Luke Kenneth Casson Leighton wrote:
On Mon, Oct 20, 2014 at 1:53 PM, Howard Chu hyc@symas.com wrote:
My experience from benchmarking OpenLDAP over the years is that mutexes scale only up to a point. When you have threads grabbing the same mutex from across socket boundaries, things go into the toilet. There's no fix for this; that's the nature of inter-socket communication.
argh. ok. so... actually.... accidentally, the design where i used a single LMDB (one env) shared amongst (20 to 30) processes using db_open to create (10 or so) databases would mitigate against that... taking a quick look at mdb.c the mutex lock is done on the env not on the database...
sooo compared to the previous design there would only be a 20/30-to-1 mutex contention whereas previously there were *10 sets* of 20 or 30 to 1 mutexes all competing... and if mutexes use sockets underneath that would explain why the inter-process communication (which also used sockets) was so dreadful.
Note - I was talking about physical CPU sockets, not network sockets.
huh, how about that.
do you happen to have access to a straight 8-core SMP system,
No.
or is it relatively easy to turn off the NUMA architecture?
I can probably use taskset or something similar to restrict a process to a particular set of cores. What exactly do you have in mind?