SnoopPrecompile + Refactoring of update sysinfo

[carstenbauer]

Used SnoopPrecompile to improve precompilation / runtime a little bit (see below). Moved maybe_gather_sysinfo() (now replaced by update_sysinfo!) to __init__() so that once the package is loaded (using ThreadPinning) we can be certain to have the system information of the currently used system/node.

Test:

@time begin
    @time_imports using ThreadPinning
    @showtime threadinfo()
    @showtime pinthreads(:compact)
    @showtime getcpuids()
    @showtime pinthread(0)
    @showtime getcpuid()
    @showtime ncores()
end

Before the PR:

2.4 ms  ThreadPinning
threadinfo(): 1.639246 seconds (5.44 M allocations: 281.975 MiB, 3.00% gc time, 97.34% compilation time)
pinthreads(:compact): 0.410707 seconds (974.82 k allocations: 49.977 MiB, 3.24% gc time, 99.54% compilation time)
getcpuids(): 0.000181 seconds (399 allocations: 34.625 KiB)
pinthread(0): 0.002169 seconds (653 allocations: 41.452 KiB, 98.21% compilation time)
getcpuid(): 0.001729 seconds (31 allocations: 1.531 KiB, 99.61% compilation time)
ncores(): 0.029779 seconds (95.94 k allocations: 5.013 MiB, 99.95% compilation time)
  2.163364 seconds (6.57 M allocations: 340.419 MiB, 2.89% gc time, 97.14% compilation time)

With the PR:

0.5 ms  SnoopPrecompile
919.5 ms  ThreadPinning 87.73% compilation time
threadinfo(): 0.434676 seconds (686.07 k allocations: 34.318 MiB, 1.35% gc time, 95.83% compilation time)
pinthreads(:compact): 0.266147 seconds (15.00 k allocations: 824.570 KiB, 99.71% compilation time)
getcpuids(): 0.000259 seconds (397 allocations: 34.562 KiB)
pinthread(0): 0.002079 seconds (144 allocations: 9.680 KiB, 98.53% compilation time)
getcpuid(): 0.001734 seconds (31 allocations: 1.531 KiB, 99.64% compilation time)
ncores(): 0.017690 seconds (897 allocations: 44.359 KiB, 99.94% compilation time)
  1.771727 seconds (3.64 M allocations: 188.919 MiB, 1.62% gc time, 89.38% compilation time)

The overall gain is nice but not huge (expected because dynamically parsing lscpu output takes a good chunk of the time). Most importantly though, we improved the time it takes to run threadinfo and pinthreads and co at the cost of increased using ThreadPinning time.

[carstenbauer]

Update

0.5 ms  SnoopPrecompile
875.1 ms  ThreadPinning 86.52% compilation time
threadinfo(): 0.392547 seconds (288.25 k allocations: 14.257 MiB, 2.54% gc time, 86.13% compilation time)
pinthreads(:compact): 0.294755 seconds (15.00 k allocations: 824.445 KiB, 99.43% compilation time)
getcpuids(): 0.000213 seconds (401 allocations: 34.688 KiB)
pinthread(0): 0.002098 seconds (144 allocations: 9.680 KiB, 97.99% compilation time)
getcpuid(): 0.001744 seconds (31 allocations: 1.531 KiB, 99.62% compilation time)
ncores(): 0.017941 seconds (897 allocations: 44.359 KiB, 99.93% compilation time)
  1.670321 seconds (2.60 M allocations: 135.224 MiB, 1.99% gc time, 88.84% compilation time)