RE: Slow Response -- What Does This Sound Like to You?

[Vikas Shukla]

Hi everybody,

I think we need to focus on three things:-

A) temp tables created on disk
B) table cache size
C) buffer sizes

If you find the number of temp tables created on disk is very large, please 
increase the temp_table_size.

Enable the slow query log And check if sort buffer size and join buffer size 
needss to be increased if multiple joins are used.

Also check whether the tables used in the slow queries do have index build on 
them or not. This heavily impacts the performance. If not create index on 
frequently used tables.

Please try the above and let us know if resolved.

Regards 

Vikas shukla 

-Original Message-
From: "Rick James" 
Sent: ‎10-‎05-‎2013 07:24
To: "Bruce Ferrell" ; "mysql@lists.mysql.com" 

Subject: RE: Slow Response -- What Does This Sound Like to You?

1. MyISAM locks _tables_.  That can cause other connections to be blocked.  
Solution: switch to InnoDB.  Caution:  There are a few caveats when switching; 
see
https://kb.askmonty.org/en/converting-tables-from-myisam-to-innodb/

2. As mentioned by Shawn, the Query Cache can be more trouble than it is worth. 
 However 90 seconds cannot be blamed on the QC.  Still, shrink it or turn it 
off:
* If frequently writing to tables, turn it off (type=OFF _and_ size=0)
* If less frequently, then decide which queries will benefit, add SQL_CACHE to 
them, set type=DEMAND and size=50M (no larger).

3. Meanwhile, try to make that long query more efficient.  Can you show it to 
us, together with SHOW CREATE TABLE, SHOW TABLE STATUS, and EXPLAIN ?

> -Original Message-
> From: Bruce Ferrell [mailto:bferr...@baywinds.org]
> Sent: Thursday, May 09, 2013 6:05 PM
> To: mysql@lists.mysql.com
> Subject: Re: Slow Response -- What Does This Sound Like to You?
> 
> On 05/09/2013 03:25 PM, Robinson, Eric wrote:
> >>
> >>> -Original Message-
> >>> From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
> >>> Sent: Thursday, May 09, 2013 1:58 PM
> >>> To: mysql@lists.mysql.com
> >>> Subject: Slow Response -- What Does This Sound Like to You?
> >>>
> >>> We have a situation where users complain that the system
> >> periodically
> >>> freezes for 30-90 seconds. We check the slow query logs and
> >> find that
> >>> one user issued a complex query that did indeed take 30-90
> >> seconds to
> >>> complete. However, NO slow queries are recorded for the other 50
> >>> users, before, during, or after the freeze. Note that the complex
> >>> query in question always shows: "Lock_time: 0".
> >>>
> >>> Q: What conditions could cause single query to lock up a
> >> database for
> >>> a while for all users (even though it shows "lock time: 0")  but no
> >>> other slow queries would show in the logs for any other
> >> users who are
> >>> hitting the database at the same time?
> >>>
> >>> OS: RHEL3 x64
> >>> CPU: 8 x 2.9GHz Xeon
> >>> RAM: 32GB
> >>> Disk: RAID 5 (6 x 512GB SSD)
> >>> MySQL: 5.0.95 x64
> >>> Engine: MyISAM
> >>>
> >
> >
> >> MyISAM?  Or InnoDBm to have been finished Lock_time perhaps applies
> >> only to table locks on MyISAM.
> >>
> >> SHOW ENGINE InnoDB STATUS;
> >> You may find some deadlocks.
> >>
> >> Is Replication involved?
> >>
> >> Anyone doing an ALTER?
> >
> >
> >
> > MyISAM, no replication involved, and nobody is altering the database.
> This happens whenever people run certain reports.
> >
> >
> > --Eric
> 
> One thing I'd look at to start is the error log, if enabled.  After
> that, I'd look at running mysqltuner to get a look at statistics before
> and after one of these events.  I know there are those who prefer the
> Percona toolkit, but those pull lots raw stats and offers little in
> terms of suggestions... Unless you wish to engage Percona.
> 
> Be aware, there are two versions of mysqltuner.  The one I use is found
> at http://mysqltuner.pl.  I know, it's old, but it at least runs.  The
> newer one doesn't seem to have been brought to completion.
> 
> You might want to enable the slow query option that logs queries that
> execute without indexes.  They can be real killers.  Reports that use
> views often cause this as views become complex joins under the hood
> that can easily miss your indexes resulting in full table scans.
> 
> 
> --
> MySQL General Mailing List
> For list archives: http://lists.mysql.com/mysql
> To unsubscribe:http://lists.mysql.com/mysql


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RE: Slow Response -- What Does This Sound Like to You?

[Rick James]

1. MyISAM locks _tables_.  That can cause other connections to be blocked.  
Solution: switch to InnoDB.  Caution:  There are a few caveats when switching; 
see
https://kb.askmonty.org/en/converting-tables-from-myisam-to-innodb/

2. As mentioned by Shawn, the Query Cache can be more trouble than it is worth. 
 However 90 seconds cannot be blamed on the QC.  Still, shrink it or turn it 
off:
* If frequently writing to tables, turn it off (type=OFF _and_ size=0)
* If less frequently, then decide which queries will benefit, add SQL_CACHE to 
them, set type=DEMAND and size=50M (no larger).

3. Meanwhile, try to make that long query more efficient.  Can you show it to 
us, together with SHOW CREATE TABLE, SHOW TABLE STATUS, and EXPLAIN ?

> -Original Message-
> From: Bruce Ferrell [mailto:bferr...@baywinds.org]
> Sent: Thursday, May 09, 2013 6:05 PM
> To: mysql@lists.mysql.com
> Subject: Re: Slow Response -- What Does This Sound Like to You?
> 
> On 05/09/2013 03:25 PM, Robinson, Eric wrote:
> >>
> >>> -Original Message-
> >>> From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
> >>> Sent: Thursday, May 09, 2013 1:58 PM
> >>> To: mysql@lists.mysql.com
> >>> Subject: Slow Response -- What Does This Sound Like to You?
> >>>
> >>> We have a situation where users complain that the system
> >> periodically
> >>> freezes for 30-90 seconds. We check the slow query logs and
> >> find that
> >>> one user issued a complex query that did indeed take 30-90
> >> seconds to
> >>> complete. However, NO slow queries are recorded for the other 50
> >>> users, before, during, or after the freeze. Note that the complex
> >>> query in question always shows: "Lock_time: 0".
> >>>
> >>> Q: What conditions could cause single query to lock up a
> >> database for
> >>> a while for all users (even though it shows "lock time: 0")  but no
> >>> other slow queries would show in the logs for any other
> >> users who are
> >>> hitting the database at the same time?
> >>>
> >>> OS: RHEL3 x64
> >>> CPU: 8 x 2.9GHz Xeon
> >>> RAM: 32GB
> >>> Disk: RAID 5 (6 x 512GB SSD)
> >>> MySQL: 5.0.95 x64
> >>> Engine: MyISAM
> >>>
> >
> >
> >> MyISAM?  Or InnoDBm to have been finished Lock_time perhaps applies
> >> only to table locks on MyISAM.
> >>
> >> SHOW ENGINE InnoDB STATUS;
> >> You may find some deadlocks.
> >>
> >> Is Replication involved?
> >>
> >> Anyone doing an ALTER?
> >
> >
> >
> > MyISAM, no replication involved, and nobody is altering the database.
> This happens whenever people run certain reports.
> >
> >
> > --Eric
> 
> One thing I'd look at to start is the error log, if enabled.  After
> that, I'd look at running mysqltuner to get a look at statistics before
> and after one of these events.  I know there are those who prefer the
> Percona toolkit, but those pull lots raw stats and offers little in
> terms of suggestions... Unless you wish to engage Percona.
> 
> Be aware, there are two versions of mysqltuner.  The one I use is found
> at http://mysqltuner.pl.  I know, it's old, but it at least runs.  The
> newer one doesn't seem to have been brought to completion.
> 
> You might want to enable the slow query option that logs queries that
> execute without indexes.  They can be real killers.  Reports that use
> views often cause this as views become complex joins under the hood
> that can easily miss your indexes resulting in full table scans.
> 
> 
> --
> MySQL General Mailing List
> For list archives: http://lists.mysql.com/mysql
> To unsubscribe:http://lists.mysql.com/mysql


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Re: Slow Response -- What Does This Sound Like to You?

[Bruce Ferrell]

On 05/09/2013 03:25 PM, Robinson, Eric wrote:



-Original Message-
From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
Sent: Thursday, May 09, 2013 1:58 PM
To: mysql@lists.mysql.com
Subject: Slow Response -- What Does This Sound Like to You?

We have a situation where users complain that the system

periodically

freezes for 30-90 seconds. We check the slow query logs and

find that

one user issued a complex query that did indeed take 30-90

seconds to

complete. However, NO slow queries are recorded for the other 50
users, before, during, or after the freeze. Note that the complex
query in question always shows: "Lock_time: 0".

Q: What conditions could cause single query to lock up a

database for

a while for all users (even though it shows "lock time: 0")  but no
other slow queries would show in the logs for any other

users who are

hitting the database at the same time?

OS: RHEL3 x64
CPU: 8 x 2.9GHz Xeon
RAM: 32GB
Disk: RAID 5 (6 x 512GB SSD)
MySQL: 5.0.95 x64
Engine: MyISAM





MyISAM?  Or InnoDBm to have been finished
Lock_time perhaps applies only to table locks on MyISAM.

SHOW ENGINE InnoDB STATUS;
You may find some deadlocks.

Is Replication involved?

Anyone doing an ALTER?




MyISAM, no replication involved, and nobody is altering the database. This 
happens whenever people run certain reports.


--Eric


One thing I'd look at to start is the error log, if enabled.  After that, I'd look at running mysqltuner to get a look at statistics before and after one of these events.  I know 
there are those who prefer the Percona toolkit, but those pull lots raw stats and offers little in terms of suggestions... Unless you wish to engage Percona.


Be aware, there are two versions of mysqltuner.  The one I use is found at http://mysqltuner.pl.  I know, it's old, but it at least runs.  The newer one doesn't seem to have been 
brought to completion.


You might want to enable the slow query option that logs queries that execute without indexes.  They can be real killers.  Reports that use views often cause this as views become 
complex joins under the hood that can easily miss your indexes resulting in full table scans.



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Re: Slow Response -- What Does This Sound Like to You?

[shawn green]

Hello Eric,

On 5/9/2013 7:13 PM, Robinson, Eric wrote:

-Original Message-
From: Wm Mussatto [mailto:mussa...@csz.com]
Sent: Thursday, May 09, 2013 3:50 PM
To: Robinson, Eric
Cc: Rick James; mysql@lists.mysql.com
Subject: RE: Slow Response -- What Does This Sound Like to You?

On Thu, May 9, 2013 15:25, Robinson, Eric wrote:



-Original Message-
From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
Sent: Thursday, May 09, 2013 1:58 PM
To: mysql@lists.mysql.com
Subject: Slow Response -- What Does This Sound Like to You?

We have a situation where users complain that the system

periodically

freezes for 30-90 seconds. We check the slow query logs and

find that

one user issued a complex query that did indeed take 30-90

seconds to

complete. However, NO slow queries are recorded for the other 50
users, before, during, or after the freeze. Note that

the complex

query in question always shows: "Lock_time: 0".

Q: What conditions could cause single query to lock up a

database for

a while for all users (even though it shows "lock time:

0")  but no

other slow queries would show in the logs for any other

users who are

hitting the database at the same time?

OS: RHEL3 x64
CPU: 8 x 2.9GHz Xeon
RAM: 32GB
Disk: RAID 5 (6 x 512GB SSD)
MySQL: 5.0.95 x64
Engine: MyISAM





MyISAM?  Or InnoDB?
Lock_time perhaps applies only to table locks on MyISAM.

SHOW ENGINE InnoDB STATUS;
You may find some deadlocks.

Is Replication involved?

Anyone doing an ALTER?




MyISAM, no replication involved, and nobody is altering the

database.

This happens whenever people run certain reports.


--Eric

This may be a dumb question, but have you verified that the
applications do not issue a "Lock TABLES ..."? Either the big
one or one of the others.



I have not verified this, but it should be easy to find out. Hopefully that is 
not the case as it is a canned application and we don't have access to the code.

--Eric



Another option to keep in mind is the effect of a very large Query 
Cache. Each change to a table must invalidate every query (and their 
results) that derived from that table. For large caches, that can bring 
the server to a cold halt until the purge complete.


Try disabling it entirely and see how that affects performance or make 
it much smaller.


--
Shawn Green
MySQL Principal Technical Support Engineer
Oracle USA, Inc. - Hardware and Software, Engineered to Work Together.
Office: Blountville, TN

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RE: Slow Response -- What Does This Sound Like to You?

[Robinson, Eric]

> -Original Message-
> From: Wm Mussatto [mailto:mussa...@csz.com] 
> Sent: Thursday, May 09, 2013 3:50 PM
> To: Robinson, Eric
> Cc: Rick James; mysql@lists.mysql.com
> Subject: RE: Slow Response -- What Does This Sound Like to You?
> 
> On Thu, May 9, 2013 15:25, Robinson, Eric wrote:
> >>
> >> > -Original Message-
> >> > From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
> >> > Sent: Thursday, May 09, 2013 1:58 PM
> >> > To: mysql@lists.mysql.com
> >> > Subject: Slow Response -- What Does This Sound Like to You?
> >> >
> >> > We have a situation where users complain that the system
> >> periodically
> >> > freezes for 30-90 seconds. We check the slow query logs and
> >> find that
> >> > one user issued a complex query that did indeed take 30-90
> >> seconds to
> >> > complete. However, NO slow queries are recorded for the other 50 
> >> > users, before, during, or after the freeze. Note that 
> the complex 
> >> > query in question always shows: "Lock_time: 0".
> >> >
> >> > Q: What conditions could cause single query to lock up a
> >> database for
> >> > a while for all users (even though it shows "lock time: 
> 0")  but no 
> >> > other slow queries would show in the logs for any other
> >> users who are
> >> > hitting the database at the same time?
> >> >
> >> > OS: RHEL3 x64
> >> > CPU: 8 x 2.9GHz Xeon
> >> > RAM: 32GB
> >> > Disk: RAID 5 (6 x 512GB SSD)
> >> > MySQL: 5.0.95 x64
> >> > Engine: MyISAM
> >> >
> >
> >
> >> MyISAM?  Or InnoDB?
> >> Lock_time perhaps applies only to table locks on MyISAM.
> >>
> >> SHOW ENGINE InnoDB STATUS;
> >> You may find some deadlocks.
> >>
> >> Is Replication involved?
> >>
> >> Anyone doing an ALTER?
> >
> >
> >
> > MyISAM, no replication involved, and nobody is altering the 
> database. 
> > This happens whenever people run certain reports.
> >
> >
> > --Eric
> This may be a dumb question, but have you verified that the 
> applications do not issue a "Lock TABLES ..."? Either the big 
> one or one of the others.
> 

I have not verified this, but it should be easy to find out. Hopefully that is 
not the case as it is a canned application and we don't have access to the code.

--Eric





Disclaimer - May 9, 2013 
This email and any files transmitted with it are confidential and intended 
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named addressee you should not disseminate, distribute, copy or alter this 
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author and might not represent those of Physicians' Managed Care or Physician 
Select Management. Warning: Although Physicians' Managed Care or Physician 
Select Management has taken reasonable precautions to ensure no viruses are 
present in this email, the company cannot accept responsibility for any loss or 
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RE: Slow Response -- What Does This Sound Like to You?

[Wm Mussatto]

On Thu, May 9, 2013 15:25, Robinson, Eric wrote:
>>
>> > -Original Message-
>> > From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
>> > Sent: Thursday, May 09, 2013 1:58 PM
>> > To: mysql@lists.mysql.com
>> > Subject: Slow Response -- What Does This Sound Like to You?
>> >
>> > We have a situation where users complain that the system
>> periodically
>> > freezes for 30-90 seconds. We check the slow query logs and
>> find that
>> > one user issued a complex query that did indeed take 30-90
>> seconds to
>> > complete. However, NO slow queries are recorded for the other 50
>> > users, before, during, or after the freeze. Note that the complex
>> > query in question always shows: "Lock_time: 0".
>> >
>> > Q: What conditions could cause single query to lock up a
>> database for
>> > a while for all users (even though it shows "lock time: 0")  but no
>> > other slow queries would show in the logs for any other
>> users who are
>> > hitting the database at the same time?
>> >
>> > OS: RHEL3 x64
>> > CPU: 8 x 2.9GHz Xeon
>> > RAM: 32GB
>> > Disk: RAID 5 (6 x 512GB SSD)
>> > MySQL: 5.0.95 x64
>> > Engine: MyISAM
>> >
>
>
>> MyISAM?  Or InnoDB?
>> Lock_time perhaps applies only to table locks on MyISAM.
>>
>> SHOW ENGINE InnoDB STATUS;
>> You may find some deadlocks.
>>
>> Is Replication involved?
>>
>> Anyone doing an ALTER?
>
>
>
> MyISAM, no replication involved, and nobody is altering the database. This
> happens whenever people run certain reports.
>
>
> --Eric
This may be a dumb question, but have you verified that the applications
do not issue a "Lock TABLES ..."? Either the big one or one of the others.

--
William R. Mussatto
Systems Engineer
http://www.csz.com
909-920-9154


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Re: Slow Response -- What Does This Sound Like to You?

[Denis Jedig]

Am 09.05.2013 22:58, schrieb Robinson, Eric:


Q: What conditions could cause single query to lock up a database for a while 
for all users


From 
 
:


A SELECT statement that takes a long time to run prevents other 
sessions from updating the table in the meantime, making the 
other sessions appear slow or unresponsive. While a session is 
waiting to get exclusive access to the table for updates, other 
sessions that issue SELECT statements will queue up behind it, 
reducing concurrency even for read-only sessions.


You might try using low_priority_updates to mitigate this.

Regards,
--
Denis Jedig
syneticon networks gmbh

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Re: Slow Response -- What Does This Sound Like to You?

[Johnny Withers]

I delt with a similar situation where users complained the system would
freeze up for 30-60 seconds at random intervals. After days of looking at
queries, logs, error logs, etc.. We were no closer to finding a solution.
We do have a service that runs every 15 minutes to cache some data in our
system, in one app it creates some temporary tables. In this app the tables
were not being created as memory tables. Since we also use connection
pooling, the temporary tables created evey 15 minutes were not dropped when
the task completed. When the connection was finally closed there were a lot
of temporary tables to drop and the MySQL server would hang while this
process was completed. Changing to memory tables solved the problem.

Might not be your issue but it reminded me of this.

On Thursday, May 9, 2013, Robinson, Eric wrote:

> We have a situation where users complain that the system periodically
> freezes for 30-90 seconds. We check the slow query logs and find that one
> user issued a complex query that did indeed take 30-90 seconds to complete.
> However, NO slow queries are recorded for the other 50 users, before,
> during, or after the freeze. Note that the complex query in question always
> shows: "Lock_time: 0".
>
> Q: What conditions could cause single query to lock up a database for a
> while for all users (even though it shows "lock time: 0")  but no other
> slow queries would show in the logs for any other users who are hitting the
> database at the same time?
>
> OS: RHEL3 x64
> CPU: 8 x 2.9GHz Xeon
> RAM: 32GB
> Disk: RAID 5 (6 x 512GB SSD)
> MySQL: 5.0.95 x64
> Engine: MyISAM
>
> --
> Eric Robinson
>
>
>
>
>
>
>
> Disclaimer - May 9, 2013
> This email and any files transmitted with it are confidential and intended
> solely for mysql@lists.mysql.com . If you are not the named
> addressee you should not disseminate, distribute, copy or alter this email.
> Any views or opinions presented in this email are solely those of the
> author and might not represent those of Physicians' Managed Care or
> Physician Select Management. Warning: Although Physicians' Managed Care or
> Physician Select Management has taken reasonable precautions to ensure no
> viruses are present in this email, the company cannot accept responsibility
> for any loss or damage arising from the use of this email or attachments.
> This disclaimer was added by Policy Patrol: http://www.policypatrol.com/
>


-- 
-
Johnny Withers
601.209.4985
joh...@pixelated.net

RE: Slow Response -- What Does This Sound Like to You?

[Robinson, Eric]

> 
> > -Original Message-
> > From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
> > Sent: Thursday, May 09, 2013 1:58 PM
> > To: mysql@lists.mysql.com
> > Subject: Slow Response -- What Does This Sound Like to You?
> > 
> > We have a situation where users complain that the system 
> periodically 
> > freezes for 30-90 seconds. We check the slow query logs and 
> find that 
> > one user issued a complex query that did indeed take 30-90 
> seconds to 
> > complete. However, NO slow queries are recorded for the other 50 
> > users, before, during, or after the freeze. Note that the complex 
> > query in question always shows: "Lock_time: 0".
> > 
> > Q: What conditions could cause single query to lock up a 
> database for 
> > a while for all users (even though it shows "lock time: 0")  but no 
> > other slow queries would show in the logs for any other 
> users who are 
> > hitting the database at the same time?
> > 
> > OS: RHEL3 x64
> > CPU: 8 x 2.9GHz Xeon
> > RAM: 32GB
> > Disk: RAID 5 (6 x 512GB SSD)
> > MySQL: 5.0.95 x64
> > Engine: MyISAM
> > 


> MyISAM?  Or InnoDB?
> Lock_time perhaps applies only to table locks on MyISAM.
> 
> SHOW ENGINE InnoDB STATUS;
> You may find some deadlocks.
> 
> Is Replication involved?
> 
> Anyone doing an ALTER?



MyISAM, no replication involved, and nobody is altering the database. This 
happens whenever people run certain reports.


--Eric







Disclaimer - May 9, 2013 
This email and any files transmitted with it are confidential and intended 
solely for Rick James,mysql@lists.mysql.com. If you are not the named addressee 
you should not disseminate, distribute, copy or alter this email. Any views or 
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represent those of Physicians' Managed Care or Physician Select Management. 
Warning: Although Physicians' Managed Care or Physician Select Management has 
taken reasonable precautions to ensure no viruses are present in this email, 
the company cannot accept responsibility for any loss or damage arising from 
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RE: Slow Response -- What Does This Sound Like to You?

[Rick James]

MyISAM?  Or InnoDB?
Lock_time perhaps applies only to table locks on MyISAM.

SHOW ENGINE InnoDB STATUS;
You may find some deadlocks.

Is Replication involved?

Anyone doing an ALTER?

> -Original Message-
> From: Robinson, Eric [mailto:eric.robin...@psmnv.com]
> Sent: Thursday, May 09, 2013 1:58 PM
> To: mysql@lists.mysql.com
> Subject: Slow Response -- What Does This Sound Like to You?
> 
> We have a situation where users complain that the system periodically
> freezes for 30-90 seconds. We check the slow query logs and find that
> one user issued a complex query that did indeed take 30-90 seconds to
> complete. However, NO slow queries are recorded for the other 50 users,
> before, during, or after the freeze. Note that the complex query in
> question always shows: "Lock_time: 0".
> 
> Q: What conditions could cause single query to lock up a database for a
> while for all users (even though it shows "lock time: 0")  but no other
> slow queries would show in the logs for any other users who are hitting
> the database at the same time?
> 
> OS: RHEL3 x64
> CPU: 8 x 2.9GHz Xeon
> RAM: 32GB
> Disk: RAID 5 (6 x 512GB SSD)
> MySQL: 5.0.95 x64
> Engine: MyISAM
> 
> --
> Eric Robinson
> 
> 
> 
> 
> 
> 
> 
> Disclaimer - May 9, 2013
> This email and any files transmitted with it are confidential and
> intended solely for mysql@lists.mysql.com. If you are not the named
> addressee you should not disseminate, distribute, copy or alter this
> email. Any views or opinions presented in this email are solely those
> of the author and might not represent those of Physicians' Managed Care
> or Physician Select Management. Warning: Although Physicians' Managed
> Care or Physician Select Management has taken reasonable precautions to
> ensure no viruses are present in this email, the company cannot accept
> responsibility for any loss or damage arising from the use of this
> email or attachments.
> This disclaimer was added by Policy Patrol:
> http://www.policypatrol.com/

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