4. Optimize caching HTTP caching allows these resources to be saved, or cached, by a browser or proxy. Once a resource is cached, a browser or proxy can refer to the locally cached copy instead of having to download it again on subsequent visits to the web page. Thus caching is a double win: you reduce round-trip time by eliminating numerous HTTP requests for the required resources, and you substantially reduce the total payload size of the responses. Besides leading to a dramatic reduction in page load time for subsequent user visits, enabling caching can also significantly reduce the bandwidth and hosting costs for your site.
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6. Minimize round-trip times Round-trip time (RTT) is the time it takes for a client to send a request and the server to send a response over the network, not including the time required for data transfer. That is, it includes the back-and-forth time on the wire, but excludes the time to fully download the transferred bytes (and is therefore unrelated to bandwidth). For example, for a browser to initiate a first-time connection with a web server, it must incur a minimum of 3 RTTs: 1 RTT for DNS name resolution; 1 RTT for TCP connection setup; and 1 RTT for the HTTP request and first byte of the HTTP response. Many web pages require dozens of RTTs.
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8. Minimize request size Every time a client sends an HTTP request, it has to send all associated cookies that have been set for that domain and path along with it. Most users have asymmetric Internet connections: upload-to-download bandwidth ratios are commonly in the range of 1:4 to 1:20. This means that a 500-byte HTTP header request could take the equivalent time to upload as 10 KB of HTTP response data takes to download. The factor is actually even higher because HTTP request headers are sent uncompressed. In other words, for requests for small objects (say, less than 10 KB, the typical size of a compressed image), the data sent in a request header can account for the majority of the response time.
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10. Minimize payload size The amount of data sent in each server response can add significant latency to your application, especially in areas where bandwidth is constrained. In addition to the network cost of the actual bytes transmitted, there is also a penalty incurred for crossing an IP packet boundary. (The maximum packet size, or Maximum Transmission Unit (MTU), is 1500 bytes on an Ethernet network, but varies on other types of networks.) Unfortunately, since it's difficult to know which bytes will cross a packet boundary, the best practice is to simply reduce the number of packets your server transmits, and strive to keep them under 1500 bytes wherever possible.
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13. Optimize browser rendering Once resources have been downloaded to the client, the browser still needs to load, interpret, and render HTML, CSS, and Javascript code. By simply formatting your code and pages in ways that exploit the characteristics of current browsers, you can enhance performance on the client side.
29. Common Profiling Views Self Tree Telemetry CPU Duration Per Method Call Tree CPU Load Memory Size per object of type Dominator Tree Memory Load Thread Duration per thread (---) (---)
39. Last Tips & Tricks 1.) Premature Optmization is the source of all evil 2.) Validate Assumptions 3.) Avoid blind fixes as much as possible 4.) Differentiate between CPU & IO 5.) Work Together
40. Thank You Questions? [email_address] http://devworks.devcon.ph http://devcon.ph http://facebook.com/DevConPH http://twitter.com/DevConPH http://twitter.com/franz_see
Notas del editor
Eden Space: The pool from which memory is initially allocated for most objects. Survivor Space: The pool containing objects that have survived the garbage collection of the Eden space. Tenured Generation: The pool containing objects that have existed for some time in the survivor space. Permanent Generation: The pool containing all the reflective data of the virtual machine itself, such as class and method objects. With Java VMs that use class data sharing, this generation is divided into read-only and read-write areas. Code Cache: The HotSpot Java VM also includes a code cache, containing memory that is used for compilation and storage of native code. Survivor Space: The pool containing objects that have survived the garbage collection of the Eden space.
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