[erlang-questions] Low disk logging performance in SMP

Ahmed Ali <>
Sun Apr 26 09:21:36 CEST 2009


Hi,

I guess this is similar to the findings in the blogs below. I didn't
know selective receives are so slow but apparently you are right, sync
processing is much better for these kind of situations. I always
thought this is due to bad IO performance.

http://blogtrader.net/dcaoyuan/entry/a_case_study_of_scalable
http://blogtrader.net/dcaoyuan/entry/async_or_sync_log_in

Having said that, I'm curious of a solution to the selective receive
slowness in erlang. Does any one think a solution like appending
messages to BDB-style persistent queues or memcacheq helps? This is
particularly useful in cases where high load could lead to large
queues and possibly a crash. I've seen such a solution in a telecom
application which is working quite fine.

http://log4erl.blogspot.com/2009/04/log4erl-issue-when-high-load.html

Best regards,

Ahmed

On Sat, Apr 25, 2009 at 1:05 AM, Per Melin <> wrote:
> Hynek Vychodil:
>> I have no problem with mine version, it does about 5MB/s for me.
>
> I would expect your version to be fast, because you empty the message
> queue before you write to disk and thus avoids any problems caused by
> selective recieves in the file modules.
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