On Wed, Dec 30, 2015 at 09:00:32AM -0500, Rick Macklem wrote: > Niels de Vos wrote: > > On Tue, Dec 29, 2015 at 08:12:40PM -0500, Rick Macklem wrote: > > > Hi, > > > > > > I'm been playing with the FreeBSD port of GlusterFS and it seems > > > to be working ok. I do notice that the daemons use a lot of CPU, > > > even when there is nothing to do (no volumes started, etc). > > > When I ktrace the daemon, I see a small number of nanosleep() and > > > select() syscalls and lots of poll() syscalls (close to 1000/sec). > > > > > > Looking at libglusterfs/src/event-poll.c, I find: > > > ret = poll(ufds, size, 1); > > > in a loop. The only thing the code seems to do when poll() times > > > out is a call to event_dispatch_poll_resize(). > > > > > > So, is it necessary to call event_dispatch_poll_resize() 1000 times > > > per second? > > > Or is there a way to make event_dispatch_poll_resize() return quickly > > > when there is nothing to do? > > > > I do not think this is critical. A longer timeout should be well > > acceptable. > > > > > I'm guessing that Linux uses the event-epoll stuff instead of event-poll, > > > so it wouldn't exhibit this. Is that correct? > > > > Well, both. most (if not all) Linux builds will use event-poll. But, > > that calls epoll_wait() with a timeout of 1 millisecond as well. > > > Actually, when I look at the 3.7.6 sources in libglusterfs/src/event-epoll.c > I only find one epoll_wait() at line#668: > ret = epoll_wait (event_pool->fd, &event, 1, -1); > so the timeout never happens in this code. > (It does have code after the call to handle the timeout case.) > All it seems to do (if it were to timeout) is adjust the # of threads in the > event-epoll case, so my hunch is that a timeout isn't needed? Oh, yes, indeed, my mistake. > For the event-poll.c case, it calls event_dispatch_poll_size() which looks like > it might add new file descriptors, so someone more familiar with this code would > need to decide if the timeout can be disabled (my hunch is no, but I'm not familiar > with the code). Maybe Shyam (on CC) knows more how event-poll works. He is definitely one of the developers that could explain epoll, and I guess he looked into poll too. Niels > > > Thanks for any information on this, rick > > > ps: I am tempted to just crank the timeout of 1msec up to 10 or 20msec. > > > > Yes, that is probably what I would do too. And have both poll functions > > use the same timeout, have it defined in libglusterfs/src/event.h. We > > could make it a configurable option too, but I do not think it is very > > useful to have. > > > > Could you file a bug and/or send a patch for this? > > > I will try bumping the timeout up in event-poll.c and if it seems to reduce > CPU usage and not cause any obvious grief, I will file a bug report. > > Thanks for your help with this, rick > > > Thanks, > > Niels > >
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