On Wed, 06 Jan 2010 22:39:09 +0100 Carsten Emde <Carsten.Emde@xxxxxxxxx> wrote: > I know that there are quite a few people out there who get furious, if > someone breaks backward compatibility - especially in things that are > used for automatic testing. Cyclictest is such a thing. > > In addition, I would propose to consider not only affinity but also the > number of threads. If, for example, someone specifies -a -t5 on a > four-way machine, then it may not make sense to use the same priority > and the same interval on all threads. If any, the new feature would only > make sense in cases where both the -a and the -t option do not have an > argument so the number of threads matches the number of CPUs and every > thread runs on its own CPU. Another pitfall is hyperthreading in which > case it may be desired to have as many threads at the same priority as > real CPUs rather than as available hyperthreads. > > Here is my proposal: > Do not change the meaning of existing options. Introduce a new option > that is mutual exclusive with the -a, the -t and the -d option. This new > option does the same as -a and -t and -d0 and sets the same priority to > all threads. How about that? > Ugh, I truly *hate* adding options. Do you know that cyclictest is halfway to having as many options as 'ls'? That being said, I had forgotten that you can provide a list of cpus to -a (as well as -t) so my quick hack really isn't as safe as I first thought it would be. How about if we create the -S/--smp option that takes no arguments and causes -a, -t and -d to be ignored (with a warning). This option would create one thread per cpu, each thread pinned to it's corresponding cpu, all with the same sampling interval (i.e. -d0) and the same priority? Clark
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