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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/23/26 15:56, Matthew Brost wrote: > Introduce zone_appears_fragmented() as a lightweight helper to allow > subsystems to make coarse decisions about reclaim behavior in the > presence of likely fragmentation. > > The helper implements a simple heuristic: if the number of free pages > in a zone exceeds twice the high watermark, the zone is considered to > have ample free memory and allocation failures are more likely due to > fragmentation than overall memory pressure. > > This is intentionally imprecise and is not meant to replace the core > MM compaction or fragmentation accounting logic. Instead, it provides > a cheap signal for callers (e.g., shrinkers) that wish to avoid > overly aggressive reclaim when sufficient free memory exists but > high-order allocations may still fail. > > No functional changes; this is a preparatory helper for future users. > > Cc: Thomas Hellström > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: "Liam R. Howlett" > Cc: Vlastimil Babka > Cc: Mike Rapoport > Cc: Suren Baghdasaryan > Cc: Michal Hocko > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Matthew Brost > --- > include/linux/vmstat.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > index 3c9c266cf782..568d9f4f1a1f 100644 > --- a/include/linux/vmstat.h > +++ b/include/linux/vmstat.h > @@ -483,6 +483,19 @@ static inline const char *zone_stat_name(enum zone_stat_item item) > return vmstat_text[item]; > } > > +static inline bool zone_appears_fragmented(struct zone *zone) > +{ > + /* > + * Simple heuristic: if the number of free pages is more than twice the > + * high watermark, this strongly suggests that the zone is heavily > + * fragmented when called from a shrinker. > + */ > + if (zone_page_state(zone, NR_FREE_PAGES) > high_wmark_pages(zone) * 2) > + return true; > + > + return false; > +} > + > #ifdef CONFIG_NUMA > static inline const char *numa_stat_name(enum numa_stat_item item) > { Without any usage/users, this is hard to review. I don't understand the heuristic or it's logic as applied to fragmentation either. Balbir