Re: crash in kmem_cache_init

Mel Gorman
2008-01-18T21:30:26Z

On (18/01/08 10:47), Christoph Lameter didst pronounce:
> On Thu, 17 Jan 2008, Olaf Hering wrote:
>
> > early_node_map[1] active PFN ranges
> > 1: 0 -> 892928
> > Could not find start_pfn for node 0
>
> Corrupted min_pfn?
>

Doubtful. Node 0 has no memory but it is still being initialised.

Still, I looked closer at what is going on when that message gets
displayed and I see this in free_area_init_nodes()

for_each_online_node(nid) {
pg_data_t *pgdat = NODE_DATA(nid);
free_area_init_node(nid, pgdat, NULL,
find_min_pfn_for_node(nid), NULL);

/* Any memory on that node */
if (pgdat->node_present_pages)
node_set_state(nid, N_HIGH_MEMORY);
check_for_regular_memory(pgdat);
}

This "Any memory on that node" thing is new and it says if there is any
memory on the node, set N_HIGH_MEMORY. Fine I guess, I haven't tracked these
changes closely. It calls check_for_regular_memory() which looks like

static void check_for_regular_memory(pg_data_t *pgdat)
{
#ifdef CONFIG_HIGHMEM
enum zone_type zone_type;

for (zone_type = 0; zone_type <= ZONE_NORMAL; zone_type++) {
struct zone *zone = &pgdat->node_zones[zone_type];
if (zone->present_pages)
node_set_state(zone_to_nid(zone), N_NORMAL_MEMORY);
}
#endif
}

i.e. go through the other zones and if any of them have memory, set
N_NORMAL_MEMORY. But... it only does this on CONFIG_HIGHMEM which on
PPC64 is not going to be set so N_NORMAL_MEMORY never gets set on
POWER.... That sounds bad.

mel@arnold:~/git/linux-2.6/mm$ grep -n N_NORMAL_MEMORY slab.c
1593: for_each_node_state(nid, N_NORMAL_MEMORY) {
1971: for_each_node_state(node, N_NORMAL_MEMORY) {
2102: for_each_node_state(node, N_NORMAL_MEMORY) {
3818: for_each_node_state(node, N_NORMAL_MEMORY) {

and one of them is in kmem_cache_init(). That seems very significant.
Christoph, can you think of possibilities of where N_NORMAL_MEMORY not
being set would cause trouble for slab?

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab