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b=tF6VIh2NGztTz8j/GldWe58g5f5QqvEyYmFNuGIA72367L4gYrgGcHFfR5sGvT1NN jcOJ7lRGh4r+rmQ5QhfztpZqqdv5uOnaI+jq1hjgCXRmZClbK2H96DHL3hvyD+7g8O 8xcy4nIKS0qqfTGgGd3shk0pT49MogJn4ynP4DOI= Date: Sun, 29 Jun 2025 16:05:49 -0700 From: Andrew Morton To: Dev Jain 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 Subject: Re: [PATCH v4 0/4] Optimize mprotect() for large folios Message-Id: <20250629160549.da922e78d202c510a1ec68f8@linux-foundation.org> In-Reply-To: <20250628113435.46678-1-dev.jain@arm.com> References: <20250628113435.46678-1-dev.jain@arm.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7CF1210000A X-Stat-Signature: c1kwdyoy4dqj4qxtjmxk9ntck4snrqmr X-HE-Tag: 1751238351-455195 X-HE-Meta: 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 l7tmm/An pPcWhONySpSgiS0nIqwgrE081yZNPLgojmN9grN+73WhuqI3oJ9IijguOhWoRiN0a4+vTe3ld73Efds+RdO3K+WHJaH9uLSDz0XTvlrzOsue3vlDPqmOvtgOlgM4c0W2Xddvzl7J0777fXQ4qZIDyiYdWdryKVTTPGoccGQ74R2XD5PHZqWo9m2fYJK2TCLqUEKpgpDGnoNSxg38Ti20m8Sd/8x+diZOz4O7Ukh8Pw45JLIedLqCzfWXe1+ue+nPvqqNfumfgQQ7QzVNx/U5nMEbHQVkab/Y+LBqVIr8aG2BVH84gFmdv1dQx0g== 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: On Sat, 28 Jun 2025 17:04:31 +0530 Dev Jain wrote: > This patchset optimizes the mprotect() system call for large folios > by PTE-batching. No issues were observed with mm-selftests, build > tested on x86_64. um what. Seems to claim that "selftests still compiles after I messed with stuff", which isn't very impressive ;) Please clarify? > 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 Well that's tasty. > 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. >