Date: Sun, 04 May 1997 17:47:17 -0500 From: Alex Nash <nash@mcs.com> To: freebsd-smp@freebsd.org Subject: SMP performance (what am I doing wrong) Message-ID: <336D11F5.2781E494@mcs.com>
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I've just upgraded to 3.0 with SMP support, and have been
pleasantly surprised with the stability of the kernel. However,
I'm having a few problems getting the performance I expected.
Before anyone asks, yes, I do have both CPUs running :)
# sysctl -a | grep smp
kern.smp_active: 2
kern.smp_cpus: 2
Using the old RC5 client we're all so familiar with, I ran a
few benchmarks. Under 2.2 with one processor, I think I was
getting in the low 100,000-110,000 range. Here's what I got
with the SMP kernel (all results are with the system in a
quiescent state):
$ ./client -m
rc5-56-client: Performance testing with 1000000 crypts
rc5-56-client: Complete in 13.298 seconds. (75198.80 keys/sec)
Now with 2 clients:
$ ./client -m & ./client -m;wait
[1] 1425
rc5-56-client: Performance testing with 1000000 crypts
rc5-56-client: Performance testing with 1000000 crypts
rc5-56-client: Complete in 24.969 seconds. (40049.51 keys/sec)
rc5-56-client: Complete in 25.112 seconds. (39821.81 keys/sec)
Ouch! I ran it again and got completely different results:
$ ./client -m & ./client -m;wait
[1] 1451
rc5-56-client: Performance testing with 1000000 crypts
rc5-56-client: Performance testing with 1000000 crypts
rc5-56-client: Complete in 18.588 seconds. (53797.31 keys/sec)
rc5-56-client: Complete in 18.910 seconds. (52881.56 keys/sec)
An interesting thing I saw in top: the cpuidle processes were
at about 20% the entire time the clients were running. How
could that be?
Running it again produced similar results to the last run.
Another benchmark I tried was compiling some software from
work with various make -j options. Again the results were
interesting:
Real User Sys
Single CPU/make -j1 4:38.7 3:20.0 0:57.8
Single CPU/make -j4 4:38.6 3:24.8 0:56.8
Dual CPU/make -j1 5:31.5 2:41.0 3:19.9
Dual CPU/make -j4 4:11.6 4:16.9 2:55.9
Dual CPU/make -j8 4:21.0 4:16.1 2:59.9
Am I missing kernel compile options? I've used SMP, and
APIC_IO.
If anyone has any clues as to what's going on, I'd really
appreciate hearing them.
Thanks.
Alex
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