I have a version of free I wrote for BusyBox that uses sysinfo (rather then
/proc) to get its information. Under 2.2.x it reports normal stuff, i.e.
[andersen@dillweed busybox]$ ./free
total used free shared buffers
Mem: 127800 124268 3532 16956 7544
Swap: 128516 13584 114932
Total: 256316 137852 118464
while under 2.2.0-test1-ac7 it reports wierd numbers (~ #/4096)
[andersen@dillweed busybox]$ ./free
total used free shared buffers
Mem: 30 11 19 0 1
Swap: 31 0 31
Total: 61 11 50
After investigating the problem, it turns out that somewhere during 2.3.x the
values for memory stored in struct sysinfo changed from being stored as bytes
to being units of PAGE_SIZE, but kernel/info.c was never updated to reflect
this change in definition.
Breaking free isn't that big of a deal, but I also use sysinfo in init to check
that the box has enough ram from within the init process (and no, mounting
/proc from within init and reading /proc/meminfo is not a good solution.
BusyBox is often used in embedded systems where /proc is not compiled in).
The following patch reinstates the traditional sysinfo(2) interface by
returning bytes (not units of PAGE_SIZE) for memory values.
An additional patch suggestion (not included here) would be to eliminate the
supurfluous "mem_unit" variable from struct_sysinfo in include/linux/kernel.h
and arch/*/mm/init.c.
-Erik
--
Erik B. Andersen Web: http://www.xmission.com/~andersen/
email: andersee@debian.org
--This message was written using 73% post-consumer electrons--
--- linux/kernel/info.c.orig Mon Aug 23 12:15:53 1999
+++ linux/kernel/info.c Sun Jun 4 01:13:11 2000
@@ -2,6 +2,8 @@
* linux/kernel/info.c
*
* Copyright (C) 1992 Darren Senn
+ * Fixed to once again return bytes instead of page counts,
+ * June 2000, by Erik Andersen <andersee@debian.org>
*/
/* This implements the sysinfo() system call */
@@ -10,7 +12,6 @@
#include <linux/unistd.h>
#include <linux/swap.h>
#include <linux/smp_lock.h>
-
#include <asm/uaccess.h>
asmlinkage long sys_sysinfo(struct sysinfo *info)
@@ -31,6 +32,17 @@
si_meminfo(&val);
si_swapinfo(&val);
+
+ /* These are in units of PAGE_SIZE, but this interface
+ * has always returned bytes. Make it return bytes */
+ val.totalram*=PAGE_SIZE;
+ val.freeram*=PAGE_SIZE;
+ val.sharedram*=PAGE_SIZE;
+ val.bufferram*=PAGE_SIZE;
+ val.totalswap*=PAGE_SIZE;
+ val.freeswap*=PAGE_SIZE;
+ val.totalhigh*=PAGE_SIZE;
+ val.freehigh*=PAGE_SIZE;
if (copy_to_user(info, &val, sizeof(struct sysinfo)))
return -EFAULT;
-
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