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<div class="moz-cite-prefix">On 09/11/2017 06:32 AM, Lukas Larsson
wrote:<br>
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cite="mid:CAP3zBqPJn9rMQhAkxbp3R3tWAE1U3Gqmdk6OB12amSHFGa4h9A@mail.gmail.com"
type="cite">
<div dir="ltr">Hello,
<div><br>
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<div class="gmail_extra">
<div class="gmail_quote">On Thu, Aug 31, 2017 at 10:07 AM,
Mikael Karlsson <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:karlsson.rm@gmail.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:karlsson.rm@gmail.com">karlsson.rm@gmail.com</a></a>></span>
wrote:<br>
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<div>I noticed that the secio emulator flag
(scheduler eager check for io) default value has
changed from false to true since ERTS 7.0. Could
someone explain what this means in practice, I
do not quite understand the line: "This,
however, also implies that execution of
outstanding I/O operation is not prioritized to
the same extent as when <span
class="gmail-m_-2787486722499859692gmail-code">false</span>
is passed."<br>
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<div><br>
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<div>The eager check io flag instructs the emulator when
it should check for new I/O events (internally called
check_io) in the fds that it is currently interested
in.</div>
<div><br>
</div>
<div>Without secio, the schedulers will first finish
with all work generated from the previous check_io. If
a lot of I/O events where triggered by the check_io,
ports may be temporarily prioritized higher than
processes in order to be able to do the next check_io
sooner.</div>
<div><br>
</div>
<div>With secio, the next check_io can be done before
all events of the previous check_io are consumed. When
this feature is enabled, the temporary higher
prioritization of ports is removed. This is the change
in priority that the documentation is trying to
explain.</div>
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<div> </div>
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<div>Is there any special cases where you would prefer
to still have it set to false.<br>
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<div><br>
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<div>I see no reason to not have secio enabled.<br>
</div>
<br>
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I have tested in the past to determine that secio can make Erlang
source code performance poor, if it isn't utilizing an Erlang port
type, though the testing was with Erlang/OTP 17.4
(<a class="moz-txt-link-freetext" href="https://github.com/CloudI/loadtests/raw/master/tests/http_req/loadtest/results_v1_4_0/201412_summary.pdf">https://github.com/CloudI/loadtests/raw/master/tests/http_req/loadtest/results_v1_4_0/201412_summary.pdf</a>).<br>
<br>
Best Regards,<br>
Michael<br>
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