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Thu, 12 Jun 2025 12:13:57 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id nJOpKIXESmhTcgAAD6G6ig (envelope-from ); Thu, 12 Jun 2025 12:13:57 +0000 Date: Thu, 12 Jun 2025 13:13:52 +0100 From: Pedro Falcato To: Dev Jain Cc: akpm@linux-foundation.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@redhat.com, peterx@redhat.com, ryan.roberts@arm.com, mingo@kernel.org, libang.li@antgroup.com, maobibo@loongson.cn, zhengqi.arch@bytedance.com, baohua@kernel.org, anshuman.khandual@arm.com, willy@infradead.org, ioworker0@gmail.com, yang@os.amperecomputing.com, baolin.wang@linux.alibaba.com, ziy@nvidia.com, hughd@google.com Subject: Re: [PATCH v4 2/2] mm: Optimize mremap() by PTE batching Message-ID: References: <20250610035043.75448-1-dev.jain@arm.com> <20250610035043.75448-3-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250610035043.75448-3-dev.jain@arm.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: ABD4440006 X-Stat-Signature: sejthb8ttpoe3pwiprj1kashut3zhqcj X-HE-Tag: 1749730441-70316 X-HE-Meta: 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 Vs4OER08 O0qy9VH+FSnf5TnJ+WAvV+Y6EWGLnDtIoBnF4e7GNN2lNiQE0lLK/sdUB7GaDTjpMlZ8XIUtw9sGfvGw/6dg88EEvpUdjkbVLcLKQOa6SC9e5GxE9HYbj/vrRbJfOYDD7GP5O4+VziPLxM5UMz7PrfFX2POoEtsk+5NRNKKWDMfhdto2vHajDmM1Tx6OPkXANsV5YhYBMb6xg/Jvt9Ff+pK9Do5DNR3qMlagAE73riB4TeNPF//unkDpQ9zJsZL06mBuh4GO0DnZKdibdw/BQwuKzI5l3qPdI8Hkj75USmjCAdzxLQaL5AhE5ojXT7dSPecFDMlgq8pdqdM8qTZ9JidY2crIUD7wOUGz0ZEZOdZzRPYQ= 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 Tue, Jun 10, 2025 at 09:20:43AM +0530, Dev Jain wrote: > Use folio_pte_batch() to optimize move_ptes(). On arm64, if the ptes > are painted with the contig bit, then ptep_get() will iterate through all 16 > entries to collect a/d bits. Hence this optimization will result in a 16x > reduction in the number of ptep_get() calls. Next, ptep_get_and_clear() > will eventually call contpte_try_unfold() on every contig block, thus > flushing the TLB for the complete large folio range. Instead, use > get_and_clear_full_ptes() so as to elide TLBIs on each contig block, and only > do them on the starting and ending contig block. > > For split folios, there will be no pte batching; nr_ptes will be 1. For > pagetable splitting, the ptes will still point to the same large folio; > for arm64, this results in the optimization described above, and for other > arches (including the general case), a minor improvement is expected due to > a reduction in the number of function calls. > > Signed-off-by: Dev Jain Reviewed-by: Pedro Falcato -- Pedro