Re: [PATCH RESEND 0/8] hugetlb: add demote/split page functionality
From: Michal Hocko <mhocko@suse.com>
Date: 2021-09-13 15:51:09
Also in:
lkml
On Fri 10-09-21 17:11:05, Mike Kravetz wrote: [...]
quoted hunk ↗ jump to hunk
@@ -5064,8 +5068,18 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask) if (did_some_progress > 0 && should_compact_retry(ac, order, alloc_flags, compact_result, &compact_priority, - &compaction_retries)) + &compaction_retries)) { + /* + * In one pathological case, pages can be stolen immediately + * after reclaimed. It looks like we are making progress, and + * compaction_retries is not incremented. This could cause + * an indefinite number of retries. Cap the number of retries + * for costly orders. + */ + if (max_tries && tries > max_tries) + goto nopage; goto retry; + }
I do not think this is a good approach. We do not want to play with retries numbers. If we want to go with a minimal change for now then the compaction feedback mechanism should track the number of reclaimed pages to satisfy watermarks and if that grows beyond reasonable (proportionaly to the request size) then simply give up rather than keep trying again and again. -- Michal Hocko SUSE Labs