Network Server Accelerator HTTP PerformanceWhite Paper

Network Server Accelerator HTTP Performance
Performance Data
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Conversely, if you allocate too much memory for the NSA HTTP URI cache, there may not be sufficient
memory for the file system buffer cache. This may cause file system performance to degrade, including
performance for sendfile() operations. The sendfile() routine transmits files over a network connection
directly from the file system buffer cache. Some web servers use sendfile() to service static content
requests. Insufficient memory for the file system buffer cache will degrade performance when using
sendfile() to service requests for non-cacheable static content. Therefore, a fine balance must be made
between the file system buffer cache size and the NSA HTTP URI cache size to get the best performance.
The file system buffer cache can be tuned by editing /stand/system or using the kmtune command and
modifying the following variables:
dbc_min_pct
dbc_max_pct
If the NSA HTTP maximum cache size plus the value for the minimum file system buffer cache percentage
(dbc_min_pct) is greater than 100, it is possible for all of the system memory to be used by the NSA HTTP
and file system caches. This will cause system performance to degrade.
A typical configuration is as follows:
dbc_max_pct 30
dbc_min_pct 30
NSA HTTP URI cache max percentage: 50.
Performance Data
A simulated web server environment was used to measure the performance of NSA HTTP. The workload was
a mix of static content (70%) and dynamic content (30%). The following table summarizes the results:
On workloads with only static content, the performance improvement was approximately 60 - 70%. Note that
the measurements were taken using web servers that implement copy avoidance when servicing static
requests. The performance improvements would be significantly greater when NSA HTTP is used with web
servers that do not implement copy avoidance for servicing static requests.
Number of
processors
Percent improvement (number of
simultaneous connections
117
217
413