Re: [RFC/PATCH v2 1/1] cygwin: Add fast_lstat() and fast_fstat() functions

On 2013-07-18 19.50, Ramsay Jones wrote:

Mark Levedahl wrote:

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On 07/15/2013 10:06 PM, Torsten Bögershausen wrote:

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On 2013-07-15 21.49, Junio C Hamano wrote:

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Mark Levedahl [off-list ref] writes:

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In order to limit the adverse effects caused by this implementation,
we provide a new "fast stat" interface, which allows us to use this
only for interactions with the index (i.e. the cached stat data).

Signed-off-by: Ramsay Jones <redacted>
---

I've tested this on Cygwin 1.7 on WIndows 7 , comparing to the results
using your prior patch (removing the Cygwin specific lstat entirely)
and get the same results with both, so this seems ok from me.

My comparison point was created by reverting your current patch from
pu, then reapplying your earlier patch on top, so the only difference
was which approach was used to address the stat functions.

Caveats:
1) I don't find any speed improvement of the current patch over the
previous one (the tests actually ran faster with the earlier patch,
though the difference was less than 1%).

Hm, measuring the time for the test suite is one thing,
did you measure the time of "git status" with and without the patch?

(I don't have my test system at hand, so I can test in a few days/weeks)

Timing for 5 rounds of "git status" in the git project. First, with the 
current fast_lstat patches:
/usr/local/src/git>for i in {1..5} ; do time git status >& /dev/null ; done

real    0m0.218s
user    0m0.000s
sys     0m0.218s

real    0m0.187s
user    0m0.077s
sys     0m0.109s

real    0m0.187s
user    0m0.030s
sys     0m0.156s

real    0m0.203s
user    0m0.031s
sys     0m0.171s

real    0m0.187s
user    0m0.062s
sys     0m0.124s

Now, with Ramsay's original patch just removing the non-Posix stat 
functions:
/usr/local/src/git>for i in {1..5} ; do time git status >& /dev/null ; done

real    0m0.218s
user    0m0.046s
sys     0m0.171s

real    0m0.187s
user    0m0.015s
sys     0m0.171s

real    0m0.187s
user    0m0.015s
sys     0m0.171s

real    0m0.187s
user    0m0.047s
sys     0m0.140s

real    0m0.187s
user    0m0.031s
sys     0m0.156s


I see no difference in the above. (Yes, I checked multiple times that I 
was using different executables).

Hmm, that looks good. :-D

Torsten reported a performance boost using the win32 stat() implementation
on a linux git repo (2s -> 1s, if I recall correctly) on cygwin 1.7.
Do you have a larger repo available to test?

(I have a 5 years old Dual Core, 2.5 Ghz, 1 TB hard disk, Win XP, cygwin 1.7)
On that machine I can see the performance boost.
Which kind of computers are you guys using?

SSD/hard disk ?
How much RAM ?
Which OS ?
Is there a difference between Win XP, Win7, Win8?

[snip]