On 4/23/26 06:31, Gregory Price wrote: > On Wed, Apr 22, 2026 at 05:20:27PM -0400, Michael S. Tsirkin wrote: >> On Wed, Apr 22, 2026 at 03:47:07PM -0400, Gregory Price wrote: >>> >>> __alloc_user_pages(..., gfp_t gfp, user_addr) >> >> With a wrapper approach, looks like we'd need something like >> __GFP_SKIP_ZERO so post_alloc_hook doesn't zero sequentially, then the >> wrapper re-zeros with folio_zero_user(). But then the wrapper needs to >> know whether the page was pre-zeroed (PG_zeroed), which is cleared by >> post_alloc_hook before return. So the information doesn't survive to >> the wrapper. >> > > I was thinking more that internally you already have that information > you need to know to skip the zeroing - and so the wrapper can just pass > __GFP_ZERO and post_alloc_hook() would do the right thing regardless > > Then on the way out, the new wrapper would take care of cacheline piece. > > However, i explored this a bit - and while it saves some churn on the > interface, it adds two paths into the buddy - and that increase in > surface might not be worth it. > > So I see the tradeoff here. The churn is probably worth it.
In v2 I commented [1] " For example, instead of changing all callers of post_alloc_hook() to pass USER_ADDR_NONE, can we make post_alloc_hook() a simple wrapper around a variant that consumes an address. So isn't there a way we can just keep the changes mostly to mm/page_alloc.c? " That should avoid most of the churn outside of page_alloc, no? [1] https://lore.kernel.org/r/[email protected] -- Cheers, David
