On Thu, Oct 02, 2014 at 05:51:29PM +0100, Chris Tapp wrote: > > On 2 Oct 2014, at 11:04, Burton, Ross <ross.bur...@intel.com> wrote: > > > On 2 October 2014 10:36, Oliver Novakovic <oliver.novako...@alpine.de> > > wrote: > >> Can anyone recommend a reasonable performant hardware setup to use ? > >> > >> What should be considered ? Are there any pitfalls ? What about bottlenecks > >> in the build system ?
you should start by saying what you're going to build, my experience is quite different when building "small" images like console-image or even x11-image and "big" images/feeds which contain whole qt5 stack, 3 webkits and 2 chromium builds. In general: bitbake will better utilize all available performance with bigger image (e.g. build time for console image won't change so much if you go from 8 cores to 24, but building e.g. just webkit alone will be more than twice faster on 24 cores). Regards, > >> Specifically: > >> > >> How many cores are recommended ? And how much cache is necessary ? > >> How much of the main memory does Yocto really use ? Is 32 GB sufficient or > >> should I go for 64 ? > >> > >> Does it make sense to use two SSDs as Raid0 to get builds faster ? > > > > As much of everything as you can afford. :) The build isn't heavy in > > any particular metric, so don't sacrifice RAM for SSDs for example. > > > > RAID 0 over SSD would be nice and fast, but I prefer having a good > > amount of RAM and a tuned ext4 (no journal, long commit delay) so data > > doesn't actually hit the disk as frequently. Keeping the actual build > > directories on a separate disk is good for performance and not causing > > data loss when you lose a disk. > > > > There are people that have 64GB in machines and then set TMPDIR to a > > tmpfs. Surprisingly this isn't that much faster (5% or so), but it's > > a lot easier on the hardware and power consumption. > > My experience: > > I've got a quad core with hyper-threading (so 8 usable cores) running at > about 3.8 GHz, 16GB of RAM and use multiple SSDs - one to hold the meta data, > downloads and top level build areas (local.conf, etc) and have the TMPDIR on > a second SSD (so, as Ross says, I don't get a surprise when it wears out!). > > I can build my images (basically an x11 image) in just under 60 minutes (once > all the files have been fetched). I run with BB_NUMBER_THREADS and > PARALLEL_MAKE both set to 16 to make sure the cores are fully loaded as much > as possible (other says that should be 8 and 8 to reduce scheduling overhead). > > During the build the system is CPU bound quite a bit of the time (so more > cores should help), but there are significant periods where the build > dependency chain means this isn't the case and only two or three cores are > active. Previously I recall comparing results with someone else and finding > that having lots more cores (24, I think) didn't give a significant > improvement in build time (certainly not for the 3x system build cost). > > I've never seen peak memory usage go much above 9 GB during a build, and the > peaks generally coincide with linking activities for "big" items (gcc, > eglibc). This is likely to go higher with more active threads. > > I started out with a RAID-0 SSD build array, but I didn't really see any > difference over a single high-spec (consumer) SSD. As Ross said, running a > fast file system on the disk is a good idea. > > -- > > Chris Tapp > opensou...@keylevel.com > www.keylevel.com > > ---- > You can tell you're getting older when your car insurance gets real cheap! > > -- > _______________________________________________ > yocto mailing list > yocto@yoctoproject.org > https://lists.yoctoproject.org/listinfo/yocto -- Martin 'JaMa' Jansa jabber: martin.ja...@gmail.com
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