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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1747640922; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references; bh=vRwlAFhQaOa6OKdw30la2cac+LHun1qtiEK+lD7gygs=; b=2m4LuQ5FbrpAcqu0ebe5gd/303d6ToXf7lbzlYCLVs6xxvSNWkMmLNVrEjbWvg8k9dCftD I8IX+c3TN/RT0ITqMGLDYamXg0ZN99pXhgbF8cSMl0qJXPTQKTR1855q8YIs8mN67pv0Ik k347vYghMMIMiw9PuQw36vgC4lu+mnk= 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 2580D14BF; Mon, 19 May 2025 00:48:28 -0700 (PDT) Received: from K4MQJ0H1H2.blr.arm.com (unknown [10.164.18.48]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 6A31F3F6A8; Mon, 19 May 2025 00:48:34 -0700 (PDT) From: Dev Jain To: akpm@linux-foundation.org Cc: ryan.roberts@arm.com, david@redhat.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, anshuman.khandual@arm.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com, Dev Jain Subject: [PATCH v3 0/5] Optimize mprotect() for large folios Date: Mon, 19 May 2025 13:18:19 +0530 Message-Id: <20250519074824.42909-1-dev.jain@arm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2797B18000E X-Stat-Signature: m7y96rj3ugg9j3di671m8ouipk9owqpe X-HE-Tag: 1747640921-775781 X-HE-Meta: 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 IJpJvvaF 8wY1MW7qhMS+NksoJRJYsZenGK/3Z08gSroy1B8mcg6oA0PLzgt/d1lfi7MQw912XKa4xVmPmL91lCLs4b5NmaOZ0T/UuVEmvg6mk X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This patchset optimizes the mprotect() system call for large folios by PTE-batching. We use the following test cases to measure performance, mprotect()'ing the mapped memory to read-only then read-write 40 times: Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then pte-mapping those THPs Test case 2: Mapping 1G of memory with 64K mTHPs Test case 3: Mapping 1G of memory with 4K pages Average execution time on arm64, Apple M3: Before the patchset: T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds After the patchset: T1: 2.1 seconds T2: 2.2 seconds T3: 4.3 seconds Observing T1/T2 and T3 before the patchset, we also remove the regression introduced by ptep_get() on a contpte block. And, for large folios we get an almost 74% performance improvement, albeit the trade-off being a slight degradation in the small folio case. Here is the test program: #define _GNU_SOURCE #include #include #include #include #include #define SIZE (1024*1024*1024) unsigned long pmdsize = (1UL << 21); unsigned long pagesize = (1UL << 12); static void pte_map_thps(char *mem, size_t size) { size_t offs; int ret = 0; /* PTE-map each THP by temporarily splitting the VMAs. */ for (offs = 0; offs < size; offs += pmdsize) { ret |= madvise(mem + offs, pagesize, MADV_DONTFORK); ret |= madvise(mem + offs, pagesize, MADV_DOFORK); } if (ret) { fprintf(stderr, "ERROR: mprotect() failed\n"); exit(1); } } int main(int argc, char *argv[]) { char *p; int ret = 0; p = mmap((1UL << 30), SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (p != (1UL << 30)) { perror("mmap"); return 1; } memset(p, 0, SIZE); if (madvise(p, SIZE, MADV_NOHUGEPAGE)) perror("madvise"); explicit_bzero(p, SIZE); pte_map_thps(p, SIZE); for (int loops = 0; loops < 40; loops++) { if (mprotect(p, SIZE, PROT_READ)) perror("mprotect"), exit(1); if (mprotect(p, SIZE, PROT_READ|PROT_WRITE)) perror("mprotect"), exit(1); explicit_bzero(p, SIZE); } } The patchset is rebased onto mm-unstable (9ead4336d7c07f085def6ab372245640a22af5bd). v2->v3: - Add comments for the new APIs (Ryan, Lorenzo) - Instead of refactoring, use a "skip_batch" label - Move arm64 patches at the end (Ryan) - In can_change_pte_writable(), check AnonExclusive page-by-page (David H) - Resolve implicit declaration; tested build on x86 (Lance Yang) v1->v2: - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the header more resilient) - Abridge the anon-exclusive condition (Lance Yang) Dev Jain (5): mm: Optimize mprotect() by batch-skipping PTEs mm: Add batched versions of ptep_modify_prot_start/commit mm: Optimize mprotect() by PTE batching arm64: Add batched version of ptep_modify_prot_start arm64: Add batched version of ptep_modify_prot_commit arch/arm64/include/asm/pgtable.h | 10 ++ arch/arm64/mm/mmu.c | 21 ++++- include/linux/mm.h | 7 +- include/linux/pgtable.h | 79 ++++++++++++++++ mm/mprotect.c | 154 +++++++++++++++++++++++++------ mm/pgtable-generic.c | 16 +++- 6 files changed, 246 insertions(+), 41 deletions(-) -- 2.30.2