From 8b7f8b56f11145c1be5188113cbcdbea27e99525 Mon Sep 17 00:00:00 2001 From: Peter Simons Date: Wed, 23 Jun 2010 14:34:08 +0000 Subject: Added support for passing an (impure) NIX_BUILD_CORES variable to build expressions. This patch adds the configuration file variable "build-cores" and the command line argument "--cores". These settings specify the number of CPU cores to utilize for parallel building within a job, i.e. by passing an appropriate "-j" flag to GNU Make. The default value is 1, which means that parallel building is *disabled*. If the number of build cores is specified as 0 (synonymously: "guess" or "auto"), then the actual value is supposed to be auto-detected by builders at run-time, i.e by calling the nproc(1) utility from coreutils. The environment variable $NIX_BUILD_CORES is available to builders, but the contents of that variable does *not* influence the hash that goes into the $out store path, i.e. the number of build cores to be utilized can be changed at will without requiring any re-builds. --- src/libstore/build.cc | 3 +++ 1 file changed, 3 insertions(+) (limited to 'src/libstore/build.cc') diff --git a/src/libstore/build.cc b/src/libstore/build.cc index f901c1f7d99e..a53c23bf447d 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -1411,6 +1411,9 @@ void DerivationGoal::startBuilder() in the store or in the build directory). */ env["NIX_STORE"] = nixStore; + /* The maximum number of cores to utilize for parallel building. */ + env["NIX_BUILD_CORES"] = (format("%d") % buildCores).str(); + /* Add all bindings specified in the derivation. */ foreach (StringPairs::iterator, i, drv.env) env[i->first] = i->second; -- cgit 1.4.1