[uml-devel] kmalloc does not recover mem in 2.4.24

["Peter T. Breuer" <ptb@inv.it.uc3m.es>]

Howdy. I've been running 2.4.24-1um very happily for a good long time.
Since April, I believe. But I've just noticed that kmalloc does not seem
to recover memory. Here I've cooked up some demonstration code:

sh-2.03# free
             total       used       free     shared    buffers cached
Mem:         29524       4540      24984          0        140 2824
                         ^^^^^
-/+ buffers/cache:       1576      27948
Swap:            0          0          0

sh-2.03# insmod mem.o
tiny driver loaded


(this module uses kmalloc to allocate 1000 pages in its init function, 
and will release it in its exit function)

sh-2.03# free
             total       used       free     shared    buffers cached
Mem:         29524       8684      20840          0        140 2824
                         ^^^^^
-/+ buffers/cache:       5720      23804
Swap:            0          0          0

sh-2.03# rmmod mem
tiny driver unloaded

sh-2.03# free
             total       used       free     shared    buffers cached
Mem:         29524       8680      20844          0        140 2824
                         ^^^^^
-/+ buffers/cache:       5716      23808
Swap:            0          0          0


Same mem usage!  Nothing released.  I am running UML under kernel 2.6.3,
where it also shows timing anomalies - any sleep takes ages to complete.

Here's my test code:


#include <linux/major.h>
#include <linux/module.h>
#include <linux/version.h>
#include <linux/init.h>
#include <linux/slab.h>

#include <linux/blkdev.h>
#include <linux/blk.h>

int linux_version_code = LINUX_VERSION_CODE;

#define MAX_TINY 1024

static char ** tiny_cache;
static int max_tiny = MAX_TINY;

static int __init
tiny_init (void)
{
        int i, err;

        tiny_cache = kmalloc(sizeof(char *) * max_tiny, GFP_KERNEL);
        for (i = 0; i < max_tiny; i++) {

                tiny_cache[i] = kmalloc(PAGE_SIZE, GFP_KERNEL);
                if (!tiny_cache[i])
                        goto error_out;
        }
        printk (KERN_INFO "tiny driver loaded\n");
        return 0;

error_out:

        printk (KERN_ERR "tiny driver failed to load\n");
        while (--i >= 0) {
                kfree(tiny_cache[i]);
        }
        kfree(tiny_cache);
        return -EINVAL;
}

static void __exit
tiny_cleanup (void)
{

        int i;

        for (i = 0; i < max_tiny; i++) {
                kfree (tiny_cache[i]);
        }
        kfree(tiny_cache);
        printk (KERN_INFO "tiny driver unloaded\n");
}

module_init (tiny_init);
module_exit (tiny_cleanup);



Peter


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