05/11: gexp: Cache the module to derivation mappings.

[guix-commits]

civodul pushed a commit to branch master
in repository guix.

commit f5fca9a82cec76d2e10b8b6c96be2dd79f638ba0
Author: Ludovic Courtès <address@hidden>
Date:   Sun Oct 27 19:12:11 2019 +0100

    gexp: Cache the module to derivation mappings.
    
    This reduces the number of 'add-data-to-store' cache lookups from 3329
    to 2743 (hit rate: 27% to 11%) when running:
    
      GUIX_PROFILING=add-data-to-store-cache guix build libreoffice -nd
    
    Execution time of "guix build libreoffice -nd" goes from 1.86s to 1.80s.
    
    * guix/gexp.scm (imported+compiled-modules): Wrap body in 'mcached'.
---
 guix/gexp.scm | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/guix/gexp.scm b/guix/gexp.scm
index fa74e80..b640c07 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -660,21 +660,24 @@ names and file names suitable for the 
#:allowed-references argument to
                                     (module-path %load-path))
   "Return a pair where the first element is the imported MODULES and the
 second element is the derivation to compile them."
-  (mlet %store-monad ((modules  (if (pair? modules)
-                                    (imported-modules modules
-                                                      #:system system
-                                                      #:module-path 
module-path)
-                                    (return #f)))
-                      (compiled (if (pair? modules)
-                                    (compiled-modules modules
-                                                      #:system system
-                                                      #:module-path module-path
-                                                      #:extensions extensions
-                                                      #:guile guile
-                                                      #:deprecation-warnings
-                                                      deprecation-warnings)
-                                    (return #f))))
-    (return (cons modules compiled))))
+  (mcached equal?
+           (mlet %store-monad ((modules  (if (pair? modules)
+                                             (imported-modules modules
+                                                               #:system system
+                                                               #:module-path 
module-path)
+                                             (return #f)))
+                               (compiled (if (pair? modules)
+                                             (compiled-modules modules
+                                                               #:system system
+                                                               #:module-path 
module-path
+                                                               #:extensions 
extensions
+                                                               #:guile guile
+                                                               
#:deprecation-warnings
+                                                               
deprecation-warnings)
+                                             (return #f))))
+             (return (cons modules compiled)))
+           modules
+           system extensions guile deprecation-warnings module-path))
 
 (define* (lower-gexp exp
                      #:key