On Wed, Apr 21, 2010 at 08:56:04AM -0500, Gary Altenberg wrote: > I’m working with uClinux on a NOMMU ARM and using BusyBox. I have seen people > in this list talk about NOMMU memory fragmentation issues. I’m just wondering > if I’m going to run into major memory fragmentation problems if I run shell > scripts a lot. I have written a few shell scripts to move files around and > have them running frequently. I see that they seem to spawn children with > vfork or something when I do things like sleep or cp. Does anyone have any > advice about how to approach these issues? Should I try to write applications > to handle these things instead of using shell scripts?
Well if your shell scripts run and terminate (freeing all the ram they used as a result) and no other processes allocate any memory while they run, then you should not have a problem from that. On the other hand if you do something like: launch a process from a startup script and background it launch another process from startup script and background it, while the first one is making memory allocations or calling external scripts and commands etc Then you are likely to end up causing a lot of fragmentation. I did find that making busybox as small as possible in the heap+bss+stack usage made a big difference in how much memory was used and how fragmented things got. In my case my busybox config was using 67KB, but by making a few config changes (switch mv/cp buffer to malloc instead of stack and remove a few unused features), I dropped that to 59KB. Of course 59KB requires a 64KB chunk, while 67KB requires a 128KB chunk in the nommu power of two allocator, so that suddenly makes each busybox command require half as much memory, and hence only need half as big a chunk of memory. Suddenly an 8MB machine was doing very well, where before a shell script piping 4 or 5 commands together could make it run out of ram (in big enough pieces, there were lots of 32 and 64KB chunks left but those were not big enough to be useful). -- Len Sorensen _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
