2016-01-28 17:53 GMT+03:00 Mark Thomas <ma...@apache.org>: > On 28/01/2016 14:16, Konstantin Kolinko wrote: >> 2016-01-28 17:04 GMT+03:00 <ma...@apache.org>: >>> Author: markt >>> Date: Thu Jan 28 14:04:00 2016 >>> New Revision: 1727355 >>> >>> URL: http://svn.apache.org/viewvc?rev=1727355&view=rev >>> Log: >>> Switch OutputBuffer to a local Map of C2BConvertors. Loading testing with >>> HTTP/2 and default Tomcat home page suggests an improvement of a few >>> percent in throughput. >> >> How much memory is wasted? > > I wouldn't call that memory 'wasted'. I'd call it 'used' to gain > somewhere in the region of a 2% to 4% throughput increase. > >> Every connection (incl. keep-alive ones) will have its own map of >> encoders? Encoders are not reused across different connections? > > Using the same load test as I used for the performance numbers, I see a > retained size of less than 1MB all of which is eligible for GC. There > isn't much reuse in HTTP/2. > > If I switch to HTTP/1.1 and run the same test I end up with ~60 > instances using ~16k. Scale that up to 2000 concurrent connections and > you get ~550k so I am not worried about memory use in this case.
10000 -> 2,5 Mb. x up 100 different charsets available in JRE. The cache has to be limited to some real value. E.g. 3, 4 (ISO-8859-1, UTF-8 + one-two else). With such low count it can be a list instead of a hashmap. (Though maybe hashmap was improved in current java 8 and does not waste mush memory in this case). > I didn't measure the performance gain of this change for HTTP/1.1 but > I'd expect there to be some benefit although not as much as HTTP/2 > simply because HTTP/2 uses more concurrency for broadly the same load. > Where 2% - 4% comes from? There is a contention in SychronizedStack (a class copied from Apache Commons Collections) ? (Same charset => same compartment in ConcurrentHashMap (bad as there is no concurrently, but I think reading shall be fast there) => same SychronizedStack instance (rather bad, as it has synchronized methods)). Maybe use something else, like ConcurrentLinkedQueue ? Best regards, Konstantin Kolinko --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For additional commands, e-mail: dev-h...@tomcat.apache.org
