On Wed, 20 Jan 2021, Vlastimil Babka wrote: > On 1/19/21 8:26 PM, David Rientjes wrote: > > On Mon, 18 Jan 2021, Charan Teja Reddy wrote: > > > >> should_proactive_compact_node() returns true when sum of the > >> weighted fragmentation score of all the zones in the node is greater > >> than the wmark_high of compaction, which then triggers the proactive > >> compaction that operates on the individual zones of the node. But > >> proactive compaction runs on the zone only when its weighted > >> fragmentation score is greater than wmark_low(=wmark_high - 10). > >> > >> This means that the sum of the weighted fragmentation scores of all the > >> zones can exceed the wmark_high but individual weighted fragmentation > >> zone scores can still be less than wmark_low which makes the unnecessary > >> trigger of the proactive compaction only to return doing nothing. > >> > >> Issue with the return of proactive compaction with out even trying is > >> its deferral. It is simply deferred for 1 << COMPACT_MAX_DEFER_SHIFT if > >> the scores across the proactive compaction is same, thinking that > >> compaction didn't make any progress but in reality it didn't even try. > > > > Isn't this an issue in deferred compaction as well? It seems like > > deferred compaction should check that work was actually performed before > > deferring subsequent calls to compaction. > > Direct compaction does, proactive not. > > > In other words, I don't believe deferred compaction is intended to avoid > > checks to determine if compaction is worth it; it should only defer > > *additional* work that was not productive. > > Yeah, that should be more optimal. > Charan, is this something you'd like to follow up on, or should I take a look instead? Thanks!
