On 08.08.24 12:16, Ryan Roberts wrote:
Add thp_anon= cmdline parameter to allow specifying the default enablement of each supported anon THP size. The parameter accepts the following format and can be provided multiple times to configure each size: thp_anon=<size>[KMG]:<value> See Documentation/admin-guide/mm/transhuge.rst for more details. Configuring the defaults at boot time is useful to allow early user space to take advantage of mTHP before its been configured through sysfs.
I suspect a khugeapged enhancement and/or kernel-config-dependant defaults and/or early system settings will also be able to mitigate that without getting kernel cmdlines involved in the future.
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> --- Hi All, I've split this off from my RFC at [1] because Barry highlighted that he would benefit from it immediately [2]. There are no changes vs the version in that series. It applies against today's mm-unstable (275d686abcb59). (although I had to fix a minor build bug in stackdepot.c due to MIN() not being defined in this tree). Thanks, Ryan .../admin-guide/kernel-parameters.txt | 8 +++ Documentation/admin-guide/mm/transhuge.rst | 26 +++++++-- mm/huge_memory.c | 55 ++++++++++++++++++- 3 files changed, 82 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index bcdee8984e1f0..5c79b58c108ec 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6631,6 +6631,14 @@ <deci-seconds>: poll all this frequency 0: no polling (default) + thp_anon= [KNL] + Format: <size>[KMG]:always|madvise|never|inherit + Can be used to control the default behavior of the + system with respect to anonymous transparent hugepages. + Can be used multiple times for multiple anon THP sizes. + See Documentation/admin-guide/mm/transhuge.rst for more + details. + threadirqs [KNL,EARLY] Force threading of all interrupt handlers except those marked explicitly IRQF_NO_THREAD. diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 24eec1c03ad88..f63b0717366c6 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -284,13 +284,27 @@ that THP is shared. Exceeding the number would block the collapse:: A higher value may increase memory footprint for some workloads. -Boot parameter -============== +Boot parameters +=============== -You can change the sysfs boot time defaults of Transparent Hugepage -Support by passing the parameter ``transparent_hugepage=always`` or -``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` -to the kernel command line. +You can change the sysfs boot time default for the top-level "enabled" +control by passing the parameter ``transparent_hugepage=always`` or +``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` to the +kernel command line. + +Alternatively, each supported anonymous THP size can be controlled by +passing ``thp_anon=<size>[KMG]:<state>``, where ``<size>`` is the THP size +and ``<state>`` is one of ``always``, ``madvise``, ``never`` or +``inherit``. + +For example, the following will set 64K THP to ``always``:: + + thp_anon=64K:always + +``thp_anon=`` may be specified multiple times to configure all THP sizes as +required. If ``thp_anon=`` is specified at least once, any anon THP sizes +not explicitly configured on the command line are implicitly set to +``never``.
I suggest documenting that "thp_anon=" will not effect the value of "transparent_hugepage=", or any configured default.
Wondering if a syntax like thp_anon=16K,32K,64K:always;1048K,2048K:madvise (one could also support ranges, like "16K-64K") Would be even better. Then, maybe only allow a single instance. Maybe consider it if it's not too crazy to parse ;) -- Cheers, David / dhildenb
