On Mon, Jul 01, 2013 at 04:48:51PM +0200, Borislav Petkov wrote:
> And yes, this way we don't see the speedup - numbers are almost the
> same. Now on to find out why do I see a speedup with my way of running
> the trace.
Ok, I think I know what happens:
When I do:
perf stat --repeat 10 -a --sync --pre 'make -s clean; echo 1 >
/proc/sys/vm/drop_caches' make -s -j64 bzImage
I get:
Performance counter stats for 'make -s -j64 bzImage' (10 runs):
961485.910628 task-clock # 7.996 CPUs utilized
( +- 0.13% ) [100.00%]
603,572 context-switches # 0.628 K/sec
( +- 0.30% ) [100.00%]
33,044 cpu-migrations # 0.034 K/sec
( +- 0.42% ) [100.00%]
25,450,364 page-faults # 0.026 M/sec
( +- 0.00% )
3,143,626,158,370 cycles # 3.270 GHz
( +- 0.12% ) [83.38%]
2,405,039,723,306 stalled-cycles-frontend # 76.51% frontend cycles idle
( +- 0.09% ) [83.25%]
1,844,508,780,556 stalled-cycles-backend # 58.67% backend cycles idle
( +- 0.19% ) [66.75%]
1,799,457,879,494 instructions # 0.57 insns per cycle
# 1.34 stalled cycles per insn
( +- 0.15% ) [83.36%]
403,458,465,170 branches # 419.620 M/sec
( +- 0.06% ) [83.38%]
17,545,329,408 branch-misses # 4.35% of all branches
( +- 0.11% ) [83.25%]
120.239128672 seconds time elapsed
( +- 0.13% )
VS when I do
perf stat --repeat 10 -a --sync ../build-kernel.sh
where the script contains the same commands:
$ cat ../build-kernel.sh
#!/bin/bash
make -s clean
echo 1 > /proc/sys/vm/drop_caches
make -s -j64 bzImage
$
I get:
Performance counter stats for '../build-kernel.sh' (10 runs):
1032358.179282 task-clock # 7.996 CPUs utilized
( +- 0.09% ) [100.00%]
635,967 context-switches # 0.616 K/sec
( +- 0.15% ) [100.00%]
37,220 cpu-migrations # 0.036 K/sec
( +- 0.27% ) [100.00%]
26,005,286 page-faults # 0.025 M/sec
( +- 0.00% )
3,164,022,396,373 cycles # 3.065 GHz
( +- 0.10% ) [83.37%]
2,434,722,583,577 stalled-cycles-frontend # 76.95% frontend cycles idle
( +- 0.11% ) [83.34%]
1,865,760,946,076 stalled-cycles-backend # 58.97% backend cycles idle
( +- 0.18% ) [66.76%]
1,810,237,888,844 instructions # 0.57 insns per cycle
# 1.34 stalled cycles per insn
( +- 0.10% ) [83.40%]
406,259,324,254 branches # 393.526 M/sec
( +- 0.12% ) [83.32%]
17,610,395,405 branch-misses # 4.33% of all branches
( +- 0.09% ) [83.21%]
129.102139999 seconds time elapsed
( +- 0.09% )
The difference is, in the second case, we're tracing those two also:
make -s clean
echo 1 > /proc/sys/vm/drop_caches
which could be responsible for the variance in timings. I'll run those
tomorrow to confirm.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
