Re: Ancient, unsolved high-CPU problem

[Doug Bridgens]

it's all a bit too general, we could be asking continual questions  
until someone asks the right one.

However, I would put some debugging into the 30% scripts to check they  
complete before the next one starts, as if one script takes slightly  
longer (especially if the queries are the same) to complete then the  
rest build up quickly.   Something else could be locking the table  
that your cron queries are trying to access, causing the stacking that  
never recovers.

Once the problem occurs I'd be using 'show processlist' in mysql, and  
vmstat and ps to check the system resources.   Is it definitely mysql,  
or php/apache, a slow disk, etc..

In terms of your stats below, I  have (on a fairly average spec  
server) 500 queries per second and 2000 open tables.   So, unless it's  
a PC or very badly tuned, it should be fine.

cheers,
Doug


On 23 Sep 2008, at 14:16, Rene Fournier wrote:

> 10% of queries are web-based (Apache/PHP).
> 30% of queries are from command-line PHP scripts that get executed  
> (average 1/second -- they end with mysql_close() btw).
> 60% of queries are from command-line PHP scripts that run  
> continuously (in a loop, with sleep()), acting on incoming socket  
> data.
>
> ...Rene
>
> On 23-Sep-08, at 2:20 PM, Jeffrey Santos wrote:
>
>> Rene,
>>
>> How are you querying the database during normal use?  What kind of  
>> applications are you using?
>>
>> ~Jeffrey Santos
>>
>> On Mon, Sep 22, 2008 at 2:46 PM, Rene Fournier  
>> <m5@stripped> wrote:
>> Uptime: 1054977  Threads: 10  Questions: 15576766  Slow queries:  
>> 229  Opens: 489  Flush tables: 1  Open tables: 483  Queries per  
>> second avg: 14.765
>>
>> ----
>>
>> I know what the slow queries are--some that take 20-30 seconds to  
>> compute, and they are normal. The number of open tables seems high,  
>> no? The database that gets 95% of the load has ~35 tables in total.
>>
>> As for cron jobs, I have a number of command-line PHP scripts that  
>> perform regular queries. They've been running for about 10 days  
>> now. The current high CPU state started a couple days ago.
>>
>>
>>
>>
>> On 22-Sep-08, at 8:30 PM, Martin Gainty wrote:
>>
>> curious if you have any cron jobs starting to execute?
>>
>> what does mysqladmin status show ?
>>
>> Martin
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>> > From: m5@stripped
>> > To: mysql@stripped
>> > Subject: Ancient, unsolved high-CPU problem
>> > Date: Mon, 22 Sep 2008 19:41:25 +0200
>>
>> >
>> > For the longest time, I've had a strange problem with MySQL.
>> > Basically, after a certain amount of time--sometimes a few days,
>> > sometimes a couple weeks--its CPU usage will go from a steady  
>> 20-30%
>> > to 80-90%. Actual load and number of queries is the same, nothing  
>> else
>> > changes.
>> >
>> > If I shutdown MySQL and restart it (not the server), CPU% goes  
>> back to
>> > normal. What could this be?
>> >
>> > (Xserve G5 2GHz, 8GB, 3x250GB RAID5, Mac OS X 10.4.11, MySQL  
>> 5.0.51a)
>> >
>> > ...Rene
>> >
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