Re: mdclose() does not cope w/ FileClose() failure

At Wed, 1 Jan 2020 23:46:02 -0800, Noah Misch <[email protected]> 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