[PATCH, libfortran] PR 48587 Newunit allocator

[Janne Blomqvist]

On Tue, Oct 18, 2016 at 12:09 PM, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
> On Thu, Oct 13, 2016 at 5:16 PM, Janne Blomqvist wrote:
>> +static bool *newunits;
>
> You could make this a bitmap (like sbitmap). A bit more code but makes
> a potentially quadratic search (when opening many units) less time
> consuming.

I did think about that, yes, but decided that it wasn't worth the
extra complexity since

a) The OS typically limits the number of fd's per process to a
relatively small number (typically 1024 by default).

b) For better or worse, in libgfortran a unit is a quite big
structure, not to mention the 8 kB buffer. So obsessing over wasting
an extra 7 bits per unit seemed pointless.

c) Due to the newunit_lwi, in many scenarios it should be able to skip
scanning over, if not all then at least most of, the in-use units. Of
course, it's possible to design a scenario which defeats the lwi, but,
is that something real software does? And even if it does, due to a)
above I think the effect would be quite modest anyway.



-- 
Janne Blomqvist