Created attachment 304686 [details] journal with 6.4.4 where the high iowait time is present After update to kernel 6.4.4 one of the cores is showing high iowait percentage. $ mpstat -P ALL Linux 6.4.4-stable-1 (lenovo2) 22/07/23 _x86_64_ (8 CPU) 21:55:25 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 21:55:25 all 2.31 0.00 0.76 11.98 0.19 0.04 0.00 0.00 0.00 84.71 21:55:25 0 2.51 0.00 0.77 0.08 0.11 0.04 0.00 0.00 0.00 96.50 21:55:25 1 1.89 0.00 0.59 0.05 0.38 0.04 0.00 0.00 0.00 97.05 21:55:25 2 2.43 0.00 0.80 0.07 0.09 0.03 0.00 0.00 0.00 96.59 21:55:25 3 2.05 0.00 0.57 94.46 0.07 0.04 0.00 0.00 0.00 2.81 21:55:25 4 2.57 0.01 0.77 0.06 0.09 0.03 0.00 0.00 0.00 96.47 21:55:25 5 2.62 0.00 1.20 0.08 0.14 0.04 0.00 0.00 0.00 95.92 21:55:25 6 2.29 0.00 0.83 0.98 0.13 0.11 0.00 0.00 0.00 95.66 21:55:25 7 2.14 0.00 0.59 0.05 0.48 0.02 0.00 0.00 0.00 96.71 Downgrading the kernel back to 6.4.3 the problem disappears. I am running Arch Linux, and a thread on the Arch Linux forums yielded a bisection that identified the commit that is the likely cause of this issue: A 6.4.4 kernel built with bd4f737b145d85c7183ec879ce46b57ce64362e1 reverted also fixes the issue.
This is the same issue as in https://bugzilla.kernel.org/show_bug.cgi?id=217699
Reported as https://lore.kernel.org/lkml/12251678.O9o76ZdvQC@natalenko.name/
I confirm this is resolved for me running kernel 6.4.4 built with commit bd4f737b145d85c7183ec879ce46b57ce64362e1 reverted.
The LKML thread linked to this BZ indicates that the high cpu utilisation in cpu monitors is incorrect display and that the kernel is performing correctly even when iowait is high for mariadbd running.
The LKML thread linked to this BZ indicates that the high cpu utilisation in cpu monitors is incorrect display and that the kernel is performing correctly even when iowait is high for mariadbd running. In that case the original commit should be retained.
Would you be able to test the patch from here: [1]? [1] https://lore.kernel.org/lkml/11ded843-ac08-2306-ad0f-586978d038b1@kernel.dk/raw
*** This bug has been marked as a duplicate of bug 217699 ***
Tested kernel 6.4.6 built with the referenced patch, and the anomalous 100% cpu activity on a single core is no longer displayed in the System Monitor widget, and mpstat no longer shows >94% io-wait. So this resolves the issue for my systems.