On 12/10/21 8:10 PM, Dexuan Cui wrote: >> From: Jens Axboe <axboe@xxxxxxxxx> >> Sent: Friday, December 10, 2021 6:05 PM >> ... >> It's more likely the real fix is avoiding the repeated plug list scan, >> which I guess makes sense. That is this commit: >> >> commit d38a9c04c0d5637a828269dccb9703d42d40d42b >> Author: Jens Axboe <axboe@xxxxxxxxx> >> Date: Thu Oct 14 07:24:07 2021 -0600 >> >> block: only check previous entry for plug merge attempt >> >> If that's the case, try 5.15.x again and do: >> >> echo 2 > /sys/block/<dev>/queue/nomerges >> >> for each drive you are using in the IO test, and see if that gets >> rid of the excess CPU usage. >> >> -- >> Jens Axboe > > Thanks for the reply! Unluckily this does not work. > > I tried the below command: > > for i in `ls /sys/block/*/queue/nomerges`; do echo 2 > $i; done > > and verified that the "nomerges" are changed to "2", but the > excess CPU usage can still reproduce easily. Just out of curiosity, can you do: # perf record -a -g -- sleep 3 when you see the excessive CPU usage, then attach the output of # perf report -g to a reply? How confident are you in your bisect result? -- Jens Axboe
