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Mon, 15 May 2023 11:29:19 +0100 From: David Laight To: 'Kent Overstreet' , Eric Biggers CC: Lorenzo Stoakes , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-bcachefs@vger.kernel.org" , Kent Overstreet , Andrew Morton , Uladzislau Rezki , "linux-mm@kvack.org" Subject: RE: [PATCH 07/32] mm: Bring back vmalloc_exec Thread-Topic: [PATCH 07/32] mm: Bring back vmalloc_exec Thread-Index: AQHZhidTKdvNQYED30e4lpVLdXSS2q9bIbmQ Date: Mon, 15 May 2023 10:29:18 +0000 Message-ID: <1f1d88a6a33f4e5db99544fda965c594@AcuMS.aculab.com> References: <20230509165657.1735798-1-kent.overstreet@linux.dev> <20230509165657.1735798-8-kent.overstreet@linux.dev> <20230510064849.GC1851@quark.localdomain> <20230513015752.GC3033@quark.localdomain> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: DA8CF12000D X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: i7moen3kj7dubif7uay8pcbeyaknerbm X-HE-Tag: 1684146562-723330 X-HE-Meta: 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 PQDTBePf piuXAxnwPyL+ltKD4Qn4cYtgbGlomBSePAFX4JpZB9rpV2Zg/XsX5Gtchogime+/P/tvLYonaxOcQrGnhYWrudzvBLFjLrjPHuhrQRQCZWmW7k8FFPsqF06QUYPMP6pUydSwPbFP5U2iPbuWIlUVNHj5FW/d/KaoCtzUw2UM8JgwZ7Ytvo5UktPyLXHsfMUzSiLWPunHrCgmS+vAdb+pIMxNujhTDcR3yqHZ+nHDwd3titwXix99OxFQMYRPnH69x2cCPIUldA+7qoHO6XFL4MY3fKx3FFnCjuD3n4O26TSVCQhpqEfQLwjWFxDGdJ3rj55CddpzbXx5ny+Sy3Z0j0Y+6PJr+28P3pZGa X-Bogosity: Ham, tests=bogofilter, spamicity=0.000068, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Kent Overstreet > Sent: 14 May 2023 06:45 ... > dynamically generated unpack: > rand_insert: 20.0 MiB with 1 threads in 33 sec, 1609 nsec per iter, 6= 07 KiB per sec >=20 > old C unpack: > rand_insert: 20.0 MiB with 1 threads in 35 sec, 1672 nsec per iter, 5= 84 KiB per sec >=20 > the Eric Biggers special: > rand_insert: 20.0 MiB with 1 threads in 35 sec, 1676 nsec per iter, 5= 83 KiB per sec >=20 > Tested two versions of your approach, one without a shift value, one > where we use a shift value to try to avoid unaligned access - second was > perhaps 1% faster You won't notice any effect of avoiding unaligned accesses on x86. I think then get split into 64bit accesses and again on 64 byte boundaries (that is what I see for uncached access to PCIe). The kernel won't be doing >64bit and the 'out of order' pipeline will tend to cover the others (especially since you get 2 reads/clock). > so it's not looking good. This benchmark doesn't even hit on > unpack_key() quite as much as I thought, so the difference is > significant. Beware: unless you manage to lock the cpu frequency (which is ~impossible on some cpu) timings in nanoseconds are pretty useless. You can use the performance counter to get accurate cycle times (provided there isn't a cpu switch in the middle of a micro-benchmark). =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)