On Sun, Nov 22, 2020 at 12:32:01PM -0800, Junio C Hamano wrote: > Taylor Blau <me@xxxxxxxxxxxx> writes: > > > - a geometric increase in existing size; we'll switch to 3/2 instead of > > 2 here. That's less aggressive and may help avoid fragmenting memory > > (N + 3N/2 > 9N/4, so old chunks can be reused as we scale up). > > I am sure this is something obvious to bitmap folks, but where does > 9N/4 come from (I get that the left-hand-side of the comparison is > the memory necessary to hold both the old and the new copy while > reallocating the words[] array)? I thought that I was in the group of "bitmap folks", but since it's not obvious to me either, I guess I'll have to hand in my bitmap folks membership card ;). Peff: where does 9N/4 come from? On a similar note: we could certainly use ALLOC_GROW here, too, but it would change the behavior slightly (by using alloc_nr()'s "add-16-first" behavior). Maybe we should be using it, but I'll defer to your judgement. > Thanks. Thanks, Taylor
