Re: What is the PREEMPTION option good for?

Robert Watson wrote:


They're independent twiddles, and can be frobbed separately. If you can
easily measure performance in the different configurations, seeing a
table of permutations and results would be very nice to see what happens
:-).

Ok, this is what I found:

- ipiwakeup doesn't produce differences as calculated by ministat
- turning off preemption produces visible differences, which are
calculated by ministat to be upto 10%.

x nopreempt+ipiwakeup
+ preempt+ipiwakeup
+--------------------------------------------------------------------------+
|+ + + + x x xx xx x|
| |___________A__M________| |______MA_______| |
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 7 99.92 104.19 101.48 101.78429 1.4606717
+ 4 90.5 95.78 94.12 93.53 2.2081365
Difference at 95.0% confidence
-8.25429 +/- 2.4751
-8.10959% +/- 2.43172%
(Student's t, pooled s = 1.74576)


Sorry about the small number of samples - these are collected from the
system in the same state and product version (the machine was otherwise
idle, etc.), but the difference is always present - I've run simpler
benchmarks every few days since the discussion started and it's there.

This is on a low-end dual core Xeon (i.e. one socket, two cores, no HT),
enough RAM not to swap, requests/second with high concurrency on a web
application that does a lot of IPC to database & cache engines through
both TCP/localhost and unix sockets.

_______________________________________________
freebsd-arch@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-arch
To unsubscribe, send any mail to "freebsd-arch-unsubscribe@xxxxxxxxxxx"