Oracle Audio Technologies A86828-01 User Manual

Page 53

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Optimizing HTTP Server Performance


This is a 20% reduction in service time. When the system is under load, the benefit
of reducing connection time with persistent connections is even greater, due to the
corresponding reduction of the TCP queue.

Reduction in Server Workload

Another benefit of persistent connections is reduction of the work load on the
server. Because the server need not repeat the work to set up the connection with a
client, it is free to perform other work. For a very inexpensive servlet (Hello World),
the CPU ms per request was reduced by approximately 10% when the same client
made 4 requests per connection. (The impact would be far less significant for a
realistic servlet application that does more work.)

httpd Process Availability

There are some serious drawbacks to using persistent connections with Apache. In
particular, because httpd processes are single threaded, one client can keep a
process tied up for a significant period of time (the amount of time depends on your


settings). If you have a large user population, and you set your


limits too high, clients could be turned away because of insufficient

httpd deamons.

The default settings for the


directives are:

KeepAlive on

MaxKeepAliveRequests 100

KeepAliveTimeOut 15

These settings allow enough requests per connection and time between requests to
reap the benefits of the persistent connections, while minimizing the drawbacks.
You should consider the size and behavior of your own user population in setting
these values on your system. For example, if you have a large user population and
the users make small infrequent requests, you may want to reduce the above
settings, or even set


to off. If you have a small population of users that

return to your site frequently, you may want to increase the settings.


There is a known problem with some browsers which will leave the server with a
TCP connection in the FIN_WAIT_2 state. If too many connections are left in this
state, the system will run out of the memory allocated for storing TCP connections,
and stop.