From: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
The commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP
boundaries") incured regression for stress-ng pthread benchmark [1].
It is because THP get allocated to pthread's stack area much more possible
than before. Pthread's stack area is allocated by mmap without VM_GROWSDOWN
or VM_GROWSUP flag, so kernel can't tell whether it is a stack area or not.
The MAP_STACK flag is used to mark the stack area, but it is a no-op on
Linux. Mapping MAP_STACK to VM_NOHUGEPAGE to prevent from allocating
THP for such stack area.
With this change the stack area looks like:
fffd18e10000-fffd19610000 rw-p 00000000 00:00 0
Size: 8192 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 12 kB
Pss: 12 kB
Pss_Dirty: 12 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 12 kB
Referenced: 12 kB
Anonymous: 12 kB
KSM: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB
THPeligible: 0
VmFlags: rd wr mr mw me ac nh
The "nh" flag is set.
[1] https://lore.kernel.org/linux-mm/202312192310.56367035-oliver.sang@xxxxxxxxx/
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Tested-by: Oliver Sang <oliver.sang@xxxxxxxxx>
Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: Huang, Ying <ying.huang@xxxxxxxxx>
Signed-off-by: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
---
include/linux/mman.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 40d94411d492..dc7048824be8 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -156,6 +156,7 @@ calc_vm_flag_bits(unsigned long flags)
return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
_calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) |
_calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) |
+ _calc_vm_trans(flags, MAP_STACK, VM_NOHUGEPAGE) |
arch_calc_vm_flag_bits(flags);
}
--
2.41.0
