barry@pico.math.ucla.edu (Barry Merriman) (03/03/91)
Yes, you definitely need more memory if you plan to use Mathematica extensively. I found this out the hard way: after a day long session on my 8MB + 105MB Slab, M'ma was swapping extensively. A quick check showed it had grown to over 16MB. Time to quit---but I took it to far, trying to squeeze out one last calculation before saving an quiting. My HD went into a thrashing mode, nothing would respond and after a hour I went home, leaving it to thrash and hopefully complete that final calculation via thousands of swaps. No such luck---eventually it logged me out, and left a 40MB swapfile. M'ma defeated the virtual memory, which of course is only as good as your real memory. So, aside from the huge slowdown due to swapping, if you want to avoid these unsightly VM failures, get some more memory. A total of 20MB RAM would appear sufficient for a single user (i.e. add 4 x 4MB). Also, remember you'll need to allow for a bigger swapfile as well on your hard disk. -- Barry Merriman UCLA Dept. of Math UCLA Inst. for Fusion and Plasma Research barry@math.ucla.edu (Internet)
tvz@phoenix.Princeton.EDU (Timothy Van Zandt) (03/05/91)
In article <1991Mar3.055657.3212@math.ucla.edu> barry@pico.math.ucla.edu (Barry Merriman) writes: >to avoid these unsightly VM failures, get some more memory. >A total of 20MB RAM would appear sufficient for a single user >(i.e. add 4 x 4MB). Also, remember you'll need to allow >for a bigger swapfile as well on your hard disk. Why does increasing memory increase the required size of the swap file? I heard this mentioned before, but it seems like the opposite should be true. Tim Van Zandt tvz@princeton.edu
scott@mcs-server.gac.edu (Scott Hess) (03/06/91)
In article <6863@idunno.Princeton.EDU> tvz@phoenix.Princeton.EDU (Timothy Van Zandt) writes: In article <1991Mar3.055657.3212@math.ucla.edu> barry@pico.math.ucla.edu (Barry Merriman) writes: >to avoid these unsightly VM failures, get some more memory. >A total of 20MB RAM would appear sufficient for a single user >(i.e. add 4 x 4MB). Also, remember you'll need to allow >for a bigger swapfile as well on your hard disk. Why does increasing memory increase the required size of the swap file? I heard this mentioned before, but it seems like the opposite should be true. [This may or may not be true for Mach/Unix on the NeXT - it is true for regular Unix, and I'd give odds that it was for Mach/Unix, also] All memory used by processes must have space in the swapfile. This space is allocated when the memory is allocated, needed or not. In this way, you don't have programs run for a couple minutes then die when they are inactive and the swapper attempts to swap some of their data out so that another process can use memory - and there is no room. The generally recommended configuration for swapfiles is to allocate 2x the real memory size for the minimum size of the swapfile (obviously, it can grow to fill the disk it's on, under Mach). You don't have to do this - it's just a recommendation. In general, if you need 20M of memory, you'll probably end up with a 40M swapfile, anyhow. You cannot count on disk space freed up by shrinking the lowater size of the swapfile, because almost certainly you will need it back at some point in the future, anyhow. Later -- scott hess scott@gac.edu Independent NeXT Developer GAC Undergrad <I still speak for nobody> "Tried anarchy, once. Found it had too many constraints . . ." "I smoke the nose Lucifer . . . Bannana, banna."
klingler@triton.unm.edu (David Klingler) (03/11/91)
In article <SCOTT.91Mar5142921@mcs-server.gac.edu> scott@mcs-server.gac.edu (Scott Hess) writes: >In article <6863@idunno.Princeton.EDU> tvz@phoenix.Princeton.EDU (Timothy Van Zandt) writes: > In article <1991Mar3.055657.3212@math.ucla.edu> barry@pico.math.ucla.edu > (Barry Merriman) writes: > > >to avoid these unsightly VM failures, get some more memory. > >A total of 20MB RAM would appear sufficient for a single user > >(i.e. add 4 x 4MB). Also, remember you'll need to allow > >for a bigger swapfile as well on your hard disk. > > Why does increasing memory increase the required size of the swap > file? I heard this mentioned before, but it seems like the opposite > should be true. > >[This may or may not be true for Mach/Unix on the NeXT - it is true > for regular Unix, and I'd give odds that it was for Mach/Unix, also] >All memory used by processes must have space in the swapfile. This >space is allocated when the memory is allocated, needed or not. In >this way, you don't have programs run for a couple minutes then >die when they are inactive and the swapper attempts to swap some of >their data out so that another process can use memory - and there is >no room. > >The generally recommended configuration for swapfiles is to allocate >2x the real memory size for the minimum size of the swapfile (obviously, >it can grow to fill the disk it's on, under Mach). You don't have >to do this - it's just a recommendation. In general, if you need >20M of memory, you'll probably end up with a 40M swapfile, anyhow. >You cannot count on disk space freed up by shrinking the lowater >size of the swapfile, because almost certainly you will need it >back at some point in the future, anyhow. > >Later >-- >scott hess scott@gac.edu >Independent NeXT Developer GAC Undergrad ><I still speak for nobody> >"Tried anarchy, once. Found it had too many constraints . . ." >"I smoke the nose Lucifer . . . Bannana, banna." Okay. I've added another 8 megs. But how do I go about changing my swapfile size? Especially when the bug list in the man entry says that a swapfile cannot be deactivated when in use? I'm beginning to think the fact that I haven't modified my swapfile size is responsible for a few nasty crashes... Dave klingler@triton.unm.edu