Re: [gentoo-portage-dev] [PATCH 1/3] Add caching to catpkgsplit function

[Chun-Yu Shei]

Awesome!  Here's a patch that adds @lru_cache to use_reduce, vercmp, and
catpkgsplit.  use_reduce was split into 2 functions, with the outer one
converting lists/sets to tuples so they can be hashed and creating a
copy of the returned list (since the caller seems to modify it
sometimes).  I tried to select cache sizes that minimized memory use increase,
while still providing about the same speedup compared to a cache with
unbounded size. "emerge -uDvpU --with-bdeps=y @world" runtime decreases
from 44.32s -> 29.94s -- a 48% speedup, while the maximum value of the
RES column in htop increases from 280 MB -> 290 MB.

"emerge -ep @world" time slightly decreases from 18.77s -> 17.93, while
max observed RES value actually decreases from 228 MB -> 214 MB (similar
values observed across a few before/after runs).

Here are the cache hit stats, max observed RES memory, and runtime in
seconds  for various sizes in the update case.  Caching for each
function was tested independently (only 1 function with caching enabled
at a time):

catpkgsplit:
CacheInfo(hits=1222233, misses=21419, maxsize=None, currsize=21419)
270 MB
39.217

CacheInfo(hits=1218900, misses=24905, maxsize=10000, currsize=10000)
271 MB
39.112

CacheInfo(hits=1212675, misses=31022, maxsize=5000, currsize=5000)
271 MB
39.217

CacheInfo(hits=1207879, misses=35878, maxsize=2500, currsize=2500)
269 MB
39.438

CacheInfo(hits=1199402, misses=44250, maxsize=1000, currsize=1000)
271 MB
39.348

CacheInfo(hits=1149150, misses=94610, maxsize=100, currsize=100)
271 MB
39.487


use_reduce:
CacheInfo(hits=45326, misses=18660, maxsize=None, currsize=18561)
407 MB
35.77

CacheInfo(hits=45186, misses=18800, maxsize=10000, currsize=10000)
353 MB
35.52

CacheInfo(hits=44977, misses=19009, maxsize=5000, currsize=5000)
335 MB
35.31

CacheInfo(hits=44691, misses=19295, maxsize=2500, currsize=2500)
318 MB
35.85

CacheInfo(hits=44178, misses=19808, maxsize=1000, currsize=1000)
301 MB
36.39

CacheInfo(hits=41211, misses=22775, maxsize=100, currsize=100)
299 MB
37.175


I didn't bother collecting detailed stats for vercmp, since the
inputs/outputs are quite small and don't cause much memory increase.
Please let me know if there are any other suggestions/improvements (and
thanks Sid for the lru_cache suggestion!).

Thanks,
Chun-Yu