On Wed, Sep 12, 2018 at 6:18 PM Ben Peart <benpe...@microsoft.com> wrote:
> #ifndef NO_PTHREADS
> nr_threads = git_config_get_index_threads();
> - if (!nr_threads)
> - nr_threads = online_cpus();
> + if (!nr_threads) {
> + cpus = online_cpus();
> + nr_threads = istate->cache_nr / THREAD_COST;
> + if (nr_threads > cpus)
> + nr_threads = cpus;
It seems like overcommitting cpu does reduce time. With this patch
(and a 4 core system), I got
$ test-tool read-cache 100
real 0m36.270s
user 0m54.193s
sys 0m17.346s
if I force nr_threads to 9 (even though cpus is 4)
$ test-tool read-cache 100
real 0m33.592s
user 1m4.230s
sys 0m18.380s
Even though we use more cpus, real time is shorter. I guess these
threads still sleep a bit due to I/O and having more threads than
cores will utilize those idle cycles.
--
Duy
