Sorry to spam the group, but I just noticed that I asserted we were on a 2.4 kernel -- we're on 2.6.9-11 as part of CentOS 4.1...
-JF > -----Original Message----- > From: Heikki Tuuri [mailto:[EMAIL PROTECTED] > Sent: Sunday, October 16, 2005 2:23 AM > To: mysql@lists.mysql.com > Subject: Re: Non-linear degradation in bulk loads? > > Jon, > > your hardware/OS combination is quite new and unusual. It > might indeed be an OS problem. We observed from a 64-bit RHEL > 4 that when the file cache of the OS grew bigger than 4 GB, > then the file I/O performance dropped to one tenth of the > normal. You would not expect that kind of behavior from a 64-bit OS. > > When you see the slowdown, what does 'top' say about the OS > file cache size? > > " > The database is our main sites database but we've > dramatically reduced the load on that machine over the past > couple months through careful optimization of our code. The > box is a dual, dual-core Opteron, 8GB of RAM running a 32-bit > Linux 2.4 kernel and MySQL 4.0.20 (32-bit of course). We > have 1GB allocated to the buffer pool, and our usual 1GB * > 3 log files. 8 I/O threads. > > Load on the box sits at around 6-7, with a large (>50%) > amount of time spent in wait state, but actual disk > throughput to our software RAID array (No longer on a SAN...) > is quite low -- 6-9k blocks/s out, 1-6k blocks/s in. > " > > Regards, > > Heikki > > > ----- Original Message ----- > From: ""Jon Frisby"" <[EMAIL PROTECTED]> > Newsgroups: mailing.database.myodbc > Sent: Friday, October 14, 2005 10:39 PM > Subject: RE: Non-linear degradation in bulk loads? > > > > I've tried tweaking the structure of the schema to have, > for example, a = > > PRIMARY KEY index on email, no other indexes, and then > insert in sorted = > > order -- made no improvement whatsoever. Another clue that > leads me to = > > believe that this may be an OS issue: Starting a large cp > on the same = > > box (from a local filesystem other than the one the InnoDB > data pool was = > > on, to NFS) caused MySQL to become COMPLETELY backlogged > (we went from = > > ~15-20 connections at any given instant to 750 (our > max_connections = > > setting)). > > > > -JF > > > > > >> -----Original Message----- > >> From: Heikki Tuuri [mailto:[EMAIL PROTECTED] > >> Sent: Wednesday, October 12, 2005 8:15 AM > >> To: mysql@lists.mysql.com > >> Subject: Re: Non-linear degradation in bulk loads? > >>=20 > >> Jon, > >>=20 > >> hmm... maybe one of the indexes inevitably is in a random order. > >>=20 > >> Please post a typical > >>=20 > >> SHOW INNODB STATUS\G > >>=20 > >> when the inserts happen slowly. > >>=20 > >> What is your my.cnf like? > >>=20 > >> Regards, > >>=20 > >> Heikki > >> Innobase/Oracle > >>=20 > >> ----- Alkuper=E4inen viesti ----- > >> L=E4hett=E4j=E4: "Jon Frisby" <[EMAIL PROTECTED]> > >> Vastaanottaja: "Heikki Tuuri" <[EMAIL PROTECTED]>;=20 > >> <mysql@lists.mysql.com> > >> L=E4hetetty: Wednesday, October 12, 2005 3:08 AM > >> Aihe: RE: Non-linear degradation in bulk loads? > >>=20 > >>=20 > >> > Two solutions: 1) sort the rows to be inserted on the > key 'email'=20 > >> > before inserting. > >> > > >> > 2) Or: > >> > > >> > http://dev.mysql.com/doc/mysql/en/innodb-tuning.html > >> > " > >> > If you have UNIQUE constraints on secondary keys, starting=20 > >> from MySQL > >> > 3.23.52 and 4.0.3, you can speed up table imports by > temporarily=20 > >> > turning off the uniqueness checks during the import session: > >> > SET UNIQUE_CHECKS=3D0; > >> > > >> > For big tables, this saves a lot of disk I/O because > InnoDB can use=20 > >> > its insert buffer to write secondary index records in a batch. > >> > " > >> > > >> > But make sure you do not have any duplicates in the rows! > >>=20 > >> After sending my mail, I discovered SET UNIQUE_CHECKS=3D0, and=20 > >> subsequent to that it also occurred to me to try putting the=20 > >> data in in sorted order. Unfortunately, doing=20 > >> UNIQUE_CHECKS=3D0 did not work, and even the combination of=20 > >> both did not work. First chunk (3.4m rows) was ~1.5 minutes,=20 > >> second was ~5 minutes... > >>=20 > >> At this point I'm inclined to believe that there is something=20 > >> very wrong with the disk subsystem because of this and other=20 > >> problems (doing a large cp from the datapool filesystem to=20 > >> another filesystem brought the database to a near-halt, among=20 > >> other things). > >>=20 > >> As a stop-gap solution, I created the table with no indexes,=20 > >> and loaded all the data (loaded in linear time), and plan on=20 > >> doing a CREATE UNIQUE INDEX on the table. Will this happen=20 > >> in linear time, or near-linear time? > >>=20 > >> *sigh* > >>=20 > >> -JF=20 > >>=20 > >>=20 > >> -- > >> MySQL General Mailing List > >> For list archives: http://lists.mysql.com/mysql > >> To unsubscribe: =20 > >> http://lists.mysql.com/[EMAIL PROTECTED] > >>=20 > >>=20 > > > > -- > > MySQL General Mailing List > > For list archives: http://lists.mysql.com/mysql > > To unsubscribe: > > http://lists.mysql.com/[EMAIL PROTECTED] > > > > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: > http://lists.mysql.com/[EMAIL PROTECTED] > > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
