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%)
