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Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Uladzislau Rezki , Nick Terrell , David Sterba , Vishal Moola , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com References: <20260327125720.2270651-1-usama.anjum@arm.com> <20260327125720.2270651-3-usama.anjum@arm.com> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20260327125720.2270651-3-usama.anjum@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: AA57A180013 X-Stat-Signature: a6redb61fx1t38ucasbj7s94he6dtj8w X-Rspam-User: X-HE-Tag: 1774881350-643716 X-HE-Meta: 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 ruTqPFwk QZ2wcuYquJ3QEkqfTYsEmd44YlS+yL8JCtCc7aJsSCurQWSeYAHAjDf+bIlZtHmNsyhPR/Vx6a/w+AZLyP3VBqvPEMbuaCGStDTh45r+T/VwNaiNmfuQFIZtV1ArxfdahN6U6rqFsjNjQydtJ7Lsu66LALkED9KVWL5sAWfD93T8mJhvKAFOjWXcll7CvWBfEFKaihEbxCbVA+6dyLhpmwhZHHXO+hqYohOaCW5imT3GxEBVv92XKMWZWh18HqZ2fS14iXZSBCQ8/VDYN3yDQCRCSWOl/RM+Q2tLW5TLdopkpLgrYBnYQxYc3QG9/tdXQyNSkgzFwojqVM3JRpKHz8/vKekmEafZvveFTId2AEOx20QuQVB0t7SovsC42Tb7a8/S2cmEIpjr/h6g= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/27/26 13:57, Muhammad Usama Anjum wrote: > From: Ryan Roberts > > Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it > must immediately split_page() to order-0 so that it remains compatible > with users that want to access the underlying struct page. > Commit a06157804399 ("mm/vmalloc: request large order pages from buddy > allocator") recently made it much more likely for vmalloc to allocate > high order pages which are subsequently split to order-0. > > Unfortunately this had the side effect of causing performance > regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko > benchmarks). See Closes: tag. This happens because the high order pages > must be gotten from the buddy but then because they are split to > order-0, when they are freed they are freed to the order-0 pcp. > Previously allocation was for order-0 pages so they were recycled from > the pcp. > > It would be preferable if when vmalloc allocates an (e.g.) order-3 page > that it also frees that order-3 page to the order-3 pcp, then the > regression could be removed. > > So let's do exactly that; update stats separately first as coalescing is > hard to do correctly without complexity. Use free_pages_bulk() which uses > the new __free_contig_range() API to batch-free contiguous ranges of pfns. > This not only removes the regression, but significantly improves > performance of vfree beyond the baseline. > > A selection of test_vmalloc benchmarks running on arm64 server class > system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request > large order pages from buddy allocator") was added in v6.19-rc1 where we > see regressions. Then with this change performance is much better. (>0 > is faster, <0 is slower, (R)/(I) = statistically significant > Regression/Improvement): > > +-----------------+----------------------------------------------------------+-------------------+--------------------+ > | Benchmark | Result Class | mm-new | this series | > +=================+==========================================================+===================+====================+ > | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% | > | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% | > | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% | > | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% | > | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% | > | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% | > | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% | > | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% | > | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% | > | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% | > | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% | > | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% | > | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% | > | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% | > | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% | > | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% | > | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% | > | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% | > | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% | > +-----------------+----------------------------------------------------------+-------------------+--------------------+ > > Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator") > Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/ > Acked-by: Zi Yan > Signed-off-by: Ryan Roberts > Co-developed-by: Muhammad Usama Anjum > Signed-off-by: Muhammad Usama Anjum Acked-by: Vlastimil Babka (SUSE)