From nobody Tue Apr 7 05:58:51 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1AD30388361; Mon, 16 Mar 2026 11:32:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773660759; cv=none; b=CH5AuNN7bqAmf8bPhGSfBjGut86Dbe2DJH5ej2pBbaDNTwjX4lJoFy2isdZthvJ1izFIuvVt7BjZfXMX3onClbgdx/BhIwShpXk+TVi226P3cmfAxFqIrJFk5FTX/JjhEcxjivBm0spFXaWYPCmVcI7/qwEXzu2y8t/dQf+oSOM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773660759; c=relaxed/simple; bh=nbYpfaEAsn7PoS9SB1y3ioIZ4TDt//kylLT/jdFXuaQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=f/JLFiVSoi8sGdslMVN9DDKyxAMi7FHNd5Ss4N3NXWjX82Dd7uVwmHsemPx2SOEMN/EMT+LicnDckvvwCIoRmaQOfGsOoPQ06/X5z3i7uSBzdrWEldtH3zt6ZSg1L5qUWWscpZm0OKW44UxGlD+OjNQdeu5R9AEEdMlR2sRRze0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4DD0E1477; Mon, 16 Mar 2026 04:32:31 -0700 (PDT) Received: from e142334-100.cambridge.arm.com (e142334-100.cambridge.arm.com [10.1.194.63]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 0BC0E3F778; Mon, 16 Mar 2026 04:32:34 -0700 (PDT) From: Muhammad Usama Anjum To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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_cont= ig_frozen_range | |--70.20%--free_contig_frozen_range | | | |--46.41%--__free_frozen_pages | | | | | --36.18%--free_frozen_page_commit | | | | | --29.63%--_raw_spin_unlock_ir= qrestore | | | |--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_cont= ig_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 Reviewed-by: Vlastimil Babka (SUSE) Reviewed-by: Zi Yan --- 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) =20 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 =3D pfn_to_page(pfn); + struct page *start =3D NULL; + unsigned long i; + + for (i =3D 0; i < nr_pages; i++, page++) { + if (free_pages_prepare(page, 0)) { + if (!start) + start =3D page; + } else if (start) { + free_prepared_contig_range(start, page - start); + start =3D NULL; + } + } + + if (start) + free_prepared_contig_range(start, page - start); } =20 /** --=20 2.47.3