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From: Shakeel Butt To: Kent Overstreet Cc: Usama Arif , Andrew Morton , surenb@google.com, hannes@cmpxchg.org, vlad.wing@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 1/2] mm: slub: allocate slab object extensions non-contiguously Message-ID: References: <20250520122547.1317050-1-usamaarif642@gmail.com> <3divtzm4iapcxwbzxlmfmg3gus75n3rqh43vkjnog456jm2k34@f3rpzvcfk3p6> <6d015d91-e74c-48b3-8bc3-480980a74f9b@gmail.com> <22oihuvcrh5sg3urocw6wbop2v5yni7zinuhywbz7glsee4yoa@gzi5v5fcggdl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <22oihuvcrh5sg3urocw6wbop2v5yni7zinuhywbz7glsee4yoa@gzi5v5fcggdl> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 66080C0009 X-Rspam-User: X-Stat-Signature: gz7fceznnaxz7txm4bj5nqt6c571pdos X-HE-Tag: 1747751087-450323 X-HE-Meta: U2FsdGVkX18xFPw8p3gOEAgFpvX4+iB9TAXceOltkeowE4IRbSyoaECGtMwmUdVtlYtk1gTRF8TUX1Z6k9kzJE7eqwfI40l5kmW+2y5X6/u/2xZS55vee2iIDvdXvEdiLQfIVVmJWYiKMyYNNlYaPmcJI1cF8yxlyD4kBnqaxZC8b8GTOq6WoQHGC3NSGfY0yB6NdbUK7zeemERFRwxBsWylxAAAXGmFKvPF131K3yHM12tieFOTb6yniglmYFZ2pwXr2T5l7TMAUfQQmrQD/Wd+/UZ4j6vgJ6vco8dPWMMDDMfi7m83Pw0gDUJVSoiKTqxWO+gw87zCGDubeNfJGwjJFSp8IKXGeiaz9pFo+HTiIXhPPVF5uEc9G9zgtt8e79oeRX/1uFuwEL/ypme4rY2S7uP/TYdno/Kei5/LiTd/jcCoM0DdD552goo5/RXyLzGExdDbDHQkjSY+CYjjjiehzdJTCXv3AfIDHqULFbg5X2nV6WS9XVMPS6rJWaFyX35MChzOlgnBwyK2033hUWbTO4mQ8lXzQyVYSC2Xu4swRnPqE49tmsv+Ti53EtWJFNLPIJbK9HCxdDUaaw3uv+zfeBKDlvg6Ead5HE94Ya52SCH2Rt0EPmb/4kPY9a/UBhjhqICfRK2Z5un91i4Xt7kaVXKZhYMxp9lg7+alPbeLQ1iJgyCfBwuxmnkClB9FCejrhky+SfAbHLod/cb0HVy133bNAZCBL765gOr7KMHz6X3qUleONEZ6sBEY8a93Q1BLzq7MVVi9/mq5FsIvbAVwZR9SqZhfEMN5AB20aqE5/ARqfYj/P2AId5DkCjBoLiQh09TWeK1SHmmJZS45Ho5MEjG+BajF1I6IDcBFIutJ85LtEJ9c0OzxN4B6vLywEpEGf7qY3BHCZ2ZJjVWeR9M3r4FrrD+9nidW18D0bn9zhyY4jA92BVsIBHclIZvqCeuBMyxFIZUY+ENPCIU IXRPUb5A aEj/DT75qr8gMU53+LdCas4Om+iWBUiVXXjK1Ud6DlDNAPrcUqcNl1r9Al9sZCU+8if1MpQXxxtkStDVuy64M4lbruatVTcpL+Aaol+jcf6aR+deCPT9JRUQFdIcBdb+SoEsPWmc3LRVH5GBDzgqQSmjlXcuGDODVe+1gmpI8ZQFRaS8jtiHq20c7nE3X3vE0L72OcOpneTLA08IVYVX72TaDK51QdDzziJmTjJJsBS68edg3/DlcVAXhSpwidktmNgi7jDu3HV7o7kAnQ1IK0//eCF2rGUUqbV1PmUwkoVt/k4rJFYrYcySzDhKLJQaIQHxM+S+8Ok4jFeA= 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 Tue, May 20, 2025 at 10:01:27AM -0400, Kent Overstreet wrote: > On Tue, May 20, 2025 at 02:46:14PM +0100, 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? > > Our behaviour when thrashing sucks, we don't want to do anything to make > that worse. > > There's also the fact that vmalloc doesn't correctly respect gfp flags, > so until that gets fixed this doesn't work at all. Which gfp flags vmalloc is not respecting today?