Add (guix profiling).

* guix/profiling.scm: New file.
* Makefile.am (MODULES): Add it.
* guix/store.scm (record-operation): Use 'profiled?' and
'register-profiling-hook!'.

Makefile.am

@@ -102,6 +102,7 @@ MODULES =					\
   guix/http-client.scm				\
   guix/gnupg.scm				\
   guix/elf.scm					\
+  guix/profiling.scm				\
   guix/store.scm				\
   guix/cvs-download.scm				\
   guix/svn-download.scm				\

guix/profiling.scm

@@ -0,0 +1,52 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix profiling)
+  #:use-module (ice-9 match)
+  #:export (profiled?
+            register-profiling-hook!))
+
+;;; Commentary:
+;;;
+;;; Basic support for Guix-specific profiling.
+;;;
+;;; Code:
+
+(define profiled?
+  (let ((profiled
+         (or (and=> (getenv "GUIX_PROFILING") string-tokenize)
+             '())))
+    (lambda (component)
+      "Return true if COMPONENT profiling is active."
+      (member component profiled))))
+
+(define %profiling-hooks
+  ;; List of profiling hooks.
+  (map (match-lambda
+         ("after-gc"       after-gc-hook)
+         ((or "exit" #f)   exit-hook))
+       (or (and=> (getenv "GUIX_PROFILING_EVENTS") string-tokenize)
+           '("exit"))))
+
+(define (register-profiling-hook! component thunk)
+  "Register THUNK as a profiling hook for COMPONENT, a string such as
+\"rpc\"."
+  (when (profiled? component)
+    (for-each (lambda (hook)
+                (add-hook! hook thunk))
+              %profiling-hooks)))

guix/store.scm

@@ -25,6 +25,7 @@
   #:use-module (guix base16)
   #:use-module (guix base32)
   #:use-module (guix hash)
+  #:use-module (guix profiling)
   #:autoload   (guix build syscalls) (terminal-columns)
   #:use-module (rnrs bytevectors)
   #:use-module (ice-9 binary-ports)
@@ -794,16 +795,14 @@ bytevector) as its internal buffer, and a thunk to flush this output port."
 
 (define record-operation
   ;; Optionally, increment the number of calls of the given RPC.
-  (let ((profiled (or (and=> (getenv "GUIX_PROFILING") string-tokenize)
-                      '())))
-    (if (member "rpc" profiled)
-        (begin
-          (add-hook! exit-hook show-rpc-profile)
-          (lambda (name)
-            (let ((count (or (hashq-ref %rpc-calls name) 0)))
-              (hashq-set! %rpc-calls name (+ count 1)))))
-        (lambda (_)
-          #t))))
+  (if (profiled? "rpc")
+      (begin
+        (register-profiling-hook! "rpc" show-rpc-profile)
+        (lambda (name)
+          (let ((count (or (hashq-ref %rpc-calls name) 0)))
+            (hashq-set! %rpc-calls name (+ count 1)))))
+      (lambda (_)
+        #t)))
 
 (define-syntax operation
   (syntax-rules ()