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authorPeter Simons <simons@cryp.to>2010-06-23T14·34+0000
committerPeter Simons <simons@cryp.to>2010-06-23T14·34+0000
commit8b7f8b56f11145c1be5188113cbcdbea27e99525 (patch)
tree06e342b8801860283f115e38a9cbafa2394f957e /doc
parent819548d92f45d8aea671ca9a3e938ff928679063 (diff)
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.
Diffstat (limited to 'doc')
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