On Fri, Aug 9, 2024 at 5:19 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > 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 ;) I prefer the current approach because it effectively filters cases like this. [ 0.000000] huge_memory: thp_anon=8K:inherit: cannot parse, ignored [ 0.000000] Unknown kernel command line parameters "thp_anon=8K:inherit", will be passed to user space. if we put multiple sizes together, 8K,32K,64K:always We can't determine whether this command line is legal or illegal as it is partially legal and partially illegal. Just my two cents :-) > > -- > Cheers, > > David / dhildenb Thanks Barry
