On 26/08/14 10:13, Josh Berkus wrote:
On 08/22/2014 07:02 AM, Andres Freund wrote:
On 2014-08-21 14:02:26 -0700, Josh Berkus wrote:
On 08/20/2014 07:40 PM, Bruce Momjian wrote:
Not sure how you can make such a blanket statement when so many people
have tested and shown the benefits of hyper-threading.
Actually, I don't know that anyone has posted the benefits of HT.
Link?
There's definitely cases where it can help. But it's highly workload
*and* hardware dependent.
The only cases I've seen where HT can be beneficial is when you have
large numbers of idle connections. Then the idle connections can be
"parked" on the HT virtual cores. However, even in this case I haven't
seen a head-to-head performance comparison.
I've just had a pair of Crucial m550's arrive, so a bit of benchmarking
is in order. The results (below) seem to suggest that HT enabled is
certainly not inhibiting scaling performance for single socket i7's. I
performed several runs (typical results shown below).
Intel i7-4770 3.4 Ghz, 16G
2x Crucial m550
Ubuntu 14.04
Postgres 9.4 beta2
logging_collector = on
max_connections = 600
shared_buffers = 1GB
wal_buffers = 32MB
checkpoint_segments = 128
effective_cache_size = 10GB
pgbench scale = 300
test duration (each) = 600s
db on 1x m550
xlog on 1x m550
clients | tps (HT)| tps (no HT)
--------+----------+-------------
4 | 517 | 520
8 | 1013 | 999
16 | 1938 | 1913
32 | 3574 | 3560
64 | 5873 | 5412
128 | 8351 | 7450
256 | 9426 | 7840
512 | 9357 | 7288
Regards
Mark
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