Performance Misconfiguration

There are a number of performance challenges that many websites find themselves, but nothing worse than the Misconfiguration. Last week, a customer noted that “my site seems very slow.” So I fired up Gomez and started testing. The page was very heavy at over 1.5 Mbytes, but still, 70 seconds on average was terrible! I drilled into the data on behalf of the customer and saw swings of excessively long Content Download times, which usually indicates something is misconfigured with the web server. Note the graph showing the oscillation up and down. Not only are things slow, but swinging wildly, totally inconsistent.

So how did things get fixed?

The engineers looked at the switch ports and found this:

#sho int g2/370

GigabitEthernet2/370 is up, line protocol is up (connected)

Hardware is C6k 1000Mb 802.3, address is 001f.ca6f.8424 (bia 001f.ca6f.8424)

Description: serverwww:eth0

MTU 1500 bytes, BW 100000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 10/100/1000BaseT

input flow-control is off, output flow-control is off

Clock mode is auto

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 40w2d, output hang never

Last clearing of “show interface” counters 00:21:11

Input queue: 0/2000/389/0 (size/max/drops/flushes);

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

4114 packets input, 4232945 bytes, 0 no buffer

Received 21 broadcasts (0 multicasts)

2 runts, 0 giants, 0 throttles

389 input errors, 108 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

4400 packets output, 1192528 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

So basically, the silly ports on the switch and the server were in a mismatch. Packets were getting dropped or munged between the switch and the server. After manually checking both sides and making sure everything was set, the performance impact was HUGE! Think of over 55 seconds on average. WOW!

So … checking all the silly details gives us huge wins for the customer. Another misconfiguration win!