> > So shouldn't [the name of] the value the kernel provides for recommended > > alignment be equally implementation agnostic? > > Is sys/kernel/mm/transparent_hugepage directory implementation > agnostic in the first place?
It's about as agnostic as MADV_HUGEPAGE :-) > If we want to fully take advantage of the feature (i.e. NPT and qemu > first 2M of guest physical ram where usually kernel resides) userspace > has to know the alignment size the kernel recommends. This is KVM specific, so my gut reaction is you should be asking KVM. > Only thing I'm undecided about is if this should be called > hpage_pmd_size or just hpage_size. Suppose amd/intel next year adds > 64k pages too and the kernel decides to use them too if it fails to > allocate a 2M page. So we escalate the fallback from 2M -> 64k -> 4k, > and HPAGE_PMD_SIZE becomes 64k. Still qemu has to align on the max > possible hpage_size provided by transparent hugepage. So with this new > reasoning I think hpage_size or max_hpage_size would be better sysfs > name for this. What do you think? Agreed. > hpage_size or max_hpage_size? No particular preference. Or you could have .../page_sizes list all available sizes, and have qemu take the first one (or last depending on sort order). Paul
