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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 , 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 v3 3/3] mm/page_alloc: Optimize __free_contig_frozen_range() Date: Tue, 24 Mar 2026 13:35:34 +0000 Message-ID: <20260324133538.497616-4-usama.anjum@arm.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260324133538.497616-1-usama.anjum@arm.com> References: <20260324133538.497616-1-usama.anjum@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 211F040008 X-Stat-Signature: jx39iixeocnp4q76hr7soexbpuqyjgoe X-Rspam-User: X-HE-Tag: 1774359358-269731 X-HE-Meta: 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 c8k6tJ/3 MJxCQJHTIkuCASfZtJDgSB5Q7dLcm1cy489OBPs2W1DvXwBFdUnBdB/dPEqdXvClPkIDaFS70nGEtcNL6ripH85j9egAGucWXVPWXwk5dTAvAU+fK547GtQKpVowR9thGySCnOl4dsWLJzPP82IX0wa8oG6nlE0CKcvjPcsppyQlISefX8spPWVxnZXKRB7DnSgOz+BBXEDAhNw3Fk7JPxksfo/cjL2our3m7KHH99F2GCz978y+A4H5v6mLbkkjZODXejkYPLww41Z/V12VCN56FEgnr2lrqSz/aTLdKyQbO+uisw+RucOJH2shN5yyd9uatH6vT4Jq6z2sRY77QFDDZtcBGisN9ipupXwdASz0u9zrrH305HJ/yRylcnFgjrTvr 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 --- Changes since v2: - Rework the loop to check for memory sections just like __free_contig_range() - Didn't add reviewed-by tags because of rework --- mm/page_alloc.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 250cc07e547b8..26eac35ef73bd 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7038,8 +7038,30 @@ 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 start_sec; + unsigned long i; + + for (i = 0; i < nr_pages; i++, page++) { + if (!free_pages_prepare(page, 0)) { + if (start) { + free_prepared_contig_range(start, page - start); + start = NULL; + } + } else if (start && + memdesc_section(page->flags) != start_sec) { + free_prepared_contig_range(start, page - start); + start = page; + start_sec = memdesc_section(page->flags); + } else if (!start) { + start = page; + start_sec = memdesc_section(page->flags); + } + } + + if (start) + free_prepared_contig_range(start, page - start); } /** -- 2.47.3