At Wed, 1 Jan 2020 23:46:02 -0800, Noah Misch <n...@leadboat.com> wrote in > On Wed, Dec 25, 2019 at 10:39:32AM +0900, Kyotaro Horiguchi wrote: > > I'm not sure which is better. If we say we know that > > repalloc(AllocSetRealloc) doesn't free memory at all, there's no point > > in calling repalloc for shrinking and we could omit that under the > > name of optimization. If we say we want to free memory as much as > > possible, we should call repalloc pretending to believe that that > > happens. > > As long as we free the memory by the end of mdclose(), I think it doesn't > matter whether we freed memory in the middle of mdclose().
Agreed. > I ran a crude benchmark that found PathNameOpenFile()+FileClose() costing at > least two hundred times as much as the repalloc() pair. Hence, I now plan not > to avoid repalloc(), as attached. Crude benchmark code: I got about 25 times difference with -O0 and about 50 times with -O2. (xfs / CentOS8) It's smaller than I intuitively expected but perhaps 50 times difference is large enough. The patch looks good to me. regards. -- Kyotaro Horiguchi NTT Open Source Software Center
