----- Original Message ----- > From: "Rick Macklem" <rmacklem@xxxxxxxxxxx> > To: "Jeff Darcy" <jdarcy@xxxxxxxxxx> > Cc: "Raghavendra G" <raghavendra@xxxxxxxxxxx>, "freebsd-fs" <freebsd-fs@xxxxxxxxxxx>, "Hubbard Jordan" > <jkh@xxxxxxxxxxxxx>, "Xavier Hernandez" <xhernandez@xxxxxxxxxx>, "Gluster Devel" <gluster-devel@xxxxxxxxxxx> > Sent: Saturday, January 9, 2016 7:29:59 AM > Subject: Re: FreeBSD port of GlusterFS racks up a lot of CPU usage > > Jeff Darcy wrote: > > > > I don't know anything about gluster's poll implementation so I may > > > > be totally wrong, but would it be possible to use an eventfd (or a > > > > pipe if eventfd is not supported) to signal the need to add more > > > > file descriptors to the poll call ? > > > > > > > > > > > > The poll call should listen on this new fd. When we need to change > > > > the fd list, we should simply write to the eventfd or pipe from > > > > another thread. This will cause the poll call to return and we will > > > > be able to change the fd list without having a short timeout nor > > > > having to decide on any trade-off. > > > > > > > > > Thats a nice idea. Based on my understanding of why timeouts are being > > > used, this approach can work. > > > > The own-thread code which preceded the current poll implementation did > > something similar, using a pipe fd to be woken up for new *outgoing* > > messages. That code still exists, and might provide some insight into > > how to do this for the current poll code. > I took a look at event-poll.c and found something interesting... > - A pipe called "breaker" is already set up by event_pool_new_poll() and > closed by event_pool_destroy_poll(), however it never gets used for > anything. I did a check on history, but couldn't find any information on why it was removed. Can you send this patch to http://review.gluster.org ? We can review and merge the patch over there. If you are not aware, development work flow can be found at: http://www.gluster.org/community/documentation/index.php/Developers > > So, I added a few lines of code that writes a byte to it whenever the list of > file descriptors is changed and read when poll() returns, if its revents is > set. > I also changed the timeout to -1 (infinity) and it seems to work for a > trivial > test. > --> Btw, I also noticed the "changed" variable gets set to 1 on a change, but > never reset to 0. I didn't change this, since it looks "racey". (ie. I > think you could easily get a race between a thread that clears it and one > that adds a new fd.) > > A slightly safer version of the patch would set a long (100msec ??) timeout > instead > of -1. > > Anyhow, I've attached the patch in case anyone would like to try it and will > create a bug report for this after I've had more time to test it. > (I only use a couple of laptops, so my testing will be minimal.) > > Thanks for all the help, rick > > > _______________________________________________ > > freebsd-fs@xxxxxxxxxxx mailing list > > https://lists.freebsd.org/mailman/listinfo/freebsd-fs > > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@xxxxxxxxxxx" > > > _______________________________________________ Gluster-devel mailing list Gluster-devel@xxxxxxxxxxx http://www.gluster.org/mailman/listinfo/gluster-devel
