6.8.0.x, 64 bits, and memory profiling
simonmarhaskell at gmail.com
Mon Nov 5 11:16:06 EST 2007
Ketil Malde wrote:
> I'm using heap profiling on AMD64, and I am getting some slightly
> strange results. Running the profiling, 'top' shows about 600Mb in
> use, but the resulting profile shows ~80Mb. Rerunning with -M200M
> results in an out-of-memory error.
> Could it be that the profile is calculated incorrectly for 64bit
It's probably correct. Profiling overheads add 50-100% to the space usage,
which is subtracted from the profile. Copying GC will use about 3x the
live data in normal operation: 2x due to the copying, and an extra 1x to
allocate into, plus there may be some free memory due to fragmentation
(hopefully not much). The +RTS -sstderr will give you an accurate figure
of how much memory GHC's allocator is using.
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