This patch intends to fix the recent bugzilla [1] report where the kworker flush thread seemed to be taking 100% CPU utilizationa and was slowing down the whole system. The backtrace indicated that we were stuck in mballoc allocation path. The issue was only seen kernel 6.5+ and when ext4 was mounted with -o stripe (or stripe option was implicitly added due us mkfs flags used). Although I was not able to fully replicate this issue, from the perf probe logs collected I have a possible root cause which I have explained in the patch commit message. Now, the one thing I'm still skeptical about is why this was only seen in kernel 6.5+. We added a new mballoc criteria in kernel 6.5 but I was not able to find a satisfactory explanation as to why that would have any effect here. Furter, the issue still persisted when I asked one of the reporters to disable the it using sysfs file and rerun the test. Maybe there are some more factors at play? Anyways, I would appreciate if the people experiencing this issue can help test this patch and see if it fixes the regression. [1] https://bugzilla.kernel.org/show_bug.cgi?id=217965 Regards, ojaswin Ojaswin Mujoo (1): ext4: fallback to complex scan if aligned scan doesn't work fs/ext4/mballoc.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) -- 2.39.3
