Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> 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
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