Ah, thanks so much for this reply Matthew. It's extremely enlightening and seems to explain what we're seeing.<br>
<br>
A follow up question just for my understanding: Are these "windows"
dynamic in nature (e.g., varying length, varying frequency, somehow tied
to current load)? Or are they more static (e.g. "Once every 20
milliseconds").<br>
<br>
Thanks again,<br>
<br>
Matt<br><br><div class="gmail_quote">On Mon, Feb 20, 2012 at 3:28 AM, Matthew Sackman <span dir="ltr"><<a href="mailto:matthew@rabbitmq.com">matthew@rabbitmq.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Fri, Feb 17, 2012 at 11:17:24AM -0800, Matt Pietrek wrote:<br>
> While I'm very happy with these results, I'm still puzzled. Given that all<br>
> clients are writing to the same queue, I'd expect resource<br>
> contention/blocking in the broker to slow things down much faster than they<br>
> do. Any comment on this? Am I overlooking anything critical to my<br>
> understanding?<br>
<br>
</div>There's a "window" of time during which no fsyncs will occur, and<br>
txn-publishes will merely accumulate. Only when that window closes will<br>
the fsync be performed. With a single publisher, each window can only<br>
have a single publisher's msgs in it. But with many publishers, the<br>
fsync is effectively amortized, and thus a higher rate is achieved - if<br>
you monitor with strace or similar, you'll probably see the fsync rate<br>
is not much different, regardless of the number of publishers you have<br>
publishing to the same queue.<br>
<span class="HOEnZb"><font color="#888888"><br>
Matthew<br>
</font></span><div class="HOEnZb"><div class="h5">_______________________________________________<br>
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