On Wed, Sep 17, 2025 at 12:05 PM David Hildenbrand <da...@redhat.com> wrote: > > On 17.09.25 20:51, Kyle Meyer wrote: > > On Wed, Sep 17, 2025 at 09:02:55AM +0200, David Hildenbrand wrote: > >> > >>>> + > >>>> + 0 - Enable soft offline > >>>> + 1 - Disable soft offline for HugeTLB pages > >>>> + > >>>> +Supported values:: > >>>> + > >>>> + 0 - Soft offline is disabled > >>>> + 1 - Soft offline is enabled > >>>> + 3 - Soft offline is enabled (disabled for HugeTLB pages) > >>> > >>> This looks very adhoc even though existing behavior is preserved. > >>> > >>> - Are HugeTLB pages the only page types to be considered ? > >>> - How the remaining bits here are going to be used later ? > >>> > >> > >> What I proposed (that could be better documented here) is that all other > >> bits except the first one will be a disable mask when bit 0 is set. > >> > >> 2 - ... but yet disabled for hugetlb > >> 4 - ... but yet disabled for $WHATEVER > >> 8 - ... but yet disabled for $WHATEVERELSE > >> > >>> Also without a bit-wise usage roadmap, is not changing a procfs > >>> interface (ABI) bit problematic ? > >> > >> For now we failed setting it to values that are neither 0 or 1, IIUC > >> set_enable_soft_offline() correctly? > > > > Yes, -EINVAL will be returned. > > > >> So there should not be any problem, or which scenario do you have in mind? > > > > Here's an alternative approach. > > > > Do not modify the existing sysctl parameter: > > > > /proc/sys/vm/enable_soft_offline > > > > 0 - Soft offline is disabled > > 1 - Soft offline is enabled > > > > Instead, introduce a new sysctl parameter: > > > > /proc/sys/vm/enable_soft_offline_hugetlb > > > > 0 - Soft offline is disabled for HugeTLB pages > > 1 - Soft offline is enabled for HugeTLB pages > > > > and note in documentation that this setting only takes effect if > > enable_soft_offline is enabled. > > > > Anshuman (and David), would you prefer this? > > Hmm, at least I don't particularly like that. For each new exception we
+1. Given /proc/sys/vm/enable_soft_offline is extensible, I would prefer a compact userspace API. > would create a new file, and the file has weird semantics such that it > has no meaning when enable_soft_offline=0. > > -- > Cheers > > David / dhildenb >
