[Python-Dev] big performance hit in the past few days

Wed, 3 Apr 2002 18:33:53 -0600

After Guido checked in the bool() stuff I cvs up'd and rebuilt. A few days
ago I spent some time trying to quantify the effect of changes to
SMALL_REQUEST_THRESHOLD on pymalloc performance. The "benchmark" consists
of using the compiler package to compile Lib/*.py and three runs of the
pystone main program with LOOPS set to 100000 (10x the usual value).
On March 31, I got the following output with and without pymalloc enabled
and a SMALL_REQUEST_THRESHOLD of 256:
 w/ pymalloc
 Pystone(1.1) time for 100000 passes = 16.81
 This machine benchmarks at 5948.84 pystones/second
 Pystone(1.1) time for 100000 passes = 16.82
 This machine benchmarks at 5945.3 pystones/second
 Pystone(1.1) time for 100000 passes = 16.83
 This machine benchmarks at 5941.77 pystones/second
 243.84user 0.23system 4:12.73elapsed 96%CPU (0avgtext+0avgdata 0maxresident)k
 0inputs+0outputs (402major+4432minor)pagefaults 0swaps
 w/o pymalloc
 Pystone(1.1) time for 100000 passes = 17.66
 This machine benchmarks at 5662.51 pystones/second
 Pystone(1.1) time for 100000 passes = 17.67
 This machine benchmarks at 5659.31 pystones/second
 Pystone(1.1) time for 100000 passes = 17.66
 This machine benchmarks at 5662.51 pystones/second
 277.88user 0.21system 4:48.10elapsed 96%CPU (0avgtext+0avgdata 0maxresident)k
 0inputs+0outputs (400major+3943minor)pagefaults 0swaps
Running the same benchmark just now I got:
 w/ pymalloc
 Pystone(1.1) time for 100000 passes = 25.1
 This machine benchmarks at 3984.06 pystones/second
 Pystone(1.1) time for 100000 passes = 24.99
 This machine benchmarks at 4001.6 pystones/second
 Pystone(1.1) time for 100000 passes = 24.74
 This machine benchmarks at 4042.04 pystones/second
 352.33user 0.97system 6:51.40elapsed 85%CPU (0avgtext+0avgdata 0maxresident)k
 0inputs+0outputs (499major+4181minor)pagefaults 0swaps
 w/o pymalloc
 Pystone(1.1) time for 100000 passes = 25.01
 This machine benchmarks at 3998.4 pystones/second
 Pystone(1.1) time for 100000 passes = 25.09
 This machine benchmarks at 3985.65 pystones/second
 Pystone(1.1) time for 100000 passes = 25.18
 This machine benchmarks at 3971.41 pystones/second
 374.38user 0.26system 6:37.71elapsed 94%CPU (0avgtext+0avgdata 0maxresident)k
 0inputs+0outputs (401major+3950minor)pagefaults 0swaps
All files were compiled using gcc 3.0.4 with OPT set at -O3.
The fact that the tests slowed down dramatically both with and without
pymalloc enabled suggests that recent changes to obmalloc are not to blame.
(On March 31, I was using obmalloc.c 2.24. Today I'm using 2.27.)
Any thoughts on the possible cause? It's tough to casually suggest a
particular culprit because the bool() stuff touched a lot of files. I can't
simply identify a few files that changed in the past few days. I count 66
.c[ch] files new or updated since mid-afternoon April 1.
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