Re: snprintf.c hammering memset()

Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2018-10-01 19:52:40 -0400, Tom Lane wrote:
>> Ouch indeed. Quite aside from cycles wasted, that's way more stack than
>> we want this to consume. I'm good with forcing this to 16 or so ...
>> any objections?

> Especially after your performance patch, shouldn't we actually be able
> to get rid of that memset entirely?

That patch takes the memset out of the main line, but it'd still be
a performance problem for formats using argument reordering; and the
stack-space concern would remain the same.

> And if not, shouldn't we be able to reduce the per-element size of
> argtypes considerably, by using a uint8 as the base, rather than 4 byte
> per element?

argtypes is only a small part of the stack-space issue, there's also
argvalues which is (at least) twice as big. I don't think second-guessing
the compiler about the most efficient representation for an enum is
going to buy us much here.

regards, tom lane