From d0840e4a2332de4f6eb4959836de569b413723c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Wed, 30 Jan 2013 18:56:20 +0100
Subject: [PATCH] derivations: Memoize `read-derivation'.
* guix/derivations.scm (read-derivation): Rename to...
(%read-derivation): ... this.
(read-derivation): New procedure.
This reduces the execution of "guix-build gdb" from 2.5s to 1.7s.
---
guix/derivations.scm | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/guix/derivations.scm b/guix/derivations.scm
index 6f73534c3cf..60d57afa12a 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -155,9 +155,8 @@ (define (derivation-built? drv sub-drvs)
inputs)
(map derivation-input-sub-derivations inputs))))))
-(define (read-derivation drv-port)
- "Read the derivation from DRV-PORT and return the corresponding
-<derivation> object."
+(define (%read-derivation drv-port)
+ ;; Actually read derivation from DRV-PORT.
(define comma (string->symbol ","))
@@ -222,6 +221,20 @@ (define (make-input-drvs x)
(loop (read drv-port)
(cons (ununquote exp) result))))))
+(define read-derivation
+ (let ((cache (make-weak-value-hash-table 200)))
+ (lambda (drv-port)
+ "Read the derivation from DRV-PORT and return the corresponding
+<derivation> object."
+ ;; Memoize that operation because `%read-derivation' is quite expensive,
+ ;; and because the same argument is read more than 15 times on average
+ ;; during something like (package-derivation s gdb).
+ (let ((file (and=> (port-filename drv-port) basename)))
+ (or (and file (hash-ref cache file))
+ (let ((drv (%read-derivation drv-port)))
+ (hash-set! cache file drv)
+ drv))))))
+
(define (write-derivation drv port)
"Write the ATerm-like serialization of DRV to PORT. See Section 2.4 of
Eelco Dolstra's PhD dissertation for an overview of a previous version of
--
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