On Fri, Sep 28, 2012 at 06:45:24AM -0400, Benoit Jacob wrote: > 2012/9/28 Aryeh Gregor <a...@aryeh.name>: > > On Thu, Sep 27, 2012 at 6:08 PM, Gregory Szorc <g...@mozilla.com> wrote: > >> I actually held out on you with the initial landing of mach: there is more > >> advanced tree building code in the pipes, complete with progress > >> indicators. > >> However, getting it reviewed is a challenge because we want the build > >> system > >> integration to be right. When that lands, mach will be smart enough to > >> automatically define make flags optimal for your machine. e.g. -j == # of > >> cores. So, you get optimal/parallel builds with no configuration necessary. > >> This will all be configurable, of course. > > > > Is -j equal to number of cores really optimal? I've always been told > > that it's better to set it to more like twice the number of cores, > > because some fraction of threads will normally be stalled on I/O and > > you don't want cores idle. > > Depending on various factors, this can be offset by other factors like > cores competing for limited resources such as CPU cache. On my core i7 > with 8 logical cores and 8M cache and a SSD, -j8 is fastest. More > generally while building a C++ project (C++ is computationally > expensive to compile) you're not very likely to be IO bound, > especially with a SSD. A C project might be different.
On my core i7, -j12 is fastest. bigger values are marginally slower but they are all faster than -j8. Mike _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
