* Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> wrote: > The throughput of pure mmap with mutex is below vs pure mmap is below: > > % change in performance of the mmap with pthread-mutex vs pure mmap > #threads vanilla all rwsem without optspin > patches > 1 3.0% -1.0% -1.7% > 5 7.2% -26.8% 5.5% > 10 5.2% -10.6% 22.1% > 20 6.8% 16.4% 12.5% > 40 -0.2% 32.7% 0.0% > > So with mutex, the vanilla kernel and the one without optspin both run > faster. This is consistent with what Peter reported. With optspin, the > picture is more mixed, with lower throughput at low to moderate number > of threads and higher throughput with high number of threads. So, going back to your orignal table: > % change in performance of the mmap with pthread-mutex vs pure mmap > #threads vanilla all without optspin > 1 3.0% -1.0% -1.7% > 5 7.2% -26.8% 5.5% > 10 5.2% -10.6% 22.1% > 20 6.8% 16.4% 12.5% > 40 -0.2% 32.7% 0.0% > > In general, vanilla and no-optspin case perform better with > pthread-mutex. For the case with optspin, mmap with pthread-mutex is > worse at low to moderate contention and better at high contention. it appears that 'without optspin' appears to be a pretty good choice - if it wasn't for that '1 thread' number, which, if I correctly assume is the uncontended case, is one of the most common usecases ... How can the single-threaded case get slower? None of the patches should really cause noticeable overhead in the non-contended case. That looks weird. It would also be nice to see the 2, 3, 4 thread numbers - those are the most common contention scenarios in practice - where do we see the first improvement in performance? Also, it would be nice to include a noise/sttdev figure, it's really hard to tell whether -1.7% is statistically significant. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>