Re: [PATCH] t1050-large: replace dd by test-genrandom

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 13, 2015, 23:40 UTC
Message-ID: <xmqq4mruckrp.fsf@gitster.dls.corp.google.com>
In-Reply-To: <20150113223849.GA3144@peff.net>

Jeff King <peff@peff.net> writes:

Show 10 quoted lines

> On Tue, Jan 13, 2015 at 11:33:08PM +0100, Johannes Sixt wrote:
>
>> BTW, is it the incompressibility where the time is lost or lack of
>> sparseness of the files? How does the timing change with this patch on
>> top?
>
> Oh, good call. It's the incompressibility. Which makes perfect sense.
>
> Once we copy the file into the object database, that copy is not sparse.
> But in the genrandom version, it _is_ a million times bigger. :)

Yeah, of course ;-)

Show 24 quoted lines

> With the patch below, my timings go back to ~0.7s (actually, they seem
> slightly _better_ on average than what is in "master" now, but there is
> quite a bit of run-to-run noise, so it may not be meaningful).
>
>> diff --git a/t/t1050-large.sh b/t/t1050-large.sh
>> index f653121..9cf4e0e 100755
>> --- a/t/t1050-large.sh
>> +++ b/t/t1050-large.sh
>> @@ -9,10 +9,10 @@ test_expect_success setup '
>>  	# clone does not allow us to pass core.bigfilethreshold to
>>  	# new repos, so set core.bigfilethreshold globally
>>  	git config --global core.bigfilethreshold 200k &&
>> -	test-genrandom seed1 2000000 >large1 &&
>> +	printf "\0%2000000s" X >large1 &&
>>  	cp large1 large2 &&
>>  	cp large1 large3 &&
>> -	test-genrandom seed2 2500000 >huge &&
>> +	printf "\0%2500000s" Y >huge &&
>>  	GIT_ALLOC_LIMIT=1500k &&
>>  	export GIT_ALLOC_LIMIT
>>  '
>
> I think with this squashed in, I have no complaints at all about your
> patch.

OK, perhaps that affects the log message, so I'd play lazy and wait for a reroll.

Are we depending on the binary-ness of these test files by the way? The leading NUL \0 looked a bit strange to me.