----- Original Message ----- From: "gerald_clark" <[EMAIL PROTECTED]> Wrote:
> Perhaps each process simply requires 8 seconds of disk access. > Since they share the same disk it will take 8sec. times the number of > processes > running to complete. > > You have a strange definition of "hang". > > Claus Reestrup wrote: > > >Hi! > > > >I have a problem with MySQL that hangs when concurrent queries run. > > > >The symptom is this: > >A) A Perl program that performs several queries using temporary tables takes 8 >seconds to run. > >CPU utilisation around 30% (using the 'top' command) > > > >B) Running two instances of the same perl program in parallel causes each program >to "wait for each other", doubling the response > >time for each program, that is each program is now 16 seconds to finish. > >CPU utilisation around 40% (using the 'top' command) > >Lets call them process 1 and process 2, each started at the same time. > >They both run for 16 seconds and they both finish at the same time. > > > >C) Doubling the amount of processes again, running 4 in parallel, shows the same >symptom: > >They are all started at the same time, and they all return results at the same time. > >Each process is now 32 seconds to finish > >CPU utilisation around 60% (using the 'top' command) > > > >etc. > >etc. > > > >This shows that all processes seem to wait for each other to finish before >returning a result instead of returning the results > >immediately! > > > >Has anyone solved this problem before? > > > > > > > >SERVER INFO: > >----------------------------- > >* MySQL v 3.23.52 on FreeBSD 4.7, dual 1200 MHz Intel CPU, 1Gb RAM, 10Gb Free swap >space > >* and lots of free space on all partitions, especially in /var > >* no limits on CPU, Memory, open files etc. in FreeBSD kernel > >* No errors shown in /var/messages > >* No errors shown in /var/db/mysql/host.err > >* The queries involve the use of temporary tables and a lot of READ queries on >regular tables. > >* No locks have been issued and no locks are needed. > >* No other processes on the server uses MySQL while the program runs. > > > > > >/etc/my.cnf: > >[mysqld] > >port = 3306 > >socket = /tmp/mysql.sock > >skip-locking > >skip-innodb > >set-variable = max_tmp_tables=1024 > >set-variable = tmp_table_size=128M > >set-variable = key_buffer=384M > >set-variable = max_heap_table_size=128M > >set-variable = max_allowed_packet=16M > >set-variable = join_buffer_size=4M > >set-variable = long_query_time=3 > >set-variable = table_cache=4096 > >set-variable = sort_buffer=32M > >set-variable = record_buffer=16M > >set-variable = thread_cache=16 > >set-variable = max_connections=300 > ># Try number of CPU's*2 for thread_concurrency > >set-variable = thread_concurrency=4 > >set-variable = myisam_sort_buffer_size=64M > >server-id = 1 > > > ># Point the following paths to different dedicated disks > >tmpdir = /home0/mysqltmp/ > > > > > > > >--------------------------------------------------------------------- > >Before posting, please check: > > http://www.mysql.com/manual.php (the manual) > > http://lists.mysql.com/ (the list archive) > > > >To request this thread, e-mail <[EMAIL PROTECTED]> > >To unsubscribe, e-mail ><[EMAIL PROTECTED]> > >Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > > > > > > > > > > > > --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
