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([2620:10d:c092:500::7:66a9]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6004d4f5fe5sm7232206a12.7.2025.05.20.07.13.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 May 2025 07:13:45 -0700 (PDT) Message-ID: Date: Tue, 20 May 2025 15:13:44 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: slub: allocate slab object extensions non-contiguously From: Usama Arif To: Kent Overstreet Cc: Andrew Morton , surenb@google.com, hannes@cmpxchg.org, shakeel.butt@linux.dev, vlad.wing@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20250520122547.1317050-1-usamaarif642@gmail.com> <3divtzm4iapcxwbzxlmfmg3gus75n3rqh43vkjnog456jm2k34@f3rpzvcfk3p6> <6d015d91-e74c-48b3-8bc3-480980a74f9b@gmail.com> Content-Language: en-US In-Reply-To: <6d015d91-e74c-48b3-8bc3-480980a74f9b@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Stat-Signature: 19e3935u5c3m83bitznppndw6tf6smyt X-Rspamd-Queue-Id: D50F61A0002 X-Rspam-User: X-HE-Tag: 1747750427-926789 X-HE-Meta: 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 fpz1TYXL 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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: List-Subscribe: List-Unsubscribe: On 20/05/2025 14:46, Usama Arif wrote: > > > On 20/05/2025 14:44, Kent Overstreet wrote: >> On Tue, May 20, 2025 at 01:25:46PM +0100, Usama Arif wrote: >>> When memory allocation profiling is running on memory bound services, >>> allocations greater than order 0 for slab object extensions can fail, >>> for e.g. zs_handle zswap slab which will be 512 objsperslab x 16 bytes >>> per slabobj_ext (order 1 allocation). Use kvcalloc to improve chances >>> of the allocation being successful. >>> >>> Signed-off-by: Usama Arif >>> Reported-by: Vlad Poenaru >>> Closes: https://lore.kernel.org/all/17fab2d6-5a74-4573-bcc3-b75951508f0a@gmail.com/ >>> --- >>> mm/slub.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/mm/slub.c b/mm/slub.c >>> index dc9e729e1d26..bf43c403ead2 100644 >>> --- a/mm/slub.c >>> +++ b/mm/slub.c >>> @@ -1989,7 +1989,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, >>> gfp &= ~OBJCGS_CLEAR_MASK; >>> /* Prevent recursive extension vector allocation */ >>> gfp |= __GFP_NO_OBJ_EXT; >>> - vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp, >>> + vec = kvcalloc_node(objects, sizeof(struct slabobj_ext), gfp, >>> slab_nid(slab)); >> >> And what's the latency going to be on a vmalloc() allocation when we're >> low on memory? > > Would it not be better to get the allocation slighly slower than to not get > it at all? Also a majority of them are less than 1 page. kvmalloc of less than 1 page falls back to kmalloc. So vmalloc will only be on those greater than 1 page size, which are in the minority (for e.g. zs_handle, request_sock_subflow_v6, request_sock_subflow_v4...).