Re: [PATCH] Put sha1dc on a diet

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 1, 2017, 22:05 UTC
Message-ID: <CAPc5daU2GVpc5Nhx13apFMs3XkL+O8_+3uA842vGQouwb4kEAg@mail.gmail.com>
In-Reply-To: <alpine.DEB.2.20.1703012227010.3767@virtualbox>

On Wed, Mar 1, 2017 at 1:56 PM, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:

Show 16 quoted lines

> Hi,
>
> On Wed, 1 Mar 2017, Junio C Hamano wrote:
>
>> Linus Torvalds <torvalds@linux-foundation.org> writes:
>>
>> > That said, I think that it would be lovely to just default to
>> > USE_SHA1DC and just put the whole attack behind us. Yes, it's slower.
>> > No, it doesn't really seem to matter that much in practice.
>>
>> Yes.  It would be a very good goal.
>
> So let me get this straight: not only do we now implicitly want to bump
> the required C compiler to C99 without any grace period worth mentioning
> [*1*], we are also all of a sudden no longer worried about a double digit
> percentage drop of speed [*2*]?

Before we get the code into shape suitable for 'next', it is more important to make sure it operates correctly, adding necessary features if any (e.g. "hash with or without check" knob) while it is in 'pu', and *1* is to allow it to progress faster without having to worry about something we could do mechanically before making it ready for 'next'.

The performance thing is really "let's see how well it goes". With effort to optimize still "just has began", I think it is too early to tell if Linus's "doesn't really seem to matter" is the case or not.

Queuing such a topic on 'pu' is one effective way to make sure people are working off of the same codebase.