Debugging slowness?

Hi!

We’re using RT2.0.9 on Linux; the web server and database server are two
separate machines. We’re noticing significant slowness in a database of
< 100 tickets, usually as lag between link-click and content drawing.

I want to debug this, but I’m not certain how to go about it. Any
suggestions or pointers to FM’s I should R more closely? I’ve read the
online docs I could find …

Thanks!

–j
Jim Meyer, Geek At Large purp@wildbrain.com

Jim, have your tried tcpdump?-----Original Message-----
From: Jim Meyer [mailto:purp@wildbrain.com]
Sent: Tuesday, January 22, 2002 5:07 PM
To: Request Tracker Users Mailing List
Subject: [rt-users] Debugging slowness?

Hi!

We’re using RT2.0.9 on Linux; the web server and database server are two
separate machines. We’re noticing significant slowness in a database of
< 100 tickets, usually as lag between link-click and content drawing.

I want to debug this, but I’m not certain how to go about it. Any
suggestions or pointers to FM’s I should R more closely? I’ve read the
online docs I could find …

Thanks!

–j
Jim Meyer, Geek At Large purp@wildbrain.com

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Jim, have your tried tcpdump?

Yes, but inexpertly, I am sure. The only thing that I’m able to pin down
is that there’s a conversation going on between the two (db & web) for
that whole time. It goes something like this:

17:35:10.993291 > istanbul.43712 > odin.wildbrain.com.4140: P
472345083:47234508
6(3) ack 480442392 win 63712 <nop,nop,timestamp 146492799 104077704>
(DF)
17:35:10.993291 < odin.wildbrain.com.4140 > istanbul.43712: . 1:1(0) ack
3 win 1
6080 <nop,nop,timestamp 104096590 146492799> (DF)
17:35:10.993291 < odin.wildbrain.com.4140 > istanbul.43712: P 1:4(3) ack
3 win 1
6080 <nop,nop,timestamp 104096590 146492799> (DF)
17:35:10.993291 > istanbul.43712 > odin.wildbrain.com.4140: . 3:3(0) ack
4 win 6
3712 <nop,nop,timestamp 146492799 104096590> (DF)
17:35:11.003291 > istanbul.43712 > odin.wildbrain.com.4140: P 3:24(21)
ack 4 win
63712 <nop,nop,timestamp 146492800 104096590> (DF)

…and continues for about 5 seconds/~300 packets, after which I get
content. Unfortunately, that doesn’t tell me much. Interestingly,
though, it’s absolutely repeatable; if I hit “back” and “forward” in my
browser, the same pause happens.

I’m going to turn on debugging (tomorrow) and see if I get any time
related information to help me along.

Thanks!

–j
Jim Meyer, Geek At Large purp@wildbrain.com

check you aren’t getting any db issues.

Connect to mysql (i assume this is the database you are using)

and type “show processlist” just after you have submitted the page.

this will show what the database is doing.

Also have a look at “status”, in particular, Slow queries. this will (by
default) be the number of
queries that have taken more than 10 seconds to process (including queries
that are locked I believe).
currently our database is running at less that .1% slow queries, and people
still complain about it being
slow sometimes :slight_smile:

Make sure the database isn’t writing tables to disk as it processes the
queries… if it is, thats most likely your problem :slight_smile: you need to allocate
more memory to mysql.