Hi,
On 2021-07-25 19:07:18 +0300, Yura Sokolov wrote: > I've dreamed to write more compact structure for vacuum for three > years, but life didn't give me a time to. > > Let me join to friendly competition. > > I've bet on HATM approach: popcount-ing bitmaps for non-empty elements. My concern with several of the proposals in this thread is that they over-optimize for this specific case. It's not actually that crucial to have a crazily optimized vacuum dead tid storage datatype. Having something more general that also performs reasonably for the dead tuple storage, but also performs well in a number of other cases, makes a lot more sense to me. > (Bad radix result probably due to smaller cache in notebook's CPU ?) Probably largely due to the node dispatch. a) For some reason gcc likes jump tables too much, I get better numbers when disabling those b) the node type dispatch should be stuffed into the low bits of the pointer. > select prepare(1000000, 2, 100, 1); > > attach size shuffled > array 6ms 12MB 53.42s > intset 23ms 16MB 54.99s > rtbm 115ms 38MB 8.19s > tbm 186ms 100MB 8.37s > vtbm 105ms 59MB 9.08s > radix 64ms 42MB 10.41s > svtm 73ms 10MB 7.49s > Test4 > > select prepare(1000000, 100, 1, 1); > > attach size shuffled > array 304ms 600MB 75.12s > intset 775ms 98MB 47.49s > rtbm 356ms 38MB 4.11s > tbm 539ms 100MB 4.20s > vtbm 493ms 42MB 4.44s > radix 263ms 42MB 6.05s > svtm 360ms 8MB 3.49s > > Therefore Specialized Vaccum Tid Map always consumes least memory amount > and usually faster. Impressive. Greetings, Andres Freund
