the vmalloc core: > > __alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5549 > alloc_pages+0x1aa/0x270 mm/mempolicy.c:2286 > vm_area_alloc_pages mm/vmalloc.c:2989 [inline] > __vmalloc_area_node mm/vmalloc.c:3057 [inline] > __vmalloc_node_range+0x978/0x13c0 mm/vmalloc.c:3227 > kvmalloc_node+0x156/0x1a0 mm/util.c:606 > kvmalloc include/linux/slab.h:737 [inline] > kvmalloc_array include/linux/slab.h:755 [inline] > kvcalloc include/linux/slab.h:760 [inline] > > it seems that I have completely missed high order allocation backing > vmalloc areas case when implementing __GFP_NOFAIL support. This means > that [k]vmalloc at al. can allocate higher order allocations with > __GFP_NOFAIL which can trigger OOM killer for non-costly orders easily > or cause a lot of reclaim/compaction activity if those requests cannot > be satisfied. > > Fix the issue by falling back to zero order allocations for __GFP_NOFAIL > requests if the high order request fails. > > Fixes: 9376130c390a ("mm/vmalloc: add support for __GFP_NOFAIL") > Reported-by: Gao Xiang > Signed-off-by: Michal Hocko > --- > mm/vmalloc.c | 28 +++++++++++++++++++++++----- > 1 file changed, 23 insertions(+), 5 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index ef910bf349e1..bef6cf2b4d46 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2883,6 +2883,8 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > unsigned int order, unsigned int nr_pages, struct page **pages) > { > unsigned int nr_allocated = 0; > + gfp_t alloc_gfp = gfp; > + bool nofail = false; > struct page *page; > int i; > > @@ -2893,6 +2895,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > * more permissive. > */ > if (!order) { > + /* bulk allocator doesn't support nofail req. officially */ > gfp_t bulk_gfp = gfp & ~__GFP_NOFAIL; > > while (nr_allocated < nr_pages) { > @@ -2931,20 +2934,35 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > if (nr != nr_pages_request) > break; > } > + } else if (gfp & __GFP_NOFAIL) { > + /* > + * Higher order nofail allocations are really expensive and > + * potentially dangerous (pre-mature OOM, disruptive reclaim > + * and compaction etc. > + */ > + alloc_gfp &= ~__GFP_NOFAIL; > + nofail = true; > } > > /* High-order pages or fallback path if "bulk" fails. */ > - > while (nr_allocated < nr_pages) { > if (fatal_signal_pending(current)) > break; > > if (nid == NUMA_NO_NODE) > - page = alloc_pages(gfp, order); > + page = alloc_pages(alloc_gfp, order); > else > - page = alloc_pages_node(nid, gfp, order); > - if (unlikely(!page)) > - break; > + page = alloc_pages_node(nid, alloc_gfp, order); > + if (unlikely(!page)) { > + if (!nofail) > + break; > + > + /* fall back to the zero order allocations */ > + alloc_gfp |= __GFP_NOFAIL; > + order = 0; > + continue; > + } > + > /* > * Higher order allocations must be able to be treated as > * indepdenent small pages by callers (as they can with > -- > 2.30.2 > Reviewed-by: Uladzislau Rezki (Sony) -- Uladzislau Rezki