Hi
The patch c33d6c06f60f710f0305ae792773e1c2560e1e51 ("mm, page_alloc: avoid
looking up the first zone in a zonelist twice") breaks memory management
on PA-RISC.
The PA-RISC system is not NUMA, but the chipset maps physical memory to
three distinct ranges, so the kernel sets up three nodes. My machine has
7GiB RAM and the memory is mapped to these ranges:
Memory Ranges:
0) Start 0x0000000000000000 End 0x000000003fffffff Size 1024 MB
1) Start 0x0000000100000000 End 0x00000001bfdfffff Size 3070 MB
2) Start 0x0000004040000000 End 0x00000040ffffffff Size 3072 MB
Total Memory: 7166 MB
On node 0 totalpages: 262144
free_area_init_node: node 0, pgdat 405e44d0, node_mem_map 415ed000
Normal zone: 3584 pages used for memmap
Normal zone: 0 pages reserved
Normal zone: 262144 pages, LIFO batch:31
On node 1 totalpages: 785920
free_area_init_node: node 1, pgdat 405e5140, node_mem_map 140000000
Normal zone: 10745 pages used for memmap
Normal zone: 0 pages reserved
Normal zone: 785920 pages, LIFO batch:31
On node 2 totalpages: 786432
free_area_init_node: node 2, pgdat 405e5db0, node_mem_map 4080000000
Normal zone: 10752 pages used for memmap
Normal zone: 0 pages reserved
Normal zone: 786432 pages, LIFO batch:31
Prior to the patch c33d6c06f60f710f0305ae792773e1c2560e1e51, the kernel
could use all 7GiB of RAM as file cache. After this patch, the kernel
fills the first 1GiB zone with cache and then starts reclaiming the cache
(or sometimes even swapping) instead of using the remaining two zones as a
file cache.
The bug can be reproduced by reading 2GiB file and noticing that the
amount of cached memory stays near 1GiB.
Mikulas
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