cython() slow on Cygwin

[embray]

At least on the latest release build I did, running the cython() function is extremely slow, even for compiling a trivial function, taking up to a minute on my system.

sage: %timeit cython('def foo(): pass')
48.3 s ± 497 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

While I recall it being slower on Cygwin than on Linux (almost anything that involves running a subprocess is) I don't recall it ever being this slow.

Depends on #31344

Component: porting: Cygwin

Keywords: cygwin cython

Issue created by migration from https://trac.sagemath.org/ticket/31187

[embray]

comment:1

One observation is that every time I call cython() the CPU usage of "Windows Defender Antivirus Service" spikes.

[embray]

comment:2

It seems to be sage.env.cython_aliases that's responsible for this, as it makes many pkgconfig calls each time using a subprocess, and is called every time cythonize() is called. ISTM it should be possible to cache the results of this call; maybe even run it in the background after Sage starts.

[embray]

comment:3

For reference this is definitely responsible for the majority of this overhead:

sage: %timeit sage.env.cython_aliases()
48.6 s ± 1.97 s per loop (mean ± std. dev. of 7 runs, 1 loop each)

[embray]

comment:4

Another idea would be to run this as a post-install step it is already run when building Sage, so if its results can be cached and included in the Sage installation that would solve the problem.

[mkoeppe]

Dependencies: #31344

[mkoeppe]

comment:5

#31344 caches the results of sage.env.cython_aliases; more work is taking place in #31365, #31384

[mkoeppe]

comment:6

Sage development has entered the release candidate phase for 9.3. Setting a new milestone for this ticket based on a cursory review of ticket status, priority, and last modification date.