[rabbitmq-discuss] Looking for guidance on R14B04 vs. R13B03 performance

Matthew Sackman matthew at rabbitmq.com
Mon Feb 20 11:28:04 GMT 2012

On Fri, Feb 17, 2012 at 11:17:24AM -0800, Matt Pietrek wrote:
> While I'm very happy with these results, I'm still puzzled. Given that all
> clients are writing to the same queue, I'd expect resource
> contention/blocking in the broker to slow things down much faster than they
> do. Any comment on this? Am I overlooking anything critical to my
> understanding?

There's a "window" of time during which no fsyncs will occur, and
txn-publishes will merely accumulate. Only when that window closes will
the fsync be performed. With a single publisher, each window can only
have a single publisher's msgs in it. But with many publishers, the
fsync is effectively amortized, and thus a higher rate is achieved - if
you monitor with strace or similar, you'll probably see the fsync rate
is not much different, regardless of the number of publishers you have
publishing to the same queue.


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