Constant MysQL crashes. How to fix? MysQL is frequently going down. Error logs contain:

[ERROR] Missing system table mysql.proxies_priv; please run mysql_upgrade to create it  | 149 occurrences
[ERROR] Native table 'performance_schema'... has the wrong structure                    | 500+


I did a research on the internet. It is suggested to fix it by running a mysql_upgrade script like this:

/etc/init.d/mysqld stop
mysqld_safe --skip-grant-tables &amp;
mysql_upgrade
/etc/init.d/mysqld stop
/etc/init.d/mysqld start


It is strongly advised to create a backup before running any upgrades. But my databases do not look healthy. 

There is no snapshot option for this server.

Questions:


How do I preserve the information?
How would I go about it?
Is it okay to do mysqldumps for such databases?
So I finally fixed it. 

I ran upgrade script as described in question.

The logs complained only about the wrong structure of performance_schema which is a system database that contains only performance metrics and a missing proxies_priv table inside other system database. 

The errors are gone.

And of course before making any changes I did a backup of all databases with mysqldump. 

Thank you all for help! :)