![]() May 31 stĪnother couple of stalls, again several minutes long.Īround lunchtime, I power down the machine in another attempt at resetting the SMC and remember to run the Apple hardware test afterward (which finds nothing). ![]() I start culling login items and hunting down launchd entries. SyncThing, by the way, is also running but shows no significant CPU or I/O usage (unlike OneDrive, it is not prone to just randomly fire up and start scanning my hard disk). I also see no mds_stores, corespotlightd, suggestd or photoanalysisd above 5% CPU, so by this point, I’m starting to think that OneDrive is at least part of the problem since I’ve had to throttle its CPU usage more than once and it is pretty much crap on macOS. I spend another full minute trying to launch Macs Fan Control, force the fans on again and it apparently makes a difference, as I see CPU temperature drop from 70 oC to 65 oC. I can only see OneDrive and kernel_task hogging the CPU, so I kill the former. I manage to launch Activity Monitor (easily a 1m affair under these conditions) and search for culprits. So this is what happened since my original post: May 30 thĪlmost one full day after the initial cleaning, I had another 8-10m stall. This is annoying because I’ve always strived to have an absolutely silent office, but when things are OK it’s quieter than what little street noise comes through the windows. I now have mine set to start at 40 oC and max out at 75 oC, which ensures the fans are always slightly above Apple’s defaults. Halfway through this rigmarole, I went and got iStat Menus off the App Store (which I picked because I didn’t like their direct licensing terms).Įven though that does not do fan control, I’ve also had the free version of Macs Fan Control around for a couple of years since it does basic temperature monitoring, so I can force the fans on and configure a single basic response “curve” (more of a hard line, really) based on CPU package temperature. I am using both Thunderbolt ports for external displays (an aging, purple-edged 4K Superfine and an HDMI adapter to a non-retina LG UltraWide), but there seems to be hardly any GPU impact.Īnd despite it being early Summer and temperatures starting to rise above 25 oC, the prime suspect was my recent upgrade to macOS Big Sur 11.4 (20F71). It’s probably important to point out that this is a 2017 27-inch iMac with an Intel i5 CPU and 24GB of RAM, sporting a Radeon 570 and the ungodly nuisance of a 1TB Fusion Drive.Ĭleaning out the machine, resetting the SMC or using AC to keep the environment cool seemed to help at first, but I had a hard time atributing this to be thermal throttling. I was getting random stalls on my iMac, with kernel_task taking up anywhere between 90-350% CPU without apparent cause ever since I upgraded to Big Sur 11.4. I may update this post (again) later if I have more details, but for now let’s start with the whats and hows: Context It annoys me to no end that I only noticed this was an issue due to my having tried to pick my network when doing Internet Recovery, which helped pin things down. * The year-on-year changes to Console.app (and the glacial slowness of the machine when stalling) made it very hard to spot patterns in logs.Īnd, of course, I have to get work done, so working through all the possible permutations was very slow. * The Wi-Fi icon was moved from the menu bar into Control Center (so status changes and error flashes are invisible). * I have a Gigabit Ethernet connection (so I only have Wi-Fi on for Continuity). But the reason I failed to notice this over the course of two weeks of trial and error troubleshooting is manifold: ![]() Summary: Every time I try to join that network, kernel_task immediately goes into a spin lock burning CPU cycles across all cores and stalling the machine, with variations of these two lines in the logs: ARPT: 2859.550473: wlc_phy_rx_iq_est_acphy: SPINWAIT ERROR : IQ measurement timed outĪRPT: 2859.550487: wl0: fatal error, reinitializing, total count of reinit's, Learned: I should have been even more systematic. Update, three weeks after the Big Sur 11.4 upgrade: Long story short, my current working theory is that 11.4 rendered my Wi-Fi card unable to associate to my 5GHz network (which is all based on Apple Airport Extremes), and that there is a macOS kernel bug that handles this situation very poorly.
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