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Added support for passing an (impure) NIX_BUILD_CORES variable to build expressions.

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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.
This commit is contained in:
Peter Simons 2010-06-23 14:34:08 +00:00
parent 819548d92f
commit 8b7f8b56f1
5 changed files with 35 additions and 0 deletions
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3
src/libstore/build.cc
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@ -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;

1
src/libstore/globals.cc
View file

@ -22,6 +22,7 @@ bool keepGoing = false;
bool tryFallback = false;
Verbosity buildVerbosity = lvlInfo;
unsigned int maxBuildJobs = 1;
unsigned int buildCores = 1;
bool readOnlyMode = false;
string thisSystem = "unset";
time_t maxSilentTime = 0;

5
src/libstore/globals.hh
View file

@ -55,6 +55,11 @@ extern Verbosity buildVerbosity;
/* Maximum number of parallel build jobs. 0 means unlimited. */
extern unsigned int maxBuildJobs;
/* Number of CPU cores to utilize in parallel within a build, i.e. by passing
this number to Make via '-j'. 0 means that the number of actual CPU cores on
the local host ought to be auto-detected. */
extern unsigned int buildCores;
/* Read-only mode. Don't copy stuff to the store, don't change the
database. */
extern bool readOnlyMode;