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[95.203.18.139]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-59b7a0ca367sm3018309e87.38.2026.01.12.02.49.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jan 2026 02:49:52 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 12 Jan 2026 11:49:50 +0100 To: Dev Jain Cc: catalin.marinas@arm.com, will@kernel.org, urezki@gmail.com, akpm@linux-foundation.org, tytso@mit.edu, adilger.kernel@dilger.ca, cem@kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, shijie@os.amperecomputing.com, yang@os.amperecomputing.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, npiggin@gmail.com, willy@infradead.org, david@kernel.org, ziy@nvidia.com Subject: Re: [RESEND RFC PATCH 0/2] Enable vmalloc huge mappings by default on arm64 Message-ID: References: <20251212042701.71993-1-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251212042701.71993-1-dev.jain@arm.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3B12C100006 X-Stat-Signature: 1wrra8i98byxuxtzxw1bwciikzr19oc7 X-Rspam-User: X-HE-Tag: 1768215488-513129 X-HE-Meta: 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 IVy8Eg3I 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 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 Fri, Dec 12, 2025 at 09:56:59AM +0530, Dev Jain wrote: > In the quest for reducing TLB pressure via block mappings, enable huge > vmalloc by default on arm64 for BBML2-noabort systems which support kernel > live mapping split. > > This series is an RFC, because I cannot get a performance improvement for > the usual benchmarks which we have. Currently, vmalloc follows an opt-in > approach for block mappings - the users calling vmalloc_huge() are the ones > which expect the most advantage from block mappings. Most users of > vmalloc(), kvmalloc() and kvzalloc() map a single page. After applying this > series, it is expected that a considerable number of users will produce > cont mappings, and probably none will produce PMD mappings. > > I am asking for help from the community in testing - I believe that one of > the testing methods is xfstests: a lot of code uses the APIs mentioned > above. I am hoping that someone can jump in and run at least xfstests, and > probably some other tests which can take advantage of the reduced TLB > pressure from vmalloc cont mappings. > I checked how often vmalloc/vmap is triggered when i run xfstests. I think it also depends on env. and can be different from one setup to another. "echo vmalloc:alloc_vmap_area > set_event" urezki@milan:~/data/optane/xfs-test/xfstests.git$ wc -l ./vmalloc_traces/*.trace 2875 ./vmalloc_traces/generic_036.trace 30117 ./vmalloc_traces/generic_038.trace 8481 ./vmalloc_traces/generic_051.trace 16986 ./vmalloc_traces/generic_055.trace 6079 ./vmalloc_traces/generic_068.trace 2792 ./vmalloc_traces/generic_070.trace 26945 ./vmalloc_traces/generic_072.trace 2772 ./vmalloc_traces/generic_076.trace 2750 ./vmalloc_traces/generic_083.trace 3319 ./vmalloc_traces/generic_095.trace 2855 ./vmalloc_traces/generic_232.trace 3537 ./vmalloc_traces/generic_269.trace 21265 ./vmalloc_traces/generic_299.trace 3231 ./vmalloc_traces/generic_300.trace 3050 ./vmalloc_traces/generic_323.trace 2831 ./vmalloc_traces/generic_390.trace 4296 ./vmalloc_traces/generic_461.trace 4807 ./vmalloc_traces/generic_476.trace 3198 ./vmalloc_traces/generic_551.trace 3096 ./vmalloc_traces/generic_616.trace 6495 ./vmalloc_traces/generic_627.trace 11232 ./vmalloc_traces/generic_642.trace 11706 ./vmalloc_traces/generic_650.trace 3135 ./vmalloc_traces/generic_750.trace 5926 ./vmalloc_traces/generic_751.trace 77623 ./vmalloc_traces/xfs_013.trace 9172 ./vmalloc_traces/xfs_017.trace 4145 ./vmalloc_traces/xfs_068.trace 2982 ./vmalloc_traces/xfs_104.trace 7293 ./vmalloc_traces/xfs_167.trace 18851 ./vmalloc_traces/xfs_168.trace 4373 ./vmalloc_traces/xfs_442.trace 3550 ./vmalloc_traces/xfs_609.trace 321765 total urezki@milan:~/data/optane/xfs-test/xfstests.git$ Time execution is different for each test. For example "xfs_013" test takes around 200 seconds on my system and is in top of number of calls: 77623 / 200 = 388.115 calls/sec 200 / 77623 = 0.002576 = ~each 2.5ms Please note, i have not checked impact of your patch on time execution or how TLB pressure is affected. -- Uladzislau Rezki