[Haskell-cafe] Re: Optimizing a high-traffic network architecture

Simon Marlow simonmar at microsoft.com
Thu Jan 5 06:09:45 EST 2006

Joel Reymont wrote:
> My apologies if this has been described somewhere but what is MUT time?

MUTator time, i.e. the time spent doing real work by your program.  (the 
term "mutator" isn't used so much these days, but it comes from the view 
of a functional program as a graph, and the engine that "mutates" or 
"reduces" the graph is called the "mutator".)

> Also, isn't 30% GC a bit high? This is something that totally  surprised 
> me when I first saw it as my program was spending 60-70% on  GC.

It is a little high, yes.  GC time on a 64-bit machine tends to be 
higher because there are twice as many bits to shuffle around.

> Is there a good low % number that should be used as a benchmark?

As a rule of thumb I usually consider >30% to be a bit on the high side, 
it would be time to investigate with profiling and try to reduce 
residency or allocation rate.


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