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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: <20260331152208.975266-1-usama.anjum@arm.com> <20260331152208.975266-3-usama.anjum@arm.com> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20260331152208.975266-3-usama.anjum@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A7791180004 X-Stat-Signature: eto68fyf469z6p33gdqwyr1nwz386bzx X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775035176-290613 X-HE-Meta: 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 XPjTpak9 jqMkzigMBY9Agv3Lq2QIZstTnCyESpwUHUhGAZJlt4GvGPHII2ubiRot21dKvfpMawtsUuavVjORlqnISm4HuC6FnPJWmI4NaY/ki/QCTAVU+92Su5Ns3l3wc/OhdzbZECo/OzVoMzPdrlpmXzfEwlhooC+68YhF0p4v/KpbnwrIRXwDH60ZJ6J2qSmaViP09xQ2vWIeZ0Pe7xC3cxLVb7Kq74UTLgF9CJBn+M17rhOt34gfplxisU8E9j+cwScI289pfZpFSw7ml8tjLHxnXm0ynE28bdSv/M9PRMGvwhfXFw6tmyQtyeiezlERNozhrtIZD6OiOZxV05mNT0LEf9kuegLBTIdjYvLiTZFUGD/DLcgfN+GxeQq6XWPC6bcI8QsXBQEnm//lY+sX/Hetfd2IY9S/X0HswVi/6SiQaoYG+YMF4B2hCVqq+qg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Nit: the subject could be more specific, e.g. like this? vmalloc: Optimize vfree with free_pages_bulk() On 3/31/26 17:22, 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) > +void free_pages_bulk(struct page **page_array, unsigned long nr_pages) > +{ > + while (nr_pages) { > + unsigned long nr_contig = num_pages_contiguous(page_array, nr_pages); > + > + __free_contig_range(page_to_pfn(*page_array), nr_contig); I'll note that num_pages_contiguous() already handled crossing the section boundaries and __free_contig_range() checks them again. But that's fine I think, we don't have to optimize for !SPARSEMEM_VMEMMAP architectures and on SPARSEMEM_VMEMMAP the checks should be compiled out, right. It would complicate the API otherwise. > + > + nr_pages -= nr_contig; > + page_array += nr_contig; > + cond_resched(); > + } > +} > + > /* > * This is the 'heart' of the zoned buddy allocator. > */