schock@cpsc.ucalgary.ca (Craig Schock) (03/01/90)
Last week, our swapfile decided to grow to 41 megs (from 21 megs). The reason it did this hasn't yet been determined, but this occurrance made me come up with some way of shrinking the file. I rebooted the system (single user) and I killed off some of the unnecessary processes. I then executed: mkfile 20M /private/vm/swapfile and this seemed to do the trick. What I want to know is ... Is there an EASIER way to bring the swapfile back down to size? Since we are on a 330 Meg HD with only 58 Megs free a jump in the size of the swapfile from 21 megs to 41 megs can cause some problems. Most VM systems I've worked with don't have a "growing" swapfile so this little incident came as a little of a shock. Thanks in advance ======================================================================== Craig Schock schock@cpsc.UCalgary.CA University of Calgary (More reliable ->) schock@flip.cpsc.UCalgary.CA ========================================================================
eps@toaster.SFSU.EDU (Eric P. Scott) (03/01/90)
I don't have an answer for you, but I did get to see what happens when you run out of disk space. This was on a machine that only had a single 660MB drive at the time. The swap file grew to 71 megabytes. It was really weird doing a df and seeing the filesystem 105% full. Needless to say, the machine was pretty much unusable. There were a whole bunch of mach: IO error on pageout: error = 28. mach: vnode_pageout: failed! messages. (I love it: hey! we're out of disk space! what should we do? let's note it in a log file!) The swapfile did shrink a little when the cause went away, but not by a useful amount. Rebooting left about 35 MB free according to df. The culprit: one user, telnetting in, running one program: Mathematica. There aren't many things with such an insatiable appetite for virtual memory--this guy wanted 51 megabytes. I wish I had, say, 48MB RAM in 4MB SIMMs for the memory pigs. (This really makes me wonder about the wisdom of putting only 40MB for swap+/tmp in each of the formerly diskless workstations... Doesn't seem like enough for people who want to do real work.) Interestingly enough, in its present configuration, the machine rarely seems to get "slow" even with its mere 68030--it runs out of process slots before horsepower. Not that I wouldn't mind seeing a faster processor (especially when printing). Still, nothing helps like having enough RAM. You can tell when the machine is paging because the performance loss is so noticeable. -=EPS=-
wilson@mit-amt.MEDIA.MIT.EDU (Wilson Chan) (03/01/90)
In article <2558@cs-spool.calgary.UUCP> schock@cpsc.ucalgary.ca (Craig Schock) writes: [stuff deleted] > What I want to know is ... Is there an EASIER way to bring >the swapfile back down to size? Since we are on a 330 Meg HD with only >58 Megs free a jump in the size of the swapfile from 21 megs to 41 megs >can cause some problems. Most VM systems I've worked with don't have a >"growing" swapfile so this little incident came as a little of a shock. > >Thanks in advance > >======================================================================== >Craig Schock schock@cpsc.UCalgary.CA >University of Calgary (More reliable ->) schock@flip.cpsc.UCalgary.CA >======================================================================== The file, /etc/swaptab, controls the swapfile size. Here's the original file: /private/vm/swapfile lowat=20971520 # 20 Meg low water mark The OS will "attempt" to shrink the swapfile down to lowat. Similarly, you can add a hiwat entry which tells the OS not to grow infinitely big. I think the keyword here is "attempt". My swapfile stays at 20Meg even when I set the lowat to 16Meg and only a Terminal is running. --wilson
mic@ut-emx.UUCP (Mic Kaczmarczik) (03/02/90)
In article <2558@cs-spool.calgary.UUCP> schock@cpsc.ucalgary.ca (Craig Schock) writes: > > Last week, our swapfile decided to grow to 41 megs (from 21 megs). >The reason it did this hasn't yet been determined, but this occurrance >made me come up with some way of shrinking the file. I rebooted the >system (single user) and I killed off some of the unnecessary processes. >I then executed: > > mkfile 20M /private/vm/swapfile > >and this seemed to do the trick. I think this is done automatically on bootup, but I haven't checked lately... > What I want to know is ... Is there an EASIER way to bring >the swapfile back down to size? Since we are on a 330 Meg HD with only >58 Megs free a jump in the size of the swapfile from 21 megs to 41 megs >can cause some problems. Most VM systems I've worked with don't have a >"growing" swapfile so this little incident came as a little of a shock. I don't think there is an easy way to reduce the swapfile size. In my experience, once the swapfile has filled up the disk, about the only thing to do is reboot the system. However, I have been able to *limit* the growth of the swapfile by setting the hiwat parameter in /etc/swaptab; the one we're using on our consulting cube is: # # /etc/swaptab # /private/vm/swapfile lowat=20971520,hiwat=62914560 # 20 Meg low water mark This limits the size of the swapfile to around 60 meg, which will hopefully be enough for this particular cube (its swapfile seems to grow to about 37M after a day or so of operation, so there's plenty of room left). The swaptab man page has more details on the other settings that are available. --mic-- -- Mic Kaczmarczik mic@emx.utexas.edu (Internet) Unix/VMS/Cyber Services mic@utaivc (BITNET) UT Austin Computation Center ...!cs.utexas.edu!ut-emx!mic (UUCP) COM 1/UT Austin/Austin TX 78712 ``Good tea. Nice house.'' -- Worf Please direct consulting questions to gripe@{emx,ix2,ccwf,iv1} as appropriate.
smithw@physc1.byu.edu (03/02/90)
eps@sutro.SFSU.EDU (Eric P. Scott) writes: >The swapfile grew to 71 megabytes I frequently run Mathematica stuff that takes upward of 100MB of swap and the system is virtually dead until I can reboot. ('course I only have an OD only system with the fancy files stripped off). Somebody (Avie?) from NeXT explained why the swapfile grows like this (never shrinks until reboot) last fall. It's probably on the archives somewhere. I have 16 meg ram and things still crawl when I open a big Mathematica file. "Serious" Mathematica stuff is just plain slow on the NeXT. I'm still hoping for Maple with a good NeXT front end.