On Mon, Feb 17, 2025 at 7:59 AM Usama Arif usamaarif642@gmail.com wrote:
On 11/02/2025 00:40, Nico Pache wrote:
setting /transparent_hugepages/enabled=always allows applications to benefit from THPs without having to madvise. However, the pf handler takes very few considerations to decide weather or not to actually use a THP. This can lead to a lot of wasted memory. khugepaged only operates on memory that was either allocated with enabled=always or MADV_HUGEPAGE.
Introduce the ability to set enabled=defer, which will prevent THPs from being allocated by the page fault handler unless madvise is set, leaving it up to khugepaged to decide which allocations will collapse to a THP. This should allow applications to benefits from THPs, while curbing some of the memory waste.
Signed-off-by: Nico Pache npache@redhat.com
include/linux/huge_mm.h | 15 +++++++++++++-- mm/huge_memory.c | 31 +++++++++++++++++++++++++++---- 2 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 93e509b6c00e..fb381ca720ea 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -44,6 +44,7 @@ enum transparent_hugepage_flag { TRANSPARENT_HUGEPAGE_UNSUPPORTED, TRANSPARENT_HUGEPAGE_FLAG, TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
TRANSPARENT_HUGEPAGE_DEFER_PF_INST_FLAG,No strong preference, but maybe just TRANSPARENT_HUGEPAGE_DEFER_FLAG might be better?
Not a bad idea, TRANSPARENT_HUGEPAGE_DEFER_PF_INST_FLAG is pretty long!