Super pages

[Dr. Baud]

> On 23/02/2011 14:03, Dr. Baud wrote:
> >
> >      In general, is it unadvisable to disable super pages?
> 
> I don't think there would be any effect on the stability of operation if 
> you disable superpages, but generally (except in cases of CPU bugs) you 
> would not need to. Your system should operate a bit faster with 
> superpages enabled.

    When is the memory allocated via contigmalloc freed? I have a test kernel 
module that allocates memory in 8MB chucks until contigmalloc says enough (the 
ginormous.c/Makefile attachment). I also have a bash script that displays the
interesting memory related kernel state variables (the mem attachement).
    When I load and unload the kernel module and display the VM pages stats I
never see the wired pages nor free pages change:

 vm.pmap.pg_ps_enabled: 1

SYSTEM MEMORY INFORMATION:
mem_phys:    =   2138693632 (   2039MB)        Physical memory tunable
mem_user:    =   2107297792 (   2009MB)        User space memory available
mem_real:    =   2146893824 (   2047MB)        Maximum physical pages
mem_all:     =   2075402240 (   1979MB) [100%] Virual memory pages
mem_cache:   =            0 (      0MB) [  0%] Cached: almost avail. to allocat
mem_inactive:=      7360512 (      7MB) [  0%] Inactive: recently unreferenced
mem_active:  +      8765440 (      8MB) [  0%] Active: recently referenced
mem_wire:          31395840 (     29MB) [  1%] Wired: disabled for paging out
mem_free:    +   2027589632 (   1933MB) [ 97%] Free: fully available
-------------- ------------ -----------
mem_hw:      =   2147483648 (   2048MB)        Virual memory (cached, etc.)

kldload /sys/modules/ginormous/ginormous.ko
Ginormous module loading
Ginormous contigmalloc failed(229):

SYSTEM MEMORY INFORMATION:
mem_phys:    =   2138693632 (   2039MB)        Physical memory tunable
mem_user:    =    180330496 (    171MB)        User space memory available
mem_real:    =   2146893824 (   2047MB)        Maximum physical pages
mem_all:     =   2075402240 (   1979MB) [100%] Virual memory pages
mem_cache:   =     22237184 (     21MB) [  1%] Cached: almost avail. to allocat
mem_inactive:=       253952 (      0MB) [  0%] Inactive: recently unreferenced
mem_active:  +      2387968 (      2MB) [  0%] Active: recently referenced
mem_wire:        1958363136 (   1867MB) [ 94%] Wired: disabled for paging out
mem_free:    +     91795456 (     87MB) [  4%] Free: fully available
-------------- ------------ -----------
mem_hw:      =   2147483648 (   2048MB)        Virual memory (cached, etc.)


kldunload ginormous
Ginormous module unloading
Warning: memory type GINORMOUS leaked memory on destroy (229 allocations, 
1920991232 bytes leaked).

SYSTEM MEMORY INFORMATION:
mem_phys:    =   2138693632 (   2039MB)        Physical memory tunable
mem_user:    =    180314112 (    171MB)        User space memory available
mem_real:    =   2146893824 (   2047MB)        Maximum physical pages
mem_all:     =   2075402240 (   1979MB) [100%] Virual memory pages
mem_cache:   =     21565440 (     20MB) [  1%] Cached: almost avail. to allocat
mem_inactive:=       413696 (      0MB) [  0%] Inactive: recently unreferenced
mem_active:  +      2842624 (      2MB) [  0%] Active: recently referenced
mem_wire:        1958379520 (   1867MB) [ 94%] Wired: disabled for paging out
mem_free:    +     91807744 (     87MB) [  4%] Free: fully available
-------------- ------------ -----------
mem_hw:      =   2147483648 (   2048MB)        Virual memory (cached, etc.)

    Note that this behavior occurs whether superpages are enabled or not. Anyone 
have
and explanation?

    Dr.


      
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#include <sys/types.h>
#include <sys/module.h>
#include <sys/malloc.h>
#include <sys/systm.h>  /* uprintf */
#include <sys/param.h>  /* defines used in kernel.h */
#include <sys/kernel.h> /* types used in module initialization */
#include <sys/conf.h>   /* cdevsw struct */

MALLOC_DEFINE(M_GINORMOUS, "GINORMOUS", "Ginormous Kernel Module");

#define BUFSIZE (8*1024*1024)
#define NMALLOCS 241

static int
ginormous_loader(struct module *m, int what, void *arg)
{
    int err = 0;
    void *mem[NMALLOCS];

    switch (what)
    {
    case MOD_LOAD:                /* kldload */
        {
        int i;

        printf("Ginormous module loading\n");

        for (i = 0; i < NMALLOCS; i++) {
            if ((mem[i] = contigmalloc( BUFSIZE,
                                        M_GINORMOUS, 
                                        0, 
                                        0UL, 
                                        ~0UL, 
                                        PAGE_SIZE,
                                        0)) == NULL) {
                printf("Ginormous contigmalloc failed(%d):\n", i);
                break;
            }
        }
        }
        break;

    case MOD_UNLOAD:
        printf("Ginormous module unloading\n");
        break;

    default:
        err = EINVAL;
        break;
    }
    return(err);
}

DEV_MODULE(ginormous, ginormous_loader, NULL);
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