On Sun Jan 19, 2025 at 6:55 PM EST, Barry Song wrote: <snip> >> >>> >> >>> >> >>> However, with this workaround, we can't use transparent huge pages. >> >>> >> >>> Is the CMA_MIN_ALIGNMENT_BYTES requirement alignment only to support huge pages? >> No. CMA_MIN_ALIGNMENT_BYTES is limited by CMA_MIN_ALIGNMENT_PAGES, which >> is equal to pageblock size. Enabling THP just bumps the pageblock size. > > Currently, THP might be mTHP, which can have a significantly smaller > size than 32MB. For > example, on arm64 systems with a 16KiB page size, a 2MB CONT-PTE mTHP > is possible. > Additionally, mTHP relies on the CONFIG_TRANSPARENT_HUGEPAGE configuration. > > I wonder if it's possible to enable CONFIG_TRANSPARENT_HUGEPAGE > without necessarily > using 32MiB THP. If we use other sizes, such as 64KiB, perhaps a large > pageblock size wouldn't > be necessary? I think this should work by reducing MAX_PAGE_ORDER like Juan did for the experiment. But MAX_PAGE_ORDER is a macro right now, Kconfig needs to be changed and kernel needs to be recompiled. Not sure if it is OK for Juan's use case. -- Best Regards, Yan, Zi
