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[bug#55398] [PATCH 3/3] store: Use a decaying cutoff in 'map/accumulate-
From: |
Ludovic Courtès |
Subject: |
[bug#55398] [PATCH 3/3] store: Use a decaying cutoff in 'map/accumulate-builds'. |
Date: |
Fri, 13 May 2022 17:00:44 +0200 |
This reduces the wall-clock time of:
./pre-inst-env guix system vm gnu/system/examples/desktop.tmpl -n
from 2m13s to 53s (the timings depend on which derivations have already
been built and are in store; in this case, many were missing).
* guix/store.scm (default-cutoff): New variable.
(map/accumulate-builds): Use it. Parameterize it in recursive calls to
have decaying cutoff.
---
guix/store.scm | 39 +++++++++++++++++++++++----------------
1 file changed, 23 insertions(+), 16 deletions(-)
diff --git a/guix/store.scm b/guix/store.scm
index 220901f6ce..a3240eb2e0 100644
--- a/guix/store.scm
+++ b/guix/store.scm
@@ -1362,8 +1362,12 @@ (define (build-accumulator expected-store)
(unresolved things continue)
(continue #t))))
+(define default-cutoff
+ ;; Default cutoff parameter for 'map/accumulate-builds'.
+ (make-parameter 32))
+
(define* (map/accumulate-builds store proc lst
- #:key (cutoff 30))
+ #:key (cutoff (default-cutoff)))
"Apply PROC over each element of LST, accumulating 'build-things' calls and
coalescing them into a single call.
@@ -1377,21 +1381,24 @@ (define accumulator
(build-accumulator store))
(define-values (result rest)
- (let loop ((lst lst)
- (result '())
- (unresolved 0))
- (match lst
- ((head . tail)
- (match (with-build-handler accumulator
- (proc head))
- ((? unresolved? obj)
- (if (>= unresolved cutoff)
- (values (reverse (cons obj result)) tail)
- (loop tail (cons obj result) (+ 1 unresolved))))
- (obj
- (loop tail (cons obj result) unresolved))))
- (()
- (values (reverse result) lst)))))
+ ;; Have the default cutoff decay as we go deeper in the call stack to
+ ;; avoid pessimal behavior.
+ (parameterize ((default-cutoff (quotient cutoff 2)))
+ (let loop ((lst lst)
+ (result '())
+ (unresolved 0))
+ (match lst
+ ((head . tail)
+ (match (with-build-handler accumulator
+ (proc head))
+ ((? unresolved? obj)
+ (if (>= unresolved cutoff)
+ (values (reverse (cons obj result)) tail)
+ (loop tail (cons obj result) (+ 1 unresolved))))
+ (obj
+ (loop tail (cons obj result) unresolved))))
+ (()
+ (values (reverse result) lst))))))
(match (append-map (lambda (obj)
(if (unresolved? obj)
--
2.36.0