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. > Thoughts? >
