Date: Sun, 20 Aug 2017 07:19:29 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 221029] AMD Ryzen: strange compilation failures using poudriere or plain buildkernel/buildworld Message-ID: <bug-221029-8-KphQRQd0G6@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-221029-8@https.bugs.freebsd.org/bugzilla/> References: <bug-221029-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D221029 --- Comment #80 from Don Lewis <truckman@FreeBSD.org> --- The events controlled by kern.sched.balance are timer based and are probably much less frequent than occurences of a CPU running out of work to do and triggering a steal_idle event unless the machine has a very high load avera= ge so that all of the CPUs have long queues of runnable processes. Since I do= n't really care about scheduling fairness in these experiments, I'm planning on leaving kern.sched.balance=3D0. I think that kern.sched.steal_idle is much= more interesting. In order to make the experiments as meaningful as possible, I= 'd like to keep the overall CPU idle time as low as possible. If there is a l= ot of CPU idle time with kern.sched.steal_idle=3D0, then the reduction of memo= ry bandwidth demand and lower die temperature can confuse the results. Based on my previous experiment, I suspect that steal_idle events ignore the CPU affinity time setting, which sort of makes sense. In my latest experiment, I set kern.sched.affinity=3D10 and set both steal_= idle and balance back to 0. This time ghc successfully built, which I attribute= to a lucky roll of the dice. During the lang/ghc build, ghc (either the boots= trap or newly built version) gets executing a number of times. How many times it succeeds before eventually getting a SIGBUS seems random. What is somewhat surprising is that once built, ghc was able to successfully able to build a large number of hs_* ports without any failures. This time chromium also avoided the rename issue and built successfully. The only failure was lang= /go, which has also failed frequently on my Ryzen machine. I think the lang/ghc= and lang/go issues are distinct with the other random build problems. What would be interesting would be to dig into sched_ule and tweak steal_id= le to restrict the CPUs that it can steal tasks from. One experiment would be= to only allow it to steal from the other thread on the same CPU core. Another would be to only allow it to steal from a core in the same CCX. --=20 You are receiving this mail because: You are the assignee for the bug.=
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