On Fri, May 02, 2025 at 08:51:22AM -0700, Stephen Hemminger wrote: > On Fri, 2 May 2025 16:11:31 +0100 > Bruce Richardson <bruce.richard...@intel.com> 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 <bruce.richard...@intel.com> > > 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: > > <cpu number>,...,<cpu number> > or > > <cpu number>-<cpu number> (must be a positive range in ascending order) > or a mixture > > <cpu number>,...,<cpu number>-<cpu number> >
This we already support. > 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: > > <cpu number>-<cpu number>:<used size>/<group size> > 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(). > Those would be good/interesting extensions to have, if someone wants to add them to EAL. Hopefully after this patchset, adding them should be easier as I think we should only have one place in EAL where we parse groups like that: "eal_parse_set()" function. /Bruce
