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[90.233.206.146]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-2f615183134sm19376071fa.122.2024.09.02.10.03.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Sep 2024 10:03:04 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 2 Sep 2024 19:03:02 +0200 To: Christophe JAILLET Cc: Uladzislau Rezki , Adrian Huang , Andrew Morton , Christoph Hellwig , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Adrian Huang Subject: Re: [PATCH 1/1] mm: vmalloc: Optimize vmap_lazy_nr arithmetic when purging each vmap_area Message-ID: References: <20240829130633.2184-1-ahuang12@lenovo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: A0AC3C0008 X-Rspamd-Server: rspam01 X-Stat-Signature: zhq1hca9goshbchydrzypoz4x4bgni8f X-HE-Tag: 1725296587-897288 X-HE-Meta: U2FsdGVkX1+yZW97Z5bAl5NFSQFz6KqDVLosyojkUASFHQK0W3qJdOoCkfufOxZgolTkFT4SWSmfpIW9DdcUlS93LdLsYlQuEuF63ia97AMK+pgElzMmx9wS+Oe99mN8zYJp3qdCjKyABVLdK/H2dGY6pWPH+0XmcIDpsFeu4r//ClB9P3GGDbrWbgDF0JIXanLcpPyaEc5iLN9a6H1IGtRKoZ+rc5K9xw0gfa8gqBOt4bdfEyWFc7nokE+o2OP/Uuikja6+AEiMC3d1DeWV7R8wRCyqjLyawyAf3CzkOcf1GZoEhGuaFxFNPZlIMuP8j//RAjQj/pZWsdMCSIVTz/NqSWF4RPke69n3a4gNz0hPKYB4ILNgYQZT8r5Fv6KWXqNFM8BkUxe17I8wzxluJ5GCPxC/4LEASg9SkSCx5SduODkpvhfQPq7Megv6PKWeaGC2V40p4EguJ2fRtjNrfI+oVTu2tqYLN/F2/UAF91bGarTrr5kwQGKLD9Ktx2ta/0UCLUhf/pTkT+B3S3wlnNohXEUvMAljKJnwshzTplRxFGcBgl92YcOhog+Kv2yXhDjgcy82mQ8+vdBWZIxE8jdqHh4GGA5+LfROpOqkCM2KzmAkeAPmVuLhwIfQrwzjT+JEtNfuxnX28Pxkx2f5iGpwtWj9u6CjnjV7Yhz/E48l0QgxRDzlYr3qNba8f4fVU6wXU9KMcxC65lteiSMBqFqCGezA3v+OxuUV8w2G4Kto7N2OyB0Y1PJ0Zp1YjvDgGa0TJfCckwL/+IqysUpDjXda6AUo+/YyXgl6zC3a/gv5LTq2tomXcjou7EhC8/ZwiHT2iDnbFd1AdYi2UlPGaNR3xL75OG7v6ffON8e0lDvWPLFCvkmqg4FvJgGEoD6ivfKCmDJ2a5fGwuJHVVhU0at23vw73kd5WbBhfKpMTOwpKpJocC8ALppy5M7xCScP66W8J7uM1td0L3fBG85 0+c5H9NV jqDnr+d1yiNSTc8keMzom6a2PeKKMlaAzChMlpH8Wo/UZxvr9uIY97drjc8TcvrbGsQGfFuC/BXaBjihkMp6OsYKz6Nb5oszxFiXgkAx20NBsCEJnnKO+eHVYabU6E+4acyqo4R7pDavXjK7Ba78qOHaq2gyk+tfPBh3zR8enx6e4lL1aqcqnCvIWTsmCJB0fAAVrnteiB6emKYH1d7IZ/ctkdmf8q71UMYXIkSGwhUbbXsPGhAgv3Z6v82F//41NBoltoraAH9b7VbRKpPJvRtHgPNaKoIB+qUjxFKjE/D7XYdZY2gfb5Vpjie/X8OMmNNB4Kz2KpbptonJVtSpVVyytP1+PlgiRnefGGfQR97oBssNkIGBJBUL78320/2IE3OE2wNK4NMm2aIFC8SG5bjetDaLRjBfA90kY7FxLD1XM9MEEhKxq+7n7O1rrpAVa4n11msJD+4/bW1cbfV9o0x7vbQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000281, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello! > > Hi, > > unrelated to your use case, but something that coud easily save a few cycles > on some system, IMHO. > > Maybe: > > #if NR_CPUS > 1 > static __read_mostly unsigned int nr_vmap_nodes = 1; > static __read_mostly unsigned int vmap_zone_size = 1; > #else > #define nr_vmap_nodes 1 > #define vmap_zone_size 1 > #endif > > So that the compiler can do a better job because some loops can be optimized > away and there is no need to access some memory to get theses values. > > Not sure if such a use case can exist or is of any interest. > > This is valide because of [1] and the #ifdef around the num_possible_cpus() > declaration [2, 3]. > > > Just my 2c. > Thank you, i see your point. -- Uladzislau Rezki