Hi Barry,
On 27/10/24 16:52, Barry Song wrote:
On Mon, Oct 28, 2024 at 1:58 AM Maíra Canal <mcanal@xxxxxxxxxx> wrote:
If we add ``thp_anon=32,64KB:always`` to the kernel command line, we
will see the following error:
[ 0.000000] huge_memory: thp_anon=32,64K:always: error parsing string, ignoring setting
This happens because the correct format isn't ``thp_anon=<size>,<size>[KMG]:<state>```,
as [KMG] must follow each number to especify its unit. So, the correct
format is ``thp_anon=<size>[KMG],<size>[KMG]:<state>```.
what if 32768,64K: always?
``32768,64K:always`` works. From the kernel parameters documentation, I
see that:
"Finally, the [KMG] suffix is commonly described after a number of
kernel parameter values. These ‘K’, ‘M’, and ‘G’ letters represent the
_binary_ multipliers ‘Kilo’, ‘Mega’, and ‘Giga’, equaling 2^10, 2^20,
and 2^30 bytes respectively. Such letter suffixes can also be entirely
omitted"
AFAIU this means that [KMG] can be omitted if we use bytes. But if we
don't use bytes, it cannot be omitted.
Best Regards,
- Maíra
Therefore, adjust the documentation to reflect the correct format of the
parameter ``thp_anon=``.
Fixes: dd4d30d1cdbe ("mm: override mTHP "enabled" defaults at kernel cmdline")
Signed-off-by: Maíra Canal <mcanal@xxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 2 +-
Documentation/admin-guide/mm/transhuge.rst | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1518343bbe22..1666576acc0e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6688,7 +6688,7 @@
0: no polling (default)
thp_anon= [KNL]
- Format: <size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>
+ Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
state is one of "always", "madvise", "never" or "inherit".
Control the default behavior of the system with respect
to anonymous transparent hugepages.
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 203ba7aaf5fc..745055c3dc09 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -303,7 +303,7 @@ control by passing the parameter ``transparent_hugepage=always`` or
kernel command line.
Alternatively, each supported anonymous THP size can be controlled by
-passing ``thp_anon=<size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>``,
+passing ``thp_anon=<size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>``,
where ``<size>`` is the THP size (must be a power of 2 of PAGE_SIZE and
supported anonymous THP) and ``<state>`` is one of ``always``, ``madvise``,
``never`` or ``inherit``.
--
2.46.2
