RTS option -A affecting cpu-core usage?
Daniel Trstenjak
daniel.trstenjak
Tue Oct 8 20:02:47 UTC 2013
Hi all,
I played around with a parallel algorithm and tried to get the GC time
down by specifying the RTS option '-A'.
But if I'm specifying '-A' than also the usage of the cpu-cores seems to
change. Without '-A' I'm getting a total cpu-core usage of '4.44s',
with '-A' I'm getting only '1.67s'.
Any ideas?
Greetings,
Daniel
Without '-A':
-------------
dan at machine ~> ghc-mod-dev find showWindows +RTS -s -N4
XMonad.Util.XUtils
980,770,296 bytes allocated in the heap
552,122,168 bytes copied during GC
163,683,152 bytes maximum residency (11 sample(s))
4,369,800 bytes maximum slop
280 MB total memory in use (0 MB lost due to fragmentation)
Tot time (elapsed) Avg pause Max pause
Gen 0 1690 colls, 1690 par 2.45s 0.66s 0.0004s 0.0024s
Gen 1 11 colls, 10 par 0.98s 0.26s 0.0239s 0.1022s
Parallel GC work balance: 18.06% (serial 0%, perfect 100%)
TASKS: 6 (1 bound, 5 peak workers (5 total), using -N4)
SPARKS: 1025 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 1025 fizzled)
INIT time 0.00s ( 0.00s elapsed)
MUT time 0.99s ( 0.83s elapsed)
GC time 3.43s ( 0.93s elapsed)
EXIT time 0.02s ( 0.02s elapsed)
Total time 4.44s ( 1.78s elapsed)
Alloc rate 995,571,064 bytes per MUT second
Productivity 22.7% of total user, 56.5% of total elapsed
gc_alloc_block_sync: 53552
whitehole_spin: 0
gen[0].sync: 75
gen[1].sync: 23678
With '-A':
----------
dan at machine ~> ghc-mod-dev find showWindows +RTS -s -N4 -A500m
XMonad.Util.XUtils
979,761,872 bytes allocated in the heap
94,043,424 bytes copied during GC
118,609,784 bytes maximum residency (2 sample(s))
2,844,808 bytes maximum slop
2196 MB total memory in use (0 MB lost due to fragmentati
Tot time (elapsed) Avg pause Ma
Gen 0 0 colls, 0 par 0.00s 0.00s 0.0000s
Gen 1 2 colls, 1 par 0.47s 0.18s 0.0878s
Parallel GC work balance: 57.02% (serial 0%, perfect 100%)
TASKS: 6 (1 bound, 5 peak workers (5 total), using -N4)
SPARKS: 1025 (616 converted, 0 overflowed, 0 dud, 0 GC'd, 409 fizzl
INIT time 0.02s ( 0.02s elapsed)
MUT time 1.16s ( 1.16s elapsed)
GC time 0.47s ( 0.18s elapsed)
EXIT time 0.02s ( 0.02s elapsed)
Total time 1.67s ( 1.38s elapsed)
Alloc rate 844,914,346 bytes per MUT second
Productivity 70.8% of total user, 85.9% of total elapsed
gc_alloc_block_sync: 33458
whitehole_spin: 0
gen[0].sync: 5372
gen[1].sync: 0
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