Pat Farrell;247157 Wrote:
>
> Threads do, processes don't. I don't know which MySql uses.
Mysql uses threads. The obvious sign is that the memory usage for all
is exactly the same. Processes would show some variation in size.
These are processes:
Code:
--------------------
postfix 30307 0.0 0.3 8764 3996 ? S 11:04 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 30411 0.0 0.3 8632 3968 ? S 11:04 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 30417 0.0 0.3 8500 3816 ? S 11:04 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 31844 0.0 0.3 8632 3828 ? S 11:06 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 31932 0.0 0.3 8236 3388 ? S 11:06 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 31935 0.0 0.3 8632 3944 ? S 11:06 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 32009 0.0 0.3 8500 3764 ? S 11:07 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
postfix 32095 0.0 0.3 8632 3972 ? S 11:07 0:00 smtpd -n
smtp -t inet -u -o smtpd_sasl_auth_enable yes
--------------------
the memory size varies a ton. Mysql, however, doesn't vary a bit in
size:
Code:
--------------------
mysql 946 0.0 4.2 84040 10792 ? S Aug21 0:00
/usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql
--pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306
--socket=/var/run/mysqld/mysqld.sock
mysql 947 0.0 4.2 84040 10792 ? S Aug21 0:00
/usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql
--pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306
--socket=/var/run/mysqld/mysqld.sock
mysql 948 0.0 4.2 84040 10792 ? S Aug21 0:00
/usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql
--pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306
--socket=/var/run/mysqld/mysqld.sock
mysql 949 0.0 4.2 84040 10792 ? S Aug21 0:00
/usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql
--pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306
--socket=/var/run/mysqld/mysqld.sock
--------------------
And those have been running for months, yet all precisely the same size
because they are all addressing the exact same memory. Changing a
global in one changes it in all of them (the nature of threads which is
either a blessing or a curse depending on if you remember the memory is
shared).
>
> Even if its a few thousand bytes each, who cares.
> Memory is cheap. $30 for 512MB means under $0.30 per megabyte.
True, but at only a couple hundred bytes for a process table entry it
is even less to worry about. Let it have two dozen threads and your
memory usage wouldn't be any different.
--
snarlydwarf
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