On 21.07.25 17:55, Lorenzo Stoakes wrote:
Rather confusingly, setting all Transparent Huge Page sysfs settings to
"never" does not in fact result in THP being globally disabled.
Rather, it results in khugepaged being disabled, but one can still obtain
THP pages using madvise(..., MADV_COLLAPSE).
This is something that has remained poorly documented for some time, and it
is likely the received wisdom of most users of THP that never does, in
fact, mean never.
It is therefore important to highlight, very clearly, that this is not the
ase.
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
Can we also somehow tone down or clarify the "entirely disabled"?
Something as simple as
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index bd49b46398c92..2267d22277238 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -107,7 +107,7 @@ sysfs
Global THP controls
-------------------
-Transparent Hugepage Support for anonymous memory can be entirely disabled
+Transparent Hugepage Support for anonymous memory can be mostly disabled
(mostly for debugging purposes) or only enabled inside MADV_HUGEPAGE
regions (to avoid the risk of consuming more memory resources) or enabled
system wide. This can be achieved per-supported-THP-size with one of::
--
Cheers,
David / dhildenb
