High CPU usage due to contracts

[srcreigh]

Thanks for the easy to use lib @zyrolasting .

I'm a racket noob so go easy on me.

The file-watchers package dominates my CPU (99% CPU for any process that uses it). I tried both intensive-watch and robust-watch. I ran a quick profiling script and seems like 99.9% of the time is spent checking contracts. Using the defaults.

I may look into this further but thought I'd ping you now in case you have some tips.

#lang racket/base

(require file-watchers
         profile)

(profile-thunk (λ ()
                 (define th (watch (list (find-system-path 'orig-dir))
                                   displayln displayln
                                   robust-watch))
                 (sleep 10)
                 (kill-thread th))
               #:threads #t)

outputs:

====================================================================================
                               Caller
 Idx   Total       Self      Name+src                                         Local%
       ms(pct)     ms(pct)     Callee
====================================================================================
 [1] 3454(99.9%)    0(0.0%)  loop ...cket/7.6/pkgs/file-watchers/main.rkt:56:21
                               ??? [3]                                        100.0%
------------------------------------------------------------------------------------
 [2]    1(0.0%)     0(0.0%)  repl-thunk ...-20200403.1450/racket/repl.rkt:267:6
                               call-with-expanded-syntax-caching-evaluator [4]100.0%
------------------------------------------------------------------------------------
                               loop [1]                                       100.0%
 [3] 3454(99.9%) 3454(99.9%) ??? ...contract/private/arrow-val-first.rkt:486:18
------------------------------------------------------------------------------------
                               repl-thunk [2]                                 100.0%
 [4]    1(0.0%)     0(0.0%)  call-with-expanded-syntax-caching-evaluator ...0:0
                               ??? [5]                                        100.0%
------------------------------------------------------------------------------------
                               call-with-expanded-syntax-caching-evaluator [4]100.0%
 [5]    1(0.0%)     0(0.0%)  ??? ...lects/racket/private/more-scheme.rkt:261:28
                               run-module-instance! [6]                       100.0%
------------------------------------------------------------------------------------
                               ??? [5]                                        100.0%
 [6]    1(0.0%)     0(0.0%)  run-module-instance! (unknown source)
                               for-loop [7]                                   100.0%
------------------------------------------------------------------------------------
                               run-module-instance! [6]                       100.0%
 [7]    1(0.0%)     0(0.0%)  for-loop (unknown source)
                               temp35_0 [8]                                   100.0%
------------------------------------------------------------------------------------
                               for-loop [7]                                   100.0%
 [8]    1(0.0%)     0(0.0%)  temp35_0 (unknown source)
                               [running body] [9]                             100.0%
------------------------------------------------------------------------------------
                               temp35_0 [8]                                   100.0%
 [9]    1(0.0%)     0(0.0%)  [running body] ...ane/Code/ado/src/server.rkt":##f
                               profile-thunk [10]                             100.0%
------------------------------------------------------------------------------------
                               [running body] [9]                             100.0%
[10]    1(0.0%)     0(0.0%)  profile-thunk ...are/pkgs/profile-lib/main.rkt:9:0
                               run [11]                                       100.0%
------------------------------------------------------------------------------------
                               profile-thunk [10]                             100.0%
[11]    1(0.0%)     0(0.0%)  run ...t v7.6/share/pkgs/profile-lib/main.rkt:39:2
                               temp2 [12]                                     100.0%
------------------------------------------------------------------------------------
                               run [11]                                       100.0%
[12]    1(0.0%)     1(0.0%)  temp2 /Users/shane/Code/ado/src/server.rkt:12:15
------------------------------------------------------------------------------------

[zyrolasting]

Thanks for raising this. The contracts are not checking complicated structures, although one of them does consult the filesystem. I'm not sure if that would cause a CPU spike.

The profile actually alerted me to a loop that spins when it should be yielding time to other threads. I'll just need to rewrite some code to better leverage synchronizeable events.