Thanks Justin for the perspective! This 'thread' has helped me a lot in understanding some aspects of the ins and outs of using more cores and more threads.
Comer On Wed, May 25, 2016 at 6:07 PM, Justin C. Walker <jus...@mac.com> wrote: > > On May 25, 2016, at 14:42 , Adam Dershowitz wrote: > > > > > > > > >> On May 25, 2016, at 5:25 PM, Brandon Allbery <allber...@gmail.com> > wrote: > >> > >> On Wed, May 25, 2016 at 5:22 PM, Christopher Jones < > jon...@hep.phy.cam.ac.uk <mailto:jon...@hep.phy.cam.ac.uk>> wrote: > >> you don’t. Its automatic for the ports that allow it. > >> > >> And this is also true, if that was not clear. Using multiple cores is > *on by default*. You are already getting it, unless you at some point in > the past overrode buildmakejobs in macports.conf. > >> > >> -- > > > > > > You can also manually change it for a single install, for example by > using build.jobs. Such as: > > sudo port install port_whatever_name build.jobs=4 > > and then, for that specific install it will attempt to use 4 cores. > This can be handy to reduce the number of cores used, from the default, so > that you can do other things on the machine while building. > > FWIW, you can also increase the "thread count" because each core in modern > Macs provide two "hyperthreads" per core. It's almost like getting two > cores per core, but there are various architectural limitations in getting > "full throttle" performance (memory bandwidth, ...). > > Also, to see this in action, you can use the Activity Monitor, and invoke > "Window -> Floating CPU Window -> {Horizontal, Vertical, None}". This > gives you a sort of histogram view of per-hyperthread activity. > > I regularly build SageMath on Macs, and usually max out the thread count. > There can be issues with this. I've had my systems tie themselves up in > what appear to be resource knots, but I've never tracked down the real > cause (the apps I use to see what goes on get stalled when this happens). > Sometimes the system doesn't recover, but mostly, it does. > > HTH > > Justin > > -- > Justin C. Walker, Curmudgeon-At-Large > Institute for the Enhancement of the Director's Income > -------- > Experience is what you get > when you don't get what you want. > -------- > > > >
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