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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8584) Add strerror output on failed trySkipCache calls
Date Tue, 24 Mar 2015 16:04:53 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14378061#comment-14378061
] 

Benedict commented on CASSANDRA-8584:
-------------------------------------

The reason I didn't go all out is I actually think it's detrimental to optimise something
like this: it's intended to never run under normal operation; if it does run, it will almost
never be contended (we're trying to not-spam by secondly intervals, not nanosecondly); and
the logging is itself inherently blocking (as stands), and since that is hit on every log
command, not just the no-spam paths, if any contention will occur, it will likely occur there.
So, if we care at all about being non-blocking here, we should start by making our logging
non-blocking, otherwise this is just for warm fuzzy feels. I don't mind terribly, but I generally
am opposed to even minor changes that only _appear_ to deliver a benefit, since it sends potentially
erroneous signals to readers of the code that this matters here.

> Add strerror output on failed trySkipCache calls
> ------------------------------------------------
>
>                 Key: CASSANDRA-8584
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8584
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Joshua McKenzie
>            Assignee: Joshua McKenzie
>            Priority: Trivial
>             Fix For: 2.1.4
>
>         Attachments: 8584_v1.txt, NoSpamLogger.java, nospamlogger.txt
>
>
> Since trySkipCache returns an errno rather than -1 and setting errno like our other CLibrary
calls, it's thread-safe and we could print out more helpful information if we failed to prompt
the kernel to skip the page cache.  That system call should always succeed unless we have
an invalid fd as it's free to ignore us.



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