I reproduced this problem in 2.4.18 and visually verified it in
2.4.21-pre5. I haven't look at any other kernels.
Buffer Heads tend to be allocated in low memory (SLAB_NOFS) but point to
pages in high memory. If low memory is under heavy pressure, but high
memory is not, then buffer heads in low memory that point to buffers in
high memory are never freed. This can cause OOM errors when there is
still plenty of memory and plenty of buffer heads that could be easily
freed.
Addint the following while loop to
try_to_free_pages/try_to_free_pages_zone and trying to free pages again
seems to alleviate the problem.
Ross
/* Problem, we couldn't free up the memory we want.
Currently buffer heads all end up in lowmem, so
we may be able to free up some low mem by freeing
up some highmem. Try to do that. */
while (pgdat) {
for (zone = pgdat->node_zones + MAX_NR_ZONES-1;
zone > classzone &&
zone >= pgdat->node_zones ;
zone--) {
shrink_caches(zone, priority, gfp_mask,
nr_pages *
(PAGE_SIZE /
sizeof(struct
buffer_head) + 1)
* 8);
}
pgdat = pgdat->node_next;
}
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This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:38 EST