Possible Threading problem with -CURRENT / MySQL?

Daryl Chance chancedj at yahoo.com
Wed Jun 16 05:12:52 GMT 2004

Sorry for the top post.

We've had this same problem (with mysqld locking up). 
I was able to get a trace, but since it's a live sql
box, I didn't have time to find your email (If I knew
I had kept a copy in my inbox, I would have done this
correctly, instead I thought I had to look up the
email in the archives) but I was able to get a ktrace
-p pid output of the process.  I let it run about 10
seconds and then killall -11 mysqld'd the process (it
allows mysqld to shutdown gracefully, thus not
corrupting our tables).

Here is the link to the .out file

here is the link to the .txt file of the kdump output

That was all I could remember to do in the short time
I had to get it back up and running :).

It's a stock kernel (w/ some minor things commented
out).  It's FBSD 5.2.1 p6

Hopefully this can help out a little.


-----Original Message-----
From: owner-freebsd-current at freebsd.org
[mailto:owner-freebsd-current at freebsd.org] On Behalf
Of Julian Elischer
Sent: Tuesday, June 15, 2004 7:21 PM
To: mike
Cc: Lasse Laursen; freebsd-current at freebsd.org;
freebsd-threads at freebsd.org
Subject: Re: Possible Threading problem with -CURRENT
/ MySQL?

On Mon, 14 Jun 2004, mike wrote:

> welcome to our hell. we've been experiencing mysql
problems on freebsd 5.x
> as well. it sounds like scheduler/threading is to
blame but we were not
> able to give sufficient or proper motivation to the
folks who could
> examine this deeper - we even offered $500 cash to
whomever stepped up to
> help resolve this.
> linux runs almost 2x as fast on the same hardware
with no configuring -
> and we get nearly the same results running in single
CPU mode vs. dual CPU
> mode on fbsd... something is definately fubar with
the mysql+fbsd5.x
> combination.
You complained about this some time ago and you have
still not responded 
with the information I suggest..

---- quote from my previous mail---------------
I'm not saying I can help particularly
but the problem is that the people who can help are
generally not
interested in databases.. what needs to happen is for 
some analysis to be made as to where the time is being
I vaguely remember you saying htat teh cpu was not
piegged when you had
this problem... You didn't indicate whether the disks
were at 100%.

to check this you should try running systat -vmstat
while noticing the slowdown and try see what is at
if it turns out that you are NOT seeing disk or CPU
then the next step would be to take a snapshot of
operations using 
ktrace -d -p (pid)  for 20 second followe by krtace -C
to turn it off

then looking at the output may give an idea of what
operations are
taking too long, and what is waiting on what..



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