On Tue, Apr 21, 2026 at 08:58:59AM +0800, Huang, Ying wrote: > "Michael S. Tsirkin" <[email protected]> writes: > > > Add pghint_t, a bitwise type for communicating page allocation hints > > between the allocator and callers. Define PGHINT_ZEROED to indicate > > that the allocated page contents are known to be zero. > > > > Add _hints variants of the allocation functions that accept a > > pghint_t *hints output parameter: > > > > vma_alloc_folio_hints() -> folio_alloc_mpol_hints (internal) > > -> __alloc_frozen_pages_hints() > > > > The existing APIs are unchanged and continue to work without hints. > > For now, hints is always initialized to 0. A subsequent patch will > > set PGHINT_ZEROED when the page was pre-zeroed by the host. > > Why do we need this feature? Is there any performance impact? If so, > please provide some performance data.
It's in the cover letter: Performance with THP enabled on a 2GB VM, 1 vCPU, allocating 256MB of anonymous pages: metric baseline optimized delta task-clock 191 +- 31 ms 60 +- 35 ms -68% cache-misses 1.10M +- 460K 269K +- 31K -76% instructions 4.54M +- 275K 4.10M +- 130K -10% With hugetlb surplus pages: metric baseline optimized delta task-clock 183 +- 24 ms 45 +- 23 ms -76% cache-misses 1.27M +- 544K 270K +- 16K -79% instructions 5.37M +- 254K 4.94M +- 155K -8% > [snip] > > --- > Best Regards, > Huang, Ying
