Re: [PATCH] Add core.trustlowlevelstat for diffs in dev,ino,uid and gid

> Linus Torvalds <torvalds@linux-foundation.org> writes:
> > On Sun, 26 Apr 2009, Junio C Hamano wrote:
> >> I like the end result.
> >>
> >> But I am not sure about dropping the nanosecond resolution timestamps.
> >> The area was extended recently in preparation for ext4; we can take
> >> advantage of it to reduce the chance the racy-git avoidance codepath
> >> triggers if we keep it.
> >>
> >>     fba2f38 (make USE_NSEC work as expected, 2009-02-19)
> >>
> >>     c06ff49 (Record ns-timestamps if possible, but do not use it without
> >>     USE_NSEC, 2009-03-04)
> >
> > Hey, we can leave the NSEC support in. Admittedly removing that was about
> > half the patch, but even with it left in, it would be a cleanup.
> 
>   I think we should have the NSEC support, as it is a performance
>   impromvent, at least on my laptop.  OK, not a huge improvment, but
>   still.
> 
>   For git version 1.6.3.rc3 I made a litle test, and the difference was
>   the following for the 'git checkout my-v2.6.25' (from my-v2.6.27):
> 
>                  for git compiled with    for git compiled without
>                  'make USE_NSEC=1 ...':   the 'USE_NSEC=1' part:
> 
>    OK open calls:       13872                   14386
>    OK close calls:      13872                   14386
>    OK mmap2 calls:        102                     649
>    OK munmap calls:        61                     608
> 
>   so, an improvment of 514 open() and close() calls, and 547 mmap2() and
>   munmap() calls, for this particular test on my particular slow laptop
>   disk.
> 
>   As I wrote in fba2f38 I would guess that the improvment is larger for
>   a faster disk, and a SSD disk should be able to see a larger
>   improvment that I did above.
> 
>   -- kjetil