I appear to be using huge amounts of CPU time, and I am trying to work out why. The commands I ran and their output are in systime_log at http://urchin.earth.li/~ian/systime/, and all the source and other output is there too. Essentially the program uses more system time than user time according to time (bash built-in, Linux x86), and I'd like to know why (or more precisely I'd like to reduce it, but knowing why seems like a good first move :-) ).

I'm somewhat confused as to why the numbers given by time and strace -c don't match, but nevertheless it looks to me like the time must be due to one or more of:

rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 rt_sigprocmask(SIG_BLOCK, [], [], 8) = 0 --- SIGVTALRM (Virtual timer expired) --- sigreturn() = ? (mask now [])

I'm not sure where to go from here. Any suggestions?

From the strace -c ouput, I'd say the system time isn't being eaten up by system calls and signals. The only other system time sink is page faults and swapping activity (I believe), but from the look of it your program is only using a few MB. What does the output from +RTS -Sstderr look like?

I'm stumped too, but I'm intrigued to know what's going on. Cheers, Simon