Messages in this thread | | | Date | Sun, 14 Nov 2004 14:15:49 -0800 (PST) | From | Brad Fitzpatrick <> | Subject | 2.6.9: unkillable processes during heavy IO |
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We have two database servers which freeze up during heavy IO load. The machines themselves are responsible, but the mysqld processes are forever locked, unkillable with even kill -9. I can't restart with MySQL without rebooting the machines.
I can reasonable rule out hardware, since this is happening in the same way on two identical machines.
I'd like to know how I can debug this, to file a proper bug report.
The hardware/software stack is:
- Dual Opteron 246, SMP kernel, w/ NUMA - 9 GB of memory (4GB in one zone, 5GB in the other) - MySQL, running mostly InnoDB, but some MyISAM - MegaRAID raid-10 - device mapper - XFS (used as both O_DIRECT from InnoDB and regularly from MyISAM)
At this point I'm going to try changing different variables on different machines in order to try and isolate it, but it's a slow process.
- on raw partions, instead of device mapper - ext3 instead of XFS - not using O_DIRECT
"Screenshot":
roast:~# killall -9 mysqld roast:~# killall -9 mysqld roast:~# ps afx | grep mysqld 31495 ? D 0:08 /usr/local/mysql/bin/mysqld --defaults-extra-file=/usr/local/mysql/data/my.cnf --basedir=/usr/local/mysql/ --datadir=/data/mydb --user=root --pid-file=/var/run/mysqld/mysqld.pid --skip-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock 32391 ? D 0:01 /usr/local/mysql/bin/mysqld --defaults-extra-file=/usr/local/mysql/data/my.cnf --basedir=/usr/local/mysql/ --datadir=/data/mydb --user=root --pid-file=/var/run/mysqld/mysqld.pid --skip-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock 515 ? D 0:00 /usr/local/mysql/bin/mysqld --defaults-extra-file=/usr/local/mysql/data/my.cnf --basedir=/usr/local/mysql/ --datadir=/data/mydb --user=root --pid-file=/var/run/mysqld/mysqld.pid --skip-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock 517 ? Z 0:00 \_ [mysqld] <defunct>
Next time it hangs like this, how can I get a kernel backtrace or other useful information for a certain process?
Thanks!
- Brad
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