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>>> + unsigned int max_cids; >>> unsigned int nr_cpus_allowed; >>> + unsigned int users; >> >> I suspect this reintroduces false-sharing between the "users" >> and "lock" fields (updated every time a thread is forked/exits) >> and load of the pcpu pointer which is pretty much immutable. >> This will slow down accesses to the percpu data in the scheduler >> fast path. > > At this point yes, but when all bits are in place then the lock fields > end up in a different cache line. > > The false sharing issue vs. *pcpu and max_cids is minor, but I can move > the low frequency modified members past the work, so it does not matter > at all. The work stuff is rarely used, so there is no point to worry > about the occasional cache line contention on that. If we have alignment requirements on fields that matter for performance, I recommend using __cacheline_group_{begin,end}_aligned() to make this explicit. See include/linux/cache.h. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com