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From:Michael Widenius Date:October 16 1999 12:35pm
Subject:RE: Strange lock up (repost)
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>>>>> "Timothy" == Timothy Chi <tchi@stripped> writes:

Timothy> Hi Sinisia,
>> Please check a size of your partition where database files are.
Timothy> 17 Gig, about 9% used


>> Second, do you use any table locks ??
Timothy> No, we don't use any table locks.

Timothy> Interestingly enough, we've been on the phone with Sun and they gave us a
Timothy> few commands to run to track the processor utilization.  The mpstat command
Timothy> gave us an abnormally high value for the "smtx" column (which basically
Timothy> represents cross-processor locking).  Sun said that this number, at its
Timothy> highest should be around 200, and our system is reporting values up towards
Timothy> 13,000.  Sun said that most of the threads are user threads causing this, so
Timothy> that this is an application related issue.

Timothy> Here's the snip from Sun Tech Support:

>> The data you sent appears to verify that there is a lock contention
>> issue caused by MySQL itself.  This article describes how to 
>> interpret the
>> data, and how to collect more data about the application itself:
>> http://www.sunworld.com/swol-08-1998/swol-08-perf.html I'll leave 
>> this open until you've looked at that, and checked the resources for 
>> MySQL.

Hi!

This could be bug similar to the one we resently found in the FreeBSD
mutex implemention.

You can test this by removing from handler.cc all rows that includes:

pthread_mutex_lock(&LOCK_status);
pthread_mutex_unlock(&LOCK_status);

(MySQL 3.23.5 will include much better version of the above fix, but
the above should be ok for you).

Any change you can send us the output from '/usr/proc/bin/pstack' on
the mysqld process and 'mysqladmin proc' when you get problems.

In the worst case, this could be a problem with the key cache mutex.
You can test this by running without any key cache!

mysqld -O key_buffer=0

Does any of the above suggestions help ?


Regards,
Monty

Thread
RE: Strange lock up (repost)Timothy Chi5 Oct
  • RE: Strange lock up (repost)Michael Widenius7 Oct
RE: Strange lock up (repost)Timothy Chi5 Oct
  • RE: Strange lock up (repost)Michael Widenius7 Oct
  • RE: Strange lock up (repost)Michael Widenius16 Oct
RE: Strange lock up (repost)sinisa5 Oct
  • RE: Strange lock up (repost)Roy Teahen15 Oct