On 2024/5/7 18:20, Ryan Roberts wrote:
On 06/05/2024 09:46, Baolin Wang wrote:
Anonymous pages have already been supported for multi-size (mTHP) allocation
through commit 19eaf44954df, that can allow THP to be configured through the
sysfs interface located at '/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled'.
However, the anonymous shared pages will ignore the anonymous mTHP rule
configured through the sysfs interface, and can only use the PMD-mapped
THP, that is not reasonable. Many implement anonymous page sharing through
mmap(MAP_SHARED | MAP_ANONYMOUS), especially in database usage scenarios,
therefore, users expect to apply an unified mTHP strategy for anonymous pages,
also including the anonymous shared pages, in order to enjoy the benefits of
mTHP. For example, lower latency than PMD-mapped THP, smaller memory bloat
than PMD-mapped THP, contiguous PTEs on ARM architecture to reduce TLB miss etc.
The primary strategy is similar to supporting anonymous mTHP. Introduce
a new interface '/mm/transparent_hugepage/hugepage-XXkb/shmem_enabled',
which can have all the same values as the top-level
Didn't we agree that "force" would not be supported for now, and would return an
error when attempting to set for a non-PMD-size hugepage-XXkb/shmem_enabled (or
indirectly through inheritance)?
Yes. Sorry, I did not explain it in detail in the cover letter. Please
see patch 5 you already commented.
