I'm trying to improve the latency of synchronous logging for Log4j: https://github.com/apache/logging-log4j2/pull/87
One of the means is "write pretouch" of the mapped file contents: https://github.com/leventov/logging-log4j2/blob/ 6d1c0e6b9a73b46ba7dd28ff853694f2012873c0/log4j-core/src/ main/java/org/apache/logging/log4j/core/appender/ UnsafeMappedByteBufferWriteTouch.java . Currently it is done as the following: when logger hits the 1st MB of the file, a task is scheduled to write-pretouch file contents between 1MB and 2MB marks (i. e. the 2nd MB) in a background thread. When logger starts to write in the 2nd MB, a task for write-pretouch of the 3rd MB is scheduled, and so on, i. e. at 1 MB blocks. Some testing is done on 4-core MBP, in 3 logging threads: - new version looks great at 2k messages/sec/thread: https://cdn.rawgit.com/leventov/eee84006a53dfb8d2acaebfe126bb499/raw/805c548d1f41e49e67b6815dde84d92be0568012/load2k.html (and pretouch actually contributes a lot to this result, without pretouch the new version is just a little better than the old) - decent at 20k: https://cdn.rawgit.com/leventov/eee84006a53dfb8d2acaebfe126bb499/raw/805c548d1f41e49e67b6815dde84d92be0568012/load20k.html - but suddenly much worse at 100k messages/sec/thread, than the old version: https://cdn.rawgit.com/leventov/eee84006a53dfb8d2acaebfe126bb499/raw/805c548d1f41e49e67b6815dde84d92be0568012/load100k.html I tried different approaches to pretouch, but it consistency incurs extremely long pauses, when running at "pretty extreme" message rates. Only not doing pretouch at all allows to avoid those pauses. Does anybody have a theory what's going on here? Is it more likely the feature of consumer-grade hardware, or the pretouch approach falls in bad inference with the MM implementation in OS X? -- You received this message because you are subscribed to the Google Groups "mechanical-sympathy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
