[erlang-questions] trying to understand i/o threading (erl +A)

Ulf Wiger (TN/EAB) <>
Tue Nov 14 11:53:21 CET 2006


In my experience, you will gain lots with +A even when
you have a local file system, e.g. if you have applications
that to tons of disk I/O. When playing around with Mnesia,
I've encountered situations where the shell became 
unresponsive, while mnesia was busy dumping large amounts 
of data to disk. Another symptom was that CPU load went
down dramatically and the VM just seemed to be constantly 
waiting. Re-running the experiments with +A made a world
of difference.

/Ulf W

> -----Original Message-----
> From:  
> [mailto:] On Behalf Of 
> Bjorn Gustavsson
> Sent: den 14 november 2006 09:54
> To: 
> Subject: Re: [erlang-questions] trying to understand i/o 
> threading (erl +A)
> 
> Using +A option can only speed up file I/O. It is typically 
> used in embedded system where you don't have any local file 
> system, only NFS file systems.
> You are unlikely to gain anything in other configurations.
> 
> /Bjorn
> 
> "Count László de Almásy" <> writes:
> 
> > On 11/13/06, Bengt Kleberg <> wrote:
> > > in your case i would suggest measuring the performance of your
> > > application(s?) with increasing values for size, until the 
> > > performance stops increasing.
> > 
> > I was hoping for a better understanding of +A as opposed to 
> just using 
> > trial and error for every application.
> > 
> > > that might sound like hard work. as an alternative, i think i saw 
> > > somewhere that _if_ your platform uses the async thread pool you 
> > > could try setting size to one more than the number of 
> processors on 
> > > your system. in this day and age i could furthermore guess that 
> > > processors could be replaced with number of cores.
> > 
> > In other words, no one else knows the answer to my question either.
> > 
> > --
> > Cheers, László
> > 
> > _______________________________________________
> > erlang-questions mailing list
> > 
> > http://www.erlang.org/mailman/listinfo/erlang-questions
> > 
> 
> --
> Björn Gustavsson, Erlang/OTP, Ericsson AB
> 
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