dlmarion opened a new issue, #3198: URL: https://github.com/apache/accumulo/issues/3198
User reported seeing [messages](https://github.com/apache/accumulo/blob/main/server/base/src/main/java/org/apache/accumulo/server/fs/FileManager.java#L268) in their logs where it was taking hours to reserve files for scan. Prior to 1.9.0 the FileManager.filePermits semaphore was fair, but was changed in [this](https://github.com/apache/accumulo/commit/86d6a69ec8e4e7fe1b187c4a53b8c0a88921ab27) commit. The commit message says, "Also in this change the file managers semaphore was switched to non-fair. The fair semaphore is expensive and can cause contention." Fair locks and semaphores have a penalty, which seems unnecessary when not running in a high contention heavy-load situation. However, when in that situation, they allow for many threads to make some progress vs a small number of threads making progress and the others doing nothing. @keith-turner - would like your thoughts on this as you were the author of the referenced commit. Was the penalty for the fair lock severe? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
