Owen, ----- Original Message ----- From: "Owen Scott Medd" <[EMAIL PROTECTED]> To: "Heikki Tuuri" <[EMAIL PROTECTED]> Cc: ""Nicholas Gaugler"" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Wednesday, October 09, 2002 5:44 PM Subject: Re: mysqld Threads with Innobase
> [ start stupid question ] > > Does setting innodb_thread_concurrency to 1 imply that only one innodb > thread will be working at any given time? So using this on SMP servers > that you would like to be answering simultaneous queries is probably not > what you would really like to be doing, no? > > [ end stupid question ] only one thread is then allowed inside the InnoDB backend concurrently. But the threads also do work in the MySQL interpreter, and more importantly, in communication with the corresponding client application threads. Since 'thread thrashing' lowers performance 100-fold, also drastic measures like setting the InnoDB concurrency to 1 should be tried. Unfortunately, it does not usually help. The thrashing happens then outside the InnoDB backend. > Owen Regards, Heikki > On Wed, 2002-10-09 at 02:55, Heikki Tuuri wrote: > > Nicholas, > > > > ----- Original Message ----- > > From: ""Nicholas Gaugler"" <[EMAIL PROTECTED]> > > Newsgroups: mailing.database.mysql > > Sent: Wednesday, October 09, 2002 8:22 AM > > Subject: mysqld Threads with Innobase > > > > > > > I know it's not very important in normal day to day operations, but does > > > anyone know what each thread does within mysqld with Innobase installed? > > > It'd be nice to know what Innobase is doing when a process is pinned at > > 100% > > > of the cpu..if it's doing cleanup from a huge update, etc. > > > > > /usr/local/sqldrive/mysql-4.0.4-beta/bin/mysqld --defaults-extra-file=/usr/l > > > ocal/sqldrive/mysql-4.0.4-beta/data/my > > > 1682 ttyp1 S 0:00 > > > > > /usr/local/sqldrive/mysql-4.0.4-beta/bin/mysqld --defaults-extra-file=/usr/l > > > ocal/sqldrive/mysql-4.0.4-beta/data/my > > > > ... > > > > only one thread, the main thread, does background cleaning operations. You > > can see from SHOW INNODB STATUS what the main thread is currently doing. > > > > It is a good idea to tell the id of that thread in the printout of SHOW > > INNODB STATUS. I will add it to 4.0.5. > > > > In your case there are lots of threads eating up 100 % of CPU. If the > > performance is very slow, this looks like yet another case of Linux 'thread > > thrashing' which is plaguing both MyISAM and InnoDB tables under certain > > loads. It is a clear performace bug in Linux or glibc, and we are working to > > find a fix or a workaround to that problem. > > > > You can try setting > > > > set-variable = innodb_thread_concurrency = 1 > > > > in my.cnf to remove the thread thrashing. That helps in some cases > > > > > Thanks! > > > > > > nickg > > > > Best regards, > > > > Heikki Tuuri > > Innobase Oy > > --- > > InnoDB - transactions, hot backup, and foreign key support for MySQL > > See http://www.innodb.com, download MySQL-Max from http://www.mysql.com --------------------------------------------------------------------- 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
