Stephen Frost <sfrost@xxxxxxxxxxx> wrote: > Maxim Boguk (maxim.boguk@xxxxxxxxx) wrote: >>> 6. does PostgreSQL support NUMA on Intel based X64 servers and >>> does it support Hyper-Threading ? >> >> No NUMA support. Yes PostgreSQL will work on HT enabled servers >> (will it be efficient - depend on workload and CPU type). > > PostgreSQL doesn't need to directly support NUMA- the Linux > kernel does. As for if we do anything special when running in a > NUMA environment, no, not at this time. Ditto with > hyper-threading. Since each connection creates its own backend process, each connection's local data in a NUMA environment tends to be allocated from a "nearby" memory segment. So NUMA for a connection's private memory is very efficiently handled by default. Where an issue could possibly arise is in the shared memory, used for the page buffers and interprocess communication (such as locks). If allocations for that become unbalanced, the CPU controlling a heavily used memory segment could become a bottleneck. I did some investigation into NUMA issues with PostgreSQL after seeing some NUMA performance issues on a machine with four memory segments and a database which fit in about 1/4 of the machine's RAM *and* the user pre-warmed the cache using a single process. I found that by programming PostgreSQL to use interleaved mode for shared memory *and* using an OS cpuset to interleave OS buffers and cache I was able to get a consistent 2% to 3% performance increase and prevent occasional (rare) "spikes" of bad performance. Almost all of that was gained just by using the OS cpuset feature (which does not require any change to PostgreSQL to do), so we didn't make any change to PostgreSQL -- a sysadmin can manage interleaved buffer allocation pretty easily if they need to. If you were able to find a situation where NUMA issues within PostgreSQL caused even a 1% hit, we could always revisit the issue. -- Kevin Grittner EDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
