On Thu, Apr 28, 2011 at 23:41, David Rientjes <rientjes@xxxxxxxxxx> wrote:
On Thu, 28 Apr 2011, James Bottomley wrote:
Since 4a5fa3590f09 ([PARISC] slub: fix panic with DISCONTIGMEM) from
2.6.39-rc4, you can't actually select slub on m68k without CONFIG_ADVANCED
and CONFIG_SINGLE_MEMORY_CHUNK because it otherwises defaults to
discontigmem.
James tested hppa64 with my N_NORMAL_MEMORY fix and found that it turned
an SMP box into UP. ÂIf you've tested slub on m68k without regressions,
then perhaps you'd like to add a "|| M68K" to CONFIG_SLUB?
To be honest, I really don't see that fixing it. ÂAs soon as you
allocate memory beyond range zero, you move onto a non-zero node as far
as slub is concerned, and that will oops.
Possible nodes are represented in slub with N_NORMAL_MEMORY, so the
kmem_cache_node structures are allocated and initialized based on this
nodemask. ÂAs long as the memory ranges map to nodes set in the nodemask,
this should be fine.
I think what the N_NORMAL_MEMORY patch did is just make it take a whiile
before you start allocating from that range. ÂTry executing a memory
balloon on the platform; that was how we first demonstrated the problem
on parisc.
With parisc, you encountered an oops in add_partial() because the
kmem_cache_node structure for the memory range returned by page_to_nid()
was not allocated. Âinit_kmem_cache_nodes() takes care of this for all
memory ranges set in N_NORMAL_MEMORY.
Adding Christoph and Pekka to the cc if there is additional concerns about
slub on this architecture.
My ARAnyM instance has
System Memory: 276480K
14 MB at 0x00000000 (ST-RAM)
256 MB at 0x01000000 (alternate RAM)
and 137800KIB of swap, and survived the following program just fine:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[])
{
size_t size = 1048576;
size_t total = 0;
void *p;
while (size) {
p = malloc(size);
if (!p) {
printf("Failed to allocate %zu bytes\n", size);
size /= 2;
}
memset(p, 0xaa, size);
total += size;
printf("Using %zu / 0x%zx bytes of memory\n", total, total);
}
printf("Finished!\n");
return 0;
}
i.e. the OOM-killer just killed the program after it consumed all
available virtual
memory:
Out of memory: Kill process 1727 (malloctest) score 854 or sacrifice child
Killed process 1727 (malloctest) total-vm:361160kB, anon-rss:224164kB,
file-rss:0kB
malloctest: page allocation failure. order:0, mode:0x84d0
So SLUB really seems to work now.
Gr{oetje,eeting}s,
            Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
             Â Â -- Linus Torvalds
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