Re: Git Test Coverage Report (Tuesday, Sept 25)

> On 9/27/2018 11:21 AM, Ben Peart wrote:
>>
>>
>> On 9/26/2018 2:54 PM, Derrick Stolee wrote:
>>>
>>> GIT_TEST_INDEX_THREADS=1
>>>
>>
>> Because the test repos are so small (ie smaller than 10K files), the
>> test suite already executes as if GIT_TEST_INDEX_THREADS=1 is set
>> (ie single threaded). I added the test variable so that the
>> multi-threading code could be forced to execute in spite of the
>> default minimum number of files logic.
>>
>> I'd recommend you set GIT_TEST_INDEX_THREADS=3 instead. (3 because 1
>> thread is used for loading the index extensions and we need 2 or
>> more threads available to exercise multi-threaded loading of the
>> index entries).
>
> According to t/README, GIT_TEST_INDEX_THREADS is a boolean and setting
> it to 1 causes us to use 3 threads:
>
>  GIT_TEST_INDEX_THREADS=<boolean> forces multi-threaded loading of
>  the index cache entries and extensions for the whole test suite.
>
> Here is the only consumption of the variable in the product code (in
> read-cache.c):
>
>  /* enable testing with fewer than default minimum of entries */
>  if (istate->cache_nr > 1 && nr_threads < 3 &&
> git_env_bool("GIT_TEST_INDEX_THREADS", 0))
>  nr_threads = 3;
>
> This was non-obvious to me, and I had originally set it to a larger
> number. I happened to notice the boolean nature while I was looking up
> the rest of the GIT_TEST_* variables.