Re: [PATCH 6.4 800/800] io_uring: Use io_schedule* in cqring wait

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On 7/23/23 11:31, Jens Axboe wrote:
...
Just read the first one, but this is very much expected. It's now just
correctly reflecting that one thread is waiting on IO. IO wait being
100% doesn't mean that one core is running 100% of the time, it just
means it's WAITING on IO 100% of the time.


Seems reasonable thank you.

Question - do you expect the iowait to stay high for a freshly created mariadb doing nothing (as far as I can tell anyway) until process exited? Or Would you think it would drop in this case prior to the process exiting.

For example I tried the following - is the output what you expect?

Create a fresh mariab with no databases - monitor the core showing the iowaits with:

   mpstat -P ALL 2 100

# rm -f /var/lib/mysql/*
# mariadb-install-db --user=mysql --basedir=/usr --datadir=/var/lib/mysql

# systemctl start mariadb (iowaits -> 100%)

# iotop -bo |grep maria        (shows no output, iowait stays 100%)

(this persists until mariadb process exits)


# systemctl stop mariadb (iowait drops to 0%)







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