On Mon, Jul 8, 2013 at 2:13 PM, John Baldwin <j...@freebsd.org> wrote: > On Monday, July 08, 2013 2:23:31 am Garrett Cooper wrote: >> On Sun, Jul 7, 2013 at 7:25 PM, Garrett Cooper <yaneurab...@gmail.com> > wrote: >> > On Jul 7, 2013, at 2:15 PM, Alfred Perlstein <alf...@freebsd.org> wrote: >> > >> >> On 7/7/13 2:01 PM, Garrett Cooper wrote: >> >>> Why the magic number 12? >> >> >> >> Numbers higher seem to result in worse performance as reported by some > members of my team. >> > >> > The suggestion is good in spirit, but this doesn't justify the reasoning > for this recommendation for all cases. >> > >> > Please revert this change and add a doc page or notes to the dev handbook > discussing what the empirical process and results were for determining this > value so people can come up with their own values that work best with their > hardware and software config. This recommendation is prone to bitrot like some > of the recommendations in tuning(7). >> > >> > Misinformation is sometimes more harmful than no information. >> >> I spoke with Alfred over the phone and did some more careful thought >> about this and I'm rescinding this request. >> >> Alfred did a good job at documenting how JFLAG works (it was >> previously undocumented). My concern over -j12 was performance >> related, and after giving things more careful thought it actually >> makes sense why -j12 was chosen because Westmere and newer processors >> have issues with NUMA and cache locality between multiple processor >> packages as we've seen non-empirically and empirically at Isilon with >> FreeBSD 7 and 10 (it's a known issue that jeffr@ and jhb@ are aware >> of). >> >> I'll come up with a concise patch that does what Alfred was trying to >> achieve and have Alfred review it. >> >> Thanks (and thank you Alfred for the contribution!!!)! > > Westmere is fine, it's post-Westmere that is more troublesome.
Even the 6-core Westmeres (I'm being completely dumb here as you and Jeff know a lot more about the NUMA issue than I do as I just caught the tail end of the conversation at BSDCan)? I'm asking because they (iX) are using build.ix as the primary build machine and it has 2 Westmere dies with (IIRC -- please correct me if I'm wrong Alfred/Xin/etc) 6 cores each and are SMT enabled. It also has a boatload of RAM and disks hooked up to an mfi(4) controller (which could be a contributing factor in the performance degradation issue). > I think the comment is not super useful, but don't object enough to want > it to be removed. I always use 'make tinderbox' instead of > 'make universe' though as I want build failures to be obvious. For the > described use case of "checking if kernels build", 'tinderbox' certainly > seems to be the more appropriate target. Changing it from universe to tinderbox seems like a better idea -- I'll put a short note in my proposed patch for that. Thanks! -Garrett _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
