Constructor created by define-configuration is slow (>25s) when many fields are defined

Tomas Volf wrote on 9 Dec 16:13 +0100

Recipients:(address . bug-guix@gnu.org)

Message-ID:87msh499f7.fsf@wolfsden.cz

Hello,

I am writing a configuration for mpv and hit an issue of the generated

constructor (`home-mpv-configuration') is extremely slow. While the

almost 800 fields is unusually high, initializing the instances of the

record should *not* take almost 30 seconds. The full file is attached

to this email (as `mpv.scm').

Toggle snippet (6 lines)

scheme@(guix-user)> ,use (gnu home services mpv)

scheme@(guix-user)> ,t (and (home-mpv-configuration (global (mpv-profile-configuration (fullscreen #t)))) #t)

$1 = #t

;; 29.615315s real time, 50.896973s run time. 24.031723s spent in GC.

Interestingly, profiling does not give us anything useful:

Toggle snippet (4 lines)

scheme@(guix-user)> ,pr (and (home-mpv-configuration (global (mpv-profile-configuration (fullscreen #t)))) #t)

No samples recorded.

I also tried to remove all my custom sanitizers, to make sure the issue

is not in my code, but that did not help.

I took a short look, but code of both the define-configuration and of

Guix records is complex, full of syntax magic and I did not have any

luck trying to debug it myself. Hence this report.

Have a nice day,

Tomas

Attachment: mpv.scm

-- 
There are only two hard things in Computer Science:
cache invalidation, naming things and off-by-one errors.

Ludovic Courtès wrote 19 hours ago

Recipients:(name . Tomas Volf)(address . ~@wolfsden.cz)(address . 74748@debbugs.gnu.org)

Message-ID:87cyhh5eop.fsf@gnu.org

Hi,

Tomas Volf <~@wolfsden.cz> skribis:

Toggle quote (6 lines)

> I am writing a configuration for mpv and hit an issue of the generated

> constructor (`home-mpv-configuration') is extremely slow. While the

> almost 800 fields is unusually high, initializing the instances of the

> record should *not* take almost 30 seconds. The full file is attached

> to this email (as `mpv.scm').

AFAICS, time is spent in one of the compilation steps:

Toggle snippet (13 lines)scheme@(gnu home services mpv)> ,o interp #t
scheme@(gnu home services mpv)> ,t (lambda () (mpv-profile-configuration))
$13 = #<procedure 7f6ed3796700 at ice-9/eval.scm:330:13 ()>
;; 0.376347s real time, 0.375402s run time.  0.000000s spent in GC.
scheme@(gnu home services mpv)> ,o interp #f
scheme@(gnu home services mpv)> ,t (lambda () (mpv-profile-configuration))
$14 = #<procedure 7f6ec32088f8 at <unknown port>:40:3 ()>
;; 11.149828s real time, 12.052915s run time.  1.581736s spent in GC.
scheme@(gnu home services mpv)> ,t (->bool (macroexpand '(mpv-profile-configuration)))
$15 = #t
;; 0.373865s real time, 0.372698s run time.  0.000000s spent in GC.

If we look more closely, it’s the optimizing compiler that takes time;

the baseline compile (-O1) is doing okay:

Toggle snippet (16 lines)scheme@(gnu home services mpv)> ,use(system base compile)
scheme@(gnu home services mpv)> ,t (->bool (compile '(mpv-profile-configuration) #:to 'tree-il #:env (current-module)))
$20 = #t
;; 0.378741s real time, 0.377043s run time.  0.000000s spent in GC.
scheme@(gnu home services mpv)> ,t (->bool (compile '(mpv-profile-configuration) #:to 'bytecode #:env (current-module)))
$21 = #t
;; 11.946879s real time, 12.961704s run time.  1.777478s spent in GC.
scheme@(gnu home services mpv)> (define til (compile '(mpv-profile-configuration) #:to 'tree-il #:env (current-module)))
scheme@(gnu home services mpv)> ,t (->bool (compile til #:from 'tree-il #:to 'bytecode))
$22 = #t
;; 11.403420s real time, 12.317183s run time.  1.581972s spent in GC.
scheme@(gnu home services mpv)> ,t (->bool (compile til #:from 'tree-il #:to 'bytecode #:optimization-level 1))
$23 = #t
;; 0.225455s real time, 0.156137s run time.  0.000000s spent in GC.

Currently (guix build compile) applies these options to services:

((string-contains file "gnu/services/")

;; '-O2 -Ono-letrectify' compiles about ~20% faster than '-O2' for

;; large files like gnu/services/mail.scm.

(override-option #:letrectify? #f

(optimizations-for-level 2)))

I think we should at least apply this patch:

Toggle diff (14 lines)diff --git a/guix/build/compile.scm b/guix/build/compile.scm
index 5b27b55d02..f90016b9ae 100644
--- a/guix/build/compile.scm
+++ b/guix/build/compile.scm
@@ -127,7 +127,8 @@ (define (optimization-options file)
          ;; Use '-O1' to have partial evaluation and primitive inlining so we
          ;; can honor the "macro writer's bill of rights".
          (optimizations-for-level 1))
-        ((string-contains file "gnu/services/")
+        ((or (string-contains file "gnu/services/")
+             (string-contains file "gnu/home/services/"))
          ;; '-O2 -Ono-letrectify' compiles about ~20% faster than '-O2' for
          ;; large files like gnu/services/mail.scm.
          (override-option #:letrectify? #f

Would that be enough for the home-mpv configuration records you wrote?

Thanks,

Ludo’.

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