Re: [PATCH] histfile: fix mmap page alignment

[Grisha Levit]

On Fri, Oct 18, 2024 at 12:15 PM Chet Ramey <chet.ramey@case.edu> wrote:
>
> On 10/18/24 11:51 AM, Chet Ramey wrote:
> > On 10/17/24 8:27 PM, Grisha Levit wrote:
> >> The mmap in history_do_write would usually fail when appending because
> >> the offset must be a multiple of the page size.
> >
> > Thanks for the report. Not everyone requires this, but since some systems
> > do, it's better to do this for portability.
>
> Of course, the fact that nothing defines HISTORY_USE_MMAP limits the
> impact somewhat.

I was just composing a question about this -- is this intentional? It looks
like it used to be behind HAVE_MMAP (which does get set) but changed soon
after.

I guess I wouldn't expect much of a performance difference between mmap-
based and regular I/O for sequential access patterns like the ones here,
though some rough testing I just did showed about a 30% improvement.