On Tue, Apr 18, 2017 at 02:03:19PM -0400, Chris Gamache wrote: > I had any frame of reference to base a decision on, I wouldn't have asked > the question. Ask any front-end engineer what the single best thing to do > to make a user's experience better when accessing a single-page web > application, they will say "enable compression" so why it isn't turned on > by default was a mystery, and that it plays second fiddle to serving static > file from the file system in an efficient manner was a double mystery. > > Perhaps if my fellow tomcat users would share their thought processes in > their particular situations for selecting one method over the other, that > might help me look at my own situation and make a good decision.
Well, why does one want to use sendfile()? Why does one want to use compression? sendfile() can be more efficient on the server end, by reducing the number of context switches when sending large files: one switch into kernel mode is all that is needed to get the file sent. So if you have a lot of concurrent users and fairly large files, this economy might dominate the user experience. OTOH compression can make more efficient use of lower-bandwidth links, because it sends fewer bits in fewer packets to accomplish the same task. So if you have a lot of users on slow links then this economy might dominate the user experience. Note that compression uses more CPU at both ends, so a server already running flat-out or a large community of low-powered clients may eat up any savings, and then some. How to know which is most important? Measure! The simplest approach would be to try it each way and ask users how they experienced the result. If you have a lot of information about the distribution of bandwidth and CPU power across your user community, the amount of data to be sent per request, and the shape of traffic over time, you can make some shrewd guesses, but in the end the best solution is the one that does the job best, and the only way to know that is to test and see. -- Mark H. Wood Lead Technology Analyst University Library Indiana University - Purdue University Indianapolis 755 W. Michigan Street Indianapolis, IN 46202 317-274-0749 www.ulib.iupui.edu
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