On 09 September 2005 15:58, Niels wrote:
Bulat Ziganshin wrote:
i don't know what value shows the -xc oprion, but memory usage in ghc-compiled program are increased because by default used "copying" garbage collection algorithm. using option "+RTS -c" will significantly reduce memory usage, which will make program faster if it currently needs swapping. you can also force, for example, using of compacting algorithm when memory usage grows more than 200 mb with options "+RTS -M1G -c20". see "4.14.2. RTS options to control the garbage collector" in ghc docs for details running the profilingbinary (that was compiled with -prof -auto-all) with the -c option resulted in;
top: showing a max of 161mb memory usage profiled-graph: showing a peak at a little more than 80mb
i guess these results are more or less normal? It does however mean that my datastructures are pretty harsh on the garbage collector, doesnt it?
The difference between the residency displayed by the heap profiler and the actual memory residency can be attributed to several factors (some of which have already been mentioned, I thought I'd list them for completeness): - overhead of profiling itself, which currently runs at 2 extra words per heap object. At a guess, that probably results in about a 30% overhead. - generational garbage collection. A major GC in the standard copying collector will usually require 3L bytes of memory, where L is the amount of live data. This is because by default (see the +RTS -F option) we allow the old generation to grow to twice its size (2L) before collecting it, and we require additionally L bytes to copy the live data into. When using compacting collection, this is reduced to 2L, and can further be reduced by tweaking the -F option. Additionally the allocation area (generation 0) takes 512Kb by default. - The stack isn't counted in the heap profile by default. See the +RTS -xt option. - The program text itself, the C stack, any non-heap data (eg. data allocated by foreign libraries, and data allocated by the RTS), and mmap()'d memory are not counted in the heap profile. Cheers, Simon