On 8/4/2022 10:48 PM, Derrick Stolee wrote:
> On 8/3/2022 12:51 AM, Shaoxuan Yuan wrote:
>> Enable the sparse index within the `git-rm` command.
>>
>> The `p2000` tests demonstrate a ~96% execution time reduction for
>> 'git rm' using a sparse index.
>
> Sorry that I got sidetracked yesterday when I was reviewing this
> series, but I noticed something looking at these results:
>
>> Test before after
>> -------------------------------------------------------------
>> 2000.74: git rm -f f2/f4/a (full-v3) 0.66 0.88 +33.0%
>> 2000.75: git rm -f f2/f4/a (full-v4) 0.67 0.75 +12.0%
>
> The range of _growth_ here seemed odd, so I wanted to check if this was
> due to a small sample size or not.
Yes, I do feel they are odd, as I've been checking pervious
integrations and p2000 results, they usuallly fall below 10% range.
But I was not discerning enough to name a problem :-(
>> 2000.76: git rm -f f2/f4/a (sparse-v3) 1.99 0.08 -96.0%
>> 2000.77: git rm -f f2/f4/a (sparse-v4) 2.06 0.07 -96.6%
>
> These numbers are as expected.
>
>> test_perf_on_all git read-tree -mu HEAD
>> test_perf_on_all git checkout-index -f --all
>> test_perf_on_all git update-index --add --remove $SPARSE_CONE/a
>> +test_perf_on_all git rm -f $SPARSE_CONE/a
>
> At first, I was confused why we needed '-f' and thought that maybe
> this was turning into a no-op after the first deletion. However, the
> test_perf_on_all helper does an "echo >>$SPARSE_CONE/a" before hand,
> so the file exists _in the worktree_ every time. That requires '-f'
> since otherwise Git complains that we have modifications.
Yeah, it took me some time to find out.
> However, after the first instance the file no longer exists in the
> index, so we are losing some testing of the index modification.
So true, I didn't realize at all.
> We can fix this by resetting the index in each test loop:
>
> test_perf_on_all "git rm -f $SPARSE_CONE/a && git checkout HEAD --
$SPARSE_CONE/a"
>
> Running this version of the test with GIT_PERF_REPEAT_COUNT=10 and
> using the Git repository itself, I get these numbers:
>
> Test HEAD~1 HEAD
>
--------------------------------------------------------------------------
> 2000.74: git rm ... (full-v3) 0.41(0.37+0.05) 0.43(0.36+0.07) +4.9%
> 2000.75: git rm ... (full-v4) 0.38(0.34+0.05) 0.39(0.35+0.05) +2.6%
> 2000.76: git rm ... (sparse-v3) 0.57(0.56+0.01) 0.05(0.05+0.00) -91.2%
> 2000.77: git rm ... (sparse-v4) 0.57(0.55+0.02) 0.03(0.03+0.00) -94.7%
>
> Yes, the 'git checkout' command is contributing to the overall
> numbers, but it also already has the performance improvements of
> the sparse-index, so it contributes only a little to the performance
> on the left.
>
> (Also note that the full index cases change only by amounts within
> reasonable noise. The repeat count helps there.)
New thing learned, repeat to average out noise.
--
Thanks,
Shaoxuan
