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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Uladzislau Rezki , Nick Terrell , David Sterba , "Vishal Moola (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com Cc: Muhammad Usama Anjum Subject: [PATCH v2 3/3] mm/page_alloc: Optimize __free_contig_frozen_range() Date: Mon, 16 Mar 2026 11:31:44 +0000 Message-ID: <20260316113209.945853-4-usama.anjum@arm.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260316113209.945853-1-usama.anjum@arm.com> References: <20260316113209.945853-1-usama.anjum@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 9337310000A X-Stat-Signature: 93ijruwag5qzzdhrjihciu5zqqpm6ix5 X-Rspam-User: X-HE-Tag: 1773660758-420981 X-HE-Meta: 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 N2cGp8gl kIFTQdXVd40pD6e/rqklhqnV969PiJ5Uzo7otLbhahbC64pN5VGHxPRrmGDB2aLwb+ueZBuMJT1voL6leM+fXMJvGnGSYNX5kaDATNR6qLvUIS4BHxhrDlTlL4JGLAh0Zs1Vr0Znoxpdm4zfOjtO/zNbZpsaeteUEExmQhgs/FBDcexeMQS2OfLBnD91TbZDRaWZ5Tqfad+xBIKq7UYwvNXMR5IkZe8KO8Chsk4UGn/bpqhBeTC5cwgIAhvJNRg0KzBMlJcM9uzoqJlGoYl+1GlFiWTE/+aSD1oE9e8s2Q3bGTeM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Apply the same batch-freeing optimization from free_contig_range() to the frozen page path. The previous __free_contig_frozen_range() freed each order-0 page individually via free_frozen_pages(), which is slow for the same reason the old free_contig_range() was: each page goes to the order-0 pcp list rather than being coalesced into higher-order blocks. Rewrite __free_contig_frozen_range() to call free_pages_prepare() for each order-0 page, then batch the prepared pages into the largest possible power-of-2 aligned chunks via free_prepared_contig_range(). If free_pages_prepare() fails (e.g. HWPoison, bad page) the page is deliberately not freed; it should not be returned to the allocator. I've tested CMA through debugfs. The test allocates 16384 pages per allocation for several iterations. There is 3.5x improvement. Before: 1406 usec per iteration After: 402 usec per iteration Before: 70.89% 0.69% cma [kernel.kallsyms] [.] free_contig_frozen_range | |--70.20%--free_contig_frozen_range | | | |--46.41%--__free_frozen_pages | | | | | --36.18%--free_frozen_page_commit | | | | | --29.63%--_raw_spin_unlock_irqrestore | | | |--8.76%--_raw_spin_trylock | | | |--7.03%--__preempt_count_dec_and_test | | | |--4.57%--_raw_spin_unlock | | | |--1.96%--__get_pfnblock_flags_mask.isra.0 | | | --1.15%--free_frozen_page_commit | --0.69%--el0t_64_sync After: 23.57% 0.00% cma [kernel.kallsyms] [.] free_contig_frozen_range | ---free_contig_frozen_range | |--20.45%--__free_contig_frozen_range | | | |--17.77%--free_pages_prepare | | | --0.72%--free_prepared_contig_range | | | --0.55%--__free_frozen_pages | --3.12%--free_pages_prepare Suggested-by: Zi Yan Signed-off-by: Muhammad Usama Anjum --- mm/page_alloc.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6a9430f720579..2e99fa85cdc8e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7020,8 +7020,22 @@ static int __alloc_contig_verify_gfp_mask(gfp_t gfp_mask, gfp_t *gfp_cc_mask) static void __free_contig_frozen_range(unsigned long pfn, unsigned long nr_pages) { - for (; nr_pages--; pfn++) - free_frozen_pages(pfn_to_page(pfn), 0); + struct page *page = pfn_to_page(pfn); + struct page *start = NULL; + unsigned long i; + + for (i = 0; i < nr_pages; i++, page++) { + if (free_pages_prepare(page, 0)) { + if (!start) + start = page; + } else if (start) { + free_prepared_contig_range(start, page - start); + start = NULL; + } + } + + if (start) + free_prepared_contig_range(start, page - start); } /** -- 2.47.3