On Fri, Jan 19, 2018 at 1:53 PM, Konstantin Knizhnik < k.knizh...@postgrespro.ru> wrote:
> > > On 19.01.2018 19:28, Pavel Stehule wrote: > > > > When I've been thinking about adding a built-in connection pool, my >>> rough plan was mostly "bgworker doing something like pgbouncer" (that >>> is, listening on a separate port and proxying everything to regular >>> backends). Obviously, that has pros and cons, and probably would not >>> work serve the threading use case well. >>> >> >> And we will get the same problem as with pgbouncer: one process will not >> be able to handle all connections... >> Certainly it is possible to start several such scheduling bgworkers... >> But in any case it is more efficient to multiplex session in backend >> themselves. >> > > pgbouncer hold all time client connect. When we implement the listeners, > then all work can be done by worker processes not by listeners. > > > Sorry, I do not understand your point. > In my case pgbench establish connection to the pgbouncer only once at the > beginning of the test. > And pgbouncer spends all time in context switches (CPU usage is 100% and > it is mostly in kernel space: top of profile are kernel functions). > The same picture will be if instead of pgbouncer you will do such > scheduling in one bgworker. > For the modern systems are not able to perform more than several hundreds > of connection switches per second. > So with single multiplexing thread or process you can not get speed more > than 100k, while at powerful NUMA system it is possible to achieve millions > of TPS. > It is illustrated by the results I have sent in the previous mail: by > spawning 10 instances of pgbouncer I was able to receive 7 times bigger > speed. > I'm sure pgbouncer can be improved. I've seen async code handle millions of packets per second (zmq), pgbouncer shouldn't be radically different.
