Re: O(1) scheduler gives big boost to tbench 192

rwhron@earthlink.net
Mon, 20 May 2002 08:46:11 -0400


> On Tue, May 07, 2002 at 04:39:34PM -0700, Robert Love wrote:
> > It is just for pipes we previously used sync, no?

On Tue, 7 May 2002 16:48:57 -0700, Mike Kravetz wrote
> That's the only thing I know of that used it.

> I'd really like to know if there are any real workloads that
> benefited from this feature, rather than just some benchmark.
> I can do some research, but was hoping someone on this list
> might remember. If there is a valid workload, I'll propose
> a patch.

On Mon, 13 May 2002 02:06:31 +0200, J.A. Magallon wrote:
> - Re-introduction of wake_up_sync to make pipes run fast again. No idea
> about this is useful or not, that is the point, to test it

2.4.19-pre8-jam2 showed slightly better performance on the quad Xeon
for most benchmarks with 25-wake_up_sync backed out. However, it's
not clear to me 25-wake_up_sync was proper patch to backout for this
test, as there wasn't a dramatic change in Pipe latency or bandwidth
without it.

There was a > 300% improvement lmbench Pipe bandwidth and latency
comparing pre8-jam2 to pre7-jam6.

Average of 25 lmbench runs on jam2 kernels, 12 on the others:
2.4.19-pre8-jam2-nowuos (backed out 25-wake_up_sync patch)

*Local* Communication latencies in microseconds - smaller is better
AF
kernel Pipe UNIX
----------------------- ----- -----
2.4.19-pre7-jam6 29.51 42.37
2.4.19-pre8 10.73 29.94
2.4.19-pre8-aa2 12.45 29.53
2.4.19-pre8-ac1 35.39 45.59
2.4.19-pre8-jam2 7.70 15.27
2.4.19-pre8-jam2-nowuos 7.74 14.93

*Local* Communication bandwidths in MB/s - bigger is better
AF
kernel Pipe UNIX
----------------------- ------ ------
2.4.19-pre7-jam6 66.41 260.39
2.4.19-pre8 468.57 273.32
2.4.19-pre8-aa2 418.09 273.59
2.4.19-pre8-ac1 110.62 241.06
2.4.19-pre8-jam2 545.66 233.68
2.4.19-pre8-jam2-nowuos 544.57 246.53

The kernel build test, which applies patches through a pipe
and compiles with -pipe didn't reflect an improvement.

kernel average min_time max_time runs notes
2.4.19-pre7-jam6 237.0 235 239 3 All successful
2.4.19-pre8 239.7 238 241 3 All successful
2.4.19-pre8-aa2 237.7 237 238 3 All successful
2.4.19-pre8-ac1 239.3 238 241 3 All successful
2.4.19-pre8-jam2 240.0 238 241 3 All successful
2.4.19-pre8-jam2-nowuos 238.7 236 241 3 All successful

I don't know how much of the kernel build test is dependant on
pipe performance. There is probably a better "real world"
measurement.

On a single processor box, there was an improvement on kernel build
between pre7-jam6 and pre8-jam2. That was only on one sample though.

Xeon page:
http://home.earthlink.net/~rwhron/kernel/bigbox.html

Latest on uniproc:
http://home.earthlink.net/~rwhron/kernel/latest.html

-- 
Randy Hron

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