From: Stefan Beller <sbeller@google.com>
Date: Wed, 15 Nov 2017 19:14:20 GMT
Subject: Re: [PATCH] Reduce performance penalty for turned off traces
Message-ID: <CAGZ79kb4Eo0AC4Z42_ks5_+Pcy4DrDCufNb=5J=g8L6pMnHd7A@mail.gmail.com>
In-Reply-To: <20171112141737.nmnsygm4wrhtkqwb@sigill.intra.peff.net>

On Sun, Nov 12, 2017 at 6:17 AM, Jeff King <peff@peff.net> wrote:
> On Sat, Nov 11, 2017 at 07:28:58PM +0000, gennady.kupava@gmail.com wrote:
>
>> From: Gennady Kupava <gkupava@bloomberg.net>
>>
>> Signed-off-by: Gennady Kupava <gkupava@bloomberg.net>
>
> Thanks, and welcome to the list.

Welcome to the list!

> I did manually disable HAVE_VARIADIC_MACROS and confirmed that the
> result builds and passes the test suite (though I suspect that GIT_TRACE
> is not well exercised by the suite).

GIT_TRACE is exercised in the test suite (though I am not sure if it counts
as well-exercised) in t7406-submodule-update.sh for example, which uses
GIT_TRACE to obtain information about thread parallelism used by Git, as
that is not observable otherwise, if we assume that performance tests in the
standard test suite are not feasible.

> I tried timing a simple loop like:
> ....
> Without your patch, the times for GIT_TRACE=1 and GIT_TRACE=0 are about
> 500ms and 9ms respectively.
>
> After your patch, the GIT_TRACE=1 time remains the same but GIT_TRACE=0
> drops to 1ms.

So does that mean we can use a lot more tracing now?

Thanks,
Stefan