upgrade from 9.2.x to 9.3 causes significant performance degradation

Greetings,
I'm running a PostgreSQL 9.3.0 cluster (1 master with two streaming
replication hot standby slaves) on RHEL6-x86_64. Yesterday I upgraded
from 9.2.4 to 9.3.0, and since the upgrade I'm seeing a significant
performance degradation. PostgreSQL simply feels slower. Nothing
other than the version of PostgreSQL changed yesterday. I used
pg_upgrade to perform the upgrade, and ran the generated
analyze_new_cluster.sh immediately afterwards, which completed
successfully.

Prior to the upgrade, I'd generally expect a load average of less than
2.00 on the master, and less than 1.00 on each of the slaves. Since
the upgrade, the load average on the master has been in double digits
(hitting 100.00 for a few minutes), and the slaves are consistently
above 5.00.

There are a few things that are jumping out at me as behaving
differently since the upgrade. vmstat processes waiting for runtime
counts have increased dramatically. Prior to the upgrade the process
count would be consistently less than 10, however since upgrading it
hovers between 40 & 60 at all times. /proc/interrupts "Local timer
interrupts" has increased dramatically as well. It used to hover
around 6000 and is now over 20k much of the time. However, I'm
starting to suspect that they are both symptoms of the problem rather
than the cause.

At this point, I'm looking for guidance on how to debug this problem
more effectively.

thanks