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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-74058dc4641sm1794686b3a.66.2025.05.02.08.51.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 May 2025 08:51:24 -0700 (PDT) Date: Fri, 2 May 2025 08:51:22 -0700 From: Stephen Hemminger To: Bruce Richardson Cc: dev@dpdk.org, david.marchand@redhat.com, mb@smartsharesystems.com Subject: Re: [PATCH v3 1/4] eal: deprecate old coremask-based EAL parameters Message-ID: <20250502085122.2e9db643@hermes.local> In-Reply-To: <20250502151134.536799-2-bruce.richardson@intel.com> References: <20250313113829.1480907-1-bruce.richardson@intel.com> <20250502151134.536799-1-bruce.richardson@intel.com> <20250502151134.536799-2-bruce.richardson@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Fri, 2 May 2025 16:11:31 +0100 Bruce Richardson wrote: > As the number of cores/cpus on platforms has increased over the years, > the use of coremasks rather than core-lists for identifying DPDK cores > has become more and more unwieldy. At this point, let's deprecate the > coremask-based EAL parameters for future removal, and point users to the > core-list based versions instead. > > Signed-off-by: Bruce Richardson Agree. There are some more syntax options on Linux kernel command line: https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.rst#cpu-lists cpu lists Some kernel parameters take a list of CPUs as a value, e.g. isolcpus, nohz_full, irqaffinity, rcu_nocbs. The format of this list is: ,..., or - (must be a positive range in ascending order) or a mixture ,...,- Note that for the special case of a range one can split the range into equal sized groups and for each group use some amount from the beginning of that group: -:/ For example one can add to the command line following parameter: isolcpus=1,2,10-20,100-2000:2/25 where the final item represents CPUs 100,101,125,126,150,151,... The value "N" can be used to represent the numerically last CPU on the system, i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system. Keep in mind that "N" is dynamic, so if system changes cause the bitmap width to change, such as less cores in the CPU list, then N and any ranges using N will also change. Use the same on a small 4 core system, and "16-N" becomes "16-3" and now the same boot input will be flagged as invalid (start > end). The special case-tolerant group name "all" has a meaning of selecting all CPUs, so that "nohz_full=all" is the equivalent of "nohz_full=0-N". The semantics of "N" and "all" is supported on a level of bitmaps and holds for all users of bitmap_parselist().