Re: [PATCH v2] fetch-pack: grow stateless RPC windows exponentially

[Jonathan Tan <jonathantanmy@google.com>]

On Tue, Jul 19, 2016 at 9:46 AM, Stefan Beller <sbeller@google.com> wrote:
> Care to elaborate on why you choose 11/10 as growth factor?
>
> (As someone who has a tick in micro optimizing:
> 9/8 is roughly the same exponent, but the division
> by 8 is easier as it is just a shift by 3. Similar 17/16)

I don't have a specific reason for 11/10 as opposed to, say, 9/8 - I
think that the time taken to execute this line is negligible compared
to what's done in the calling code, but I'll change it to 9/8 if there
is another reason for me to send another patch.

> I guess one design criterion was 10 being a round number?
> Does it make sense to experiment with the factor at all?
> Digging into that, LARGE_FLUSH originates from 6afca450c3f,
> (2011-03-20, fetch-pack: progressively use larger handshake windows),
> and before we only had a linear growth.
>
> So I guess what I do not understand is why we need to slow down the
> exponential growth at all?

The current code has an exponential (a' = a * 2) then a linear (a' = a
+ 1024) growth. I'm not slowing down the exponential growth - that
part is retained. I'm replacing the linear growth with another
conservative exponential growth (a' = a * 11 / 10).