[logback-user] FileAppender#setBufferedIO

Lars Fischer reschifl at googlemail.com
Sun Aug 15 16:32:39 CEST 2010

Hello Holger,

2010/8/14 Holger Hoffstaette <holger.hoffstaette at googlemail.com>:
> On Fri, 13 Aug 2010 12:57:22 +0200, Lars Fischer wrote:
> >From http://logback.qos.ch/manual/appenders.html#OutputStreamAppender:
> "Given the structure of current hard drives and performance tests we have
> conducted, it appears that turning off immediate flushing or buffering of
> character to byte conversions have rather small impact on performance. As
> such, as of logback vesion 0.9.19, the ImmediateFlush, BufferedIO and
> BufferSize properties have been removed without replacement."

Sorry, I missed this part of the docu.

> I got curious and indeed it seems that the underlying file stream
> implementation does no buffering, presumably to allow for recovery.
> However by default it does not fsync on every event, so even though you
> pay the OS system call and file locking (!) overhead, the OS/drive etc.
> will likely still buffer anyway. In my experience buffering at least the
> usual 4KB (pagesize) before writing can help a lot; log event output is
> typically a lot shorter than that.
> Interestingly I remember from a few years back that *some* people with
> lots of logs on high-traffic web sites sometimes got better throughput
> from unbuffered writes (contrary to everybody's expectation), whereas
> most others said buffering was absolutely necessary and a great
> improvement.

Hmm, looks like I have to drop this feature, when switching to logback.

Thank you for the hint!


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