simpsong@NCoast.ORG (Gregory R. Simpson @ The North Coast) (11/06/90)
Hello, the Subject line pretty much sums it up. I'm using a network of DecStation 3100's and DecStation 5000's to do ray tracing simulations that are very memory intensive. I automatically parallel process the job across the entire network, but in order to do so I have to: rsh node /etc/pstat -s | tail -1 | awk ... on all my nodes to determine if there is enough virtual memory available on the machine to kick off the job... I'd like to write a simple vm_check program that returns nothing except the amount of swap remaining... (which is all I'm interested in... I tried man -k mem, swap, get, and I scrolled through xman with no success... Any hints, code segements, include files to look at etc. would be appreciated... Thanks, Greg -- Gregory R. Simpson GE Lighting (216)-266-6506 simpsong@ltd.ge.com or uunet!crd.ge.com!ltd.decnet!simpsong
mogul@wrl.dec.com (Jeffrey Mogul) (11/07/90)
In article <1990Nov6.033516.18772@NCoast.ORG> simpsong@NCoast.ORG (Gregory R. Simpson @ The North Coast) writes: >I'd like to write a simple vm_check program that returns >nothing except the amount of swap remaining... (which is >all I'm interested in... As you might have guessed from the output of /etc/pstat -s, there isn't simple value stored in the kernel that says "this much swap space is in use"; rather, pstat grovels through kernel data structures counting things up, and computes a total through a fairly hairy computation. I counted over 160 lines in pstat just to do what you're asking for. Since the Ultrix version of pstat.c carries the usual Digital/AT&T copyright, I can't post that on the net. If you get a 4.2BSD source tape, I suspect that the code to do this calculation hasn't changed all that much, so perhaps starting with that version of pstat.c, you can create a program to do what you want. -Jeff
alan@shodha.enet.dec.com ( Alan's Home for Wayward Notes File.) (11/07/90)
In article <1990Nov7.015529.15623@wrl.dec.com>, mogul@wrl.dec.com (Jeffrey Mogul) writes: > In article <1990Nov6.033516.18772@NCoast.ORG> simpsong@NCoast.ORG (Gregory R. Simpson @ The North Coast) writes: > >I'd like to write a simple vm_check program that returns > >nothing except the amount of swap remaining... (which is > >all I'm interested in... > > As you might have guessed from the output of /etc/pstat -s, > there isn't simple value stored in the kernel that says "this > much swap space is in use"; rather, pstat grovels through > kernel data structures counting things up, and computes > a total through a fairly hairy computation. I counted over > 160 lines in pstat just to do what you're asking for. Actually it depends on what version of ULTRIX you're running. In V3.1 and earlier. It's the really hairy stuff that Jeff mentioned. In V4.0 there is a data structure called "swapu" that has how much is being used for various things. The amount free is just the total - the amount used. You can get total from adding amount indicated in the "swdevt" table. > > Since the Ultrix version of pstat.c carries the usual Digital/AT&T > copyright, I can't post that on the net. If you get a 4.2BSD > source tape, I suspect that the code to do this calculation hasn't > changed all that much, so perhaps starting with that version of > pstat.c, you can create a program to do what you want. > In general such things look something like: /* * Correctly dealing with errors, counting up the amount of * page/swap space and getting the units right is left as an * exercise to the reader. */ #include <sys/types.h> #include <sys/file.h> #include <sys/dmap.h> #include <nlist.h> void exit(), nlist() ; off_t lseek() ; struct nlist nl[] = { { "_swapu" }, #define NM_SWAPU 0 { 0 }, }; main() { register rc, fd ; struct swapu_t data ; nlist("/vmunix", nl) ; if((fd = open("/dev/kmem", O_RDONLY)) == -1 ) exit(-1) ; if( lseek(fd, (off_t)nl[NM_SWAPU].n_value, L_SET) == -1 ) exit(-1) ; if( read(fd, (char *)&data, sizeof(data)) == -1 ) exit(-1) ; printf("%d\n", data.total_used) ; printf("%d\n", data.wasted) ; if( close(fd) == -1 ) exit(-1) ; return 0 ; } You may season to taste. > -Jeff -- Alan Rollow alan@nabeth.enet.dec.com
karrer@ethz.UUCP (Andreas Karrer) (11/07/90)
alan@shodha.enet.dec.com ( Alan's Home for Wayward Notes File.) writes: >In article <1990Nov7.015529.15623@wrl.dec.com>, mogul@wrl.dec.com (Jeffrey Mogul) writes: >> In article <1990Nov6.033516.18772@NCoast.ORG> simpsong@NCoast.ORG (Gregory R. Simpson @ The North Coast) writes: >> >I'd like to write a simple vm_check program that returns >> >nothing except the amount of swap remaining... (which is >> >all I'm interested in... >> >> As you might have guessed from the output of /etc/pstat -s, >> there isn't simple value stored in the kernel that says "this >> much swap space is in use"; rather, pstat grovels through >> kernel data structures counting things up, and computes >> a total through a fairly hairy computation. I counted over >> 160 lines in pstat just to do what you're asking for. > Actually it depends on what version of ULTRIX you're > running. In V3.1 and earlier. It's the really hairy > stuff that Jeff mentioned. In V4.0 there is a data > structure called "swapu" that has how much is being > used for various things. The amount free is just the > total - the amount used. You can get total from adding > amount indicated in the "swdevt" table. [... source for simplified pstat -s omitted ...] Thanks for this piece of code. (on Ultrix4.0) it returns the amount of used and wasted swap space using less than 0.1 sec cpu time (in good ol' 512 byte blocks). Please compare: "/bin/time /etc/pstat -s": Machine Ultrix V swap space cpu sec VAX 11/785 3.1 66 M 2.4 - well, a 785... DECstation 5000 4.0 65 2.3 - hmm... DECsystem 5400 4.0 122 3.8 - qualifies as "fairly hairy" DECsystem 5820 4.0 127 3.8 - ditto DECsystem 5840 4.0 156 6.1 - !!! outrageous !!! it seems the faster the machine, the slower is pstat -s :-( +----------- Andi Karrer, Communication Systems, ETH Zuerich, Switzerland karrer@ks.id.ethz.ch karrer@czheth5a.bitnet