hi Xavi,
Meet Manoj from
performance team Redhat. He has been testing EC performance in his stretch
clusters. He found some interesting things we would like to share with
you.
1) When we perform multiple streams of big file
writes(12 parallel dds I think) he found one thread to be always hot
(99%CPU always). He was asking me if fuse_reader thread does any extra
processing in EC compared to replicate. Initially I thought it would
just lock and epoll threads will perform the encoding but later realized
that once we have the lock and version details, next writes on the file
would be encoded in the same thread that comes to EC. write-behind
could play a role and make the writes come to EC in an epoll thread but
we saw consistently there was just one thread that is hot. Not multiple
threads. We will be able to confirm this in tomorrow's testing.
2)
This is one more thing Raghavendra G found, that our current
implementation of epoll doesn't let other epoll threads pick messages
from a socket while one thread is processing one message from that
socket. In EC's case that can be encoding of the write/decoding read.
This will not let replies of operations on different files to be
processed in parallel. He thinks this can be fixed for 3.9.
Manoj
will be raising a bug to gather all his findings. I just wanted to
introduce him and let you know the interesting things he is finding
before you see the bug :-).
--
_______________________________________________
Gluster-devel mailing list
Gluster-devel@xxxxxxxxxxx
http://www.gluster.org/mailman/listinfo/gluster-devel
