Re: [tbench regression fixes]: digging out smelly deadmen.

Mike Galbraith
2008-10-25T06:54:00Z

On Sat, 2008-10-25 at 07:58 +0200, Mike Galbraith wrote:
> On Fri, 2008-10-24 at 22:16 -0700, David Miller wrote:

> > If not, please bisect this.
>
> (oh my <fword> gawd:)
>
> I spent long day manweeks trying to bisect and whatnot. It's immune to
> my feeble efforts, and my git-foo.

but..

(tbench/netperf numbers were tested with gcc-4.1 at this time in log, I
went back and re-measured ring-test because I switched compilers)

2.6.22.19-up
ring-test - 1.204 us/cycle = 830 KHz (gcc-4.1)
ring-test - doorstop (gcc-4.3)
netperf - 147798.56 rr/s = 295 KHz (hmm, a bit unstable, 140K..147K rr/s)
tbench - 374.573 MB/sec

2.6.22.19-cfs-v24.1-up
ring-test - 1.098 us/cycle = 910 KHz (gcc-4.1)
ring-test - doorstop (gcc-4.3)
netperf - 140039.03 rr/s = 280 KHz = 3.57us - 1.10us sched = 2.47us/packet network
tbench - 364.191 MB/sec

2.6.23.17-up
ring-test - 1.252 us/cycle = 798 KHz (gcc-4.1)
ring-test - 1.235 us/cycle = 809 KHz (gcc-4.3)
netperf - 123736.40 rr/s = 247 KHz sb 268 KHZ / 134336.37 rr/s
tbench - 355.906 MB/sec

2.6.23.17-cfs-v24.1-up
ring-test - 1.100 us/cycle = 909 KHz (gcc-4.1)
ring-test - 1.074 us/cycle = 931 KHz (gcc-4.3)
netperf - 135847.14 rr/s = 271 KHz sb 280 KHz / 140039.03 rr/s
tbench - 364.511 MB/sec

2.6.24.7-up
ring-test - 1.100 us/cycle = 909 KHz (gcc-4.1)
ring-test - 1.068 us/cycle = 936 KHz (gcc-4.3)
netperf - 122300.66 rr/s = 244 KHz sb 280 KHz / 140039.03 rr/s
tbench - 341.523 MB/sec

2.6.25.17-up
ring-test - 1.163 us/cycle = 859 KHz (gcc-4.1)
ring-test - 1.129 us/cycle = 885 KHz (gcc-4.3)
netperf - 132102.70 rr/s = 264 KHz sb 275 KHz / 137627.30 rr/s
tbench - 361.71 MB/sec

..in 25, something happened that dropped my max context switch rate from
~930 KHz to ~885 KHz. Maybe I'll have better luck trying to find that.
Added to to-do list. Benchmark mysteries I'm going to have to leave
alone, they've kicked my little butt quite thoroughly ;-)

-Mike