chris@lxn.UUCP (Christopher D. Orr) (03/31/88)
I have been trying to find a nice, clean way to determine system
memory under SYS V 2.2. I have come up with two solutions to this
problem. However, there must be a cleaner/faster way :-).
Solution 1: The command 'wc -c /dev/mem' seems to work though it
takes *FOREVER* on systems with large amounts on memory.
Solution 2: The following 'C' program reports system memory much
faster that Solution 1, but is still fairly slow:
#include <stdio.h>
#include <fcntl.h>
extern int errno;
static char BUF[32768];
void main()
{
long int L;
int M;
M = open("/dev/mem",O_RDONLY);
if (M < 0)
{
printf("Error: unable to open /dev/mem. errno=%d\n",errno);
exit(1);
}
for (L=0;read(M,BUF,16384) == 16384 ;++L);
printf("Memory Size: %ld\n",L * 16384);
}
Any other solutions are welcome (especially those that are faster :-)
---
Christopher D. Orr | US MAIL: Alcyone Inc.
UUCP: vu-vlsi\ | Lanark Building
ihnp4 - !lehi3b15!lxn!chris | Center Valley, PA 18034
c11ux / | Voice: (215) 282-4525edw@IUS1.CS.CMU.EDU (Eddie Wyatt) (03/31/88)
> I have been trying to find a nice, clean way to determine system > memory under SYS V 2.2. I have come up with two solutions to this > problem. However, there must be a cleaner/faster way :-). > .... > Any other solutions are welcome (especially those that are faster :-) If what you are really interested in is the memory currently available to a given process I suggest using sbrk. sbrk memory in fix block sizes until sbrk fails. -- Eddie Wyatt e-mail: edw@ius1.cs.cmu.edu
ram%shukra@Sun.COM (Renu Raman, Taco Bell Microsystems) (04/01/88)
In article <248@lxn.UUCP> chris@lxn.UUCP (Christopher D. Orr) writes: > >I have been trying to find a nice, clean way to determine system >memory under SYS V 2.2. I have come up with two solutions to this >problem. However, there must be a cleaner/faster way :-). > >Solution 1: The command 'wc -c /dev/mem' seems to work though it > takes *FOREVER* on systems with large amounts on memory. > >Solution 2: The following 'C' program reports system memory much > faster that Solution 1, but is still fairly slow: > #include <stdio.h> > #include <fcntl.h> > > extern int errno; > static char BUF[32768]; > > void main() > { > long int L; > int M; > > M = open("/dev/mem",O_RDONLY); > if (M < 0) > { > printf("Error: unable to open /dev/mem. errno=%d\n",errno); > exit(1); > } > > for (L=0;read(M,BUF,16384) == 16384 ;++L); > printf("Memory Size: %ld\n",L * 16384); > } > >Any other solutions are welcome (especially those that are faster :-) > >--- >Christopher D. Orr | US MAIL: Alcyone Inc. >UUCP: vu-vlsi\ | Lanark Building > ihnp4 - !lehi3b15!lxn!chris | Center Valley, PA 18034 > c11ux / | Voice: (215) 282-4525 Bezerkely and its derivatives have a kernel variable called _physmem. Just get its location and read that variable from /dev/kmem. _physmem is the total memory in expressed in clicks (system pages). There must be an equivalent in Sys V. too. You may need nlist or its variant for Sys. V. Renu Raman
davy@ea.ecn.purdue.edu (Dave Curry) (04/01/88)
In article <248@lxn.UUCP> chris@lxn.UUCP (Christopher D. Orr) writes: > >I have been trying to find a nice, clean way to determine system >memory under SYS V 2.2. I have come up with two solutions to this >problem. However, there must be a cleaner/faster way :-). > Of course the simplest and fastest way, assuming you have the permissions, is to just go dig it out of the kernel. --Dave /* * Figure out how much memory there is on a machine. This works under * Berkeley UNIX. It should work under System V if you change the * UNIX define to "/unix" instead of "/vmunix". * * Of course, if you don't have read permission on the kernel and * kernel memory, this won't work. * * Dave Curry * Purdue University * Engineering Computer Network * davy@intrepid.ecn.purdue.edu */ #include <sys/param.h> #include <sys/types.h> #include <nlist.h> #include <stdio.h> #ifndef ctob /* For System V */ #include <sys/sysmacros.h> #endif #define UNIX "/vmunix" #define KMEM "/dev/kmem" struct nlist nl[] = { #define X_PHYSMEM 0 { "_physmem" }, #define X_MAXMEM 1 { "_maxmem" }, { NULL } }; main() { int kmem; int maxmem, physmem; /* * Look up addresses of variables. */ if ((nlist(UNIX, nl) < 0) || (nl[0].n_type == 0)) { fprintf(stderr, "%s: no namelist.\n", UNIX); exit(1); } /* * Open kernel memory. */ if ((kmem = open(KMEM, 0)) < 0) { perror(KMEM); exit(1); } /* * Read variables. */ lseek(kmem, (long) nl[X_PHYSMEM].n_value, 0); read(kmem, (char *) &physmem, sizeof(int)); lseek(kmem, (long) nl[X_MAXMEM].n_value, 0); read(kmem, (char *) &maxmem, sizeof(int)); close(kmem); /* * Print the numbers. The internal representation is * in units of core clicks; convert to bytes. */ printf("Physical machine memory: %d\n", ctob(physmem)); printf("Max memory available to a process: %d\n", ctob(maxmem)); exit(0); }
dean@homxb.UUCP (D.JONES) (04/02/88)
In article <1271@PT.CS.CMU.EDU>, edw@IUS1.CS.CMU.EDU (Eddie Wyatt) writes: > > I have been trying to find a nice, clean way to determine system > > memory under SYS V 2.2. I have come up with two solutions to this > > problem. However, there must be a cleaner/faster way :-). > > Any other solutions are welcome (especially those that are faster :-) > If what you are really interested in is the memory currently available > to a given process I suggest using sbrk. sbrk memory > in fix block sizes until sbrk fails. > Eddie Wyatt e-mail: edw@ius1.cs.cmu.edu Now you know how much memory you have for the current process, but do you have to sbrk() it back if you are going to use malloc() ??? A call to ulimit() on SysV 2.2 with an arg of 3 will return the max brk value for the current process. What about something <simple> like: long memavail() { return(ulimit(3) - (long)sbrk(0)) } It looks like this will work on our SunOS 4.0 machines also. I'm Just starting to get into this UNIX stuff, don't flame me if this is a bozo idea... Dean S Jones AT&T Gateways!homxb!dean
dwc@homxc.UUCP (Malaclypse the Elder) (04/02/88)
In article <248@lxn.UUCP>, chris@lxn.UUCP (Christopher D. Orr) writes: > > I have been trying to find a nice, clean way to determine system > memory under SYS V 2.2. I have come up with two solutions to this > problem. However, there must be a cleaner/faster way :-). > i believe there is a system variable called physmem (or something like that). so all you have to do is to find the address of the variable, open /dev/mem (or kmem, i'm never sure which) and read that value (ala ps, sysdef, etc.) danny chen ihnp4!homxc!dwc
edw@IUS1.CS.CMU.EDU (Eddie Wyatt) (04/04/88)
memory size via sbrk deleted. > Now you know how much memory you have for the current process, but > do you have to sbrk() it back if you are going to use malloc() ??? Consider this as an independent facility at the shell level. It's useful for things like finding out if the current machine that you are running on has enough memory to load your lisp job and maintain it. -- Eddie Wyatt e-mail: edw@ius1.cs.cmu.edu
dannyb@kulcs.uucp (Danny Backx) (04/04/88)
In article <248@lxn.UUCP> chris@lxn.UUCP (Christopher D. Orr) writes: >I have been trying to find a nice, clean way to determine system >memory under SYS V 2.2. I have come up with two solutions to this >problem. However, there must be a cleaner/faster way :-). How about opening /dev/mem and seeking to the end ? The manual entry for lseek(2) says the return value is the position you got at. So, if you seek to the end (offset 0 relative to the EOF), the return value of lseek should be the amount of memory your system has. I don't know if this works on /dev/mem. It works on ordinary files. If your program works, this should, too. The system call you should issue is : long lseek(), pos ; pos = lseek(M, 0L, 2); Don't forget the declaration of lseek() !!! Danny -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Danny Backx | mail: Katholieke Universiteit Leuven Tel: +32 16 200656 x 3537 | Dept. Computer Science E-mail: dannyb@kulcs.UUCP | Celestijnenlaan 200 A ... mcvax!prlb2!kulcs!dannyb | B-3030 Leuven dannyb@blekul60.BITNET | Belgium
mouse@mcgill-vision.UUCP (der Mouse) (04/13/88)
In article <248@lxn.UUCP>, chris@lxn.UUCP (Christopher D. Orr) writes: > I have been trying to find a nice, clean way to determine system > memory under SYS V 2.2. > Solution 2: [This is faster than Solution 1, but still slow]: [program] Well, you could speed it up by doing a more intelligent search technique than linear search: /****** UNTESTED (no SV system to test it on) ******/ #include <stdio.h> #include <fcntl.h> extern int errno; static char buf; main() { long int l; long int m; long int h; int fd; fd = open("/dev/mem",O_RDONLY); /* check for fd<0 omitted for brevity */ l = 1; h = 2; while (1) { lseek(fd,h,L_SET); /* or whatever the SV way is */ if (read(fd,&buf,1) != 1) break; l = h; h *= 2; } while (h-l > 1) { m = (h + l) / 2; lseek(fd,m,L_SET); /* or whatever */ if (read(fd,&buf,1) == 1) l = m; else h = m; } printf("%ld bytes accessible via /dev/mem\n",h); exit(0); } der Mouse uucp: mouse@mcgill-vision.uucp arpa: mouse@larry.mcrcim.mcgill.edu