On Thu, May 14, 2026 at 10:48:28AM -0400, Michael S. Tsirkin wrote: > On Thu, May 14, 2026 at 07:51:03AM -0400, Gregory Price wrote: > > On Tue, May 12, 2026 at 05:05:16PM -0400, Michael S. Tsirkin wrote: > > > When a reported free page is split via expand() to satisfy a > > > smaller allocation, the sub-pages placed back on the free lists > > > lose the PageReported flag. This means they will be unnecessarily > > > re-reported to the hypervisor in the next reporting cycle, wasting > > > work. > > > > > > While I was unable to quantify the performance difference, it is > > > an obvious waste, even if small. > > > > > > Propagate the PageReported flag to sub-pages during expand(), > > > both in page_del_and_expand() and try_to_claim_block(), so > > > that they are recognized as already-reported. > > > > > > Signed-off-by: Michael S. Tsirkin <[email protected]> > > > Assisted-by: Claude:claude-opus-4-6 > > ... snip ... > > > @@ -1731,9 +1740,10 @@ static __always_inline void > > > page_del_and_expand(struct zone *zone, > > > int high, int migratetype) > > > { > > > int nr_pages = 1 << high; > > > + bool was_reported = page_reported(page); > > > > > > __del_page_from_free_list(page, zone, high, migratetype); > > > - nr_pages -= expand(zone, page, low, high, migratetype); > > > + nr_pages -= expand(zone, page, low, high, migratetype, was_reported); > > > account_freepages(zone, -nr_pages, migratetype); > > > } > > > > > > > Maybe mildly out of scope but worth asking: Are there other flags that > > should be retained/propogated on a split? If so, rather than pass > > was_reported, should we just take a temporary copy of the page flags and > > pass them all in? > > > > ~Gregory > > > Not that I can see, no. >
You do this exact thing again later :] https://lore.kernel.org/linux-mm/9a22e0f9bbe1278913754db6df76e291a006181a.1778616612.git....@redhat.com/ ~Gregory
