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<DIV><FONT face=Arial size=2>Not when your application starts to swap-in and out
because it is running out of RAM, and yet you still have plenty of RAM occupied
by files that have been open and read, say few months ago, and no longer needed.
Now, consider 64GB RAM of which 32 GB is occupied by cache. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Between faster and fast enough, I'm always inclined
to select fast enough, especially if that's going to allow me to use memory the
way I need to vs. the way OS forces me to.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>V.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=rapsey@gmail.com href="mailto:rapsey@gmail.com">Rapsey</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=erlang-questions@erlang.org
href="mailto:erlang-questions@erlang.org">erlang-questions@erlang.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, March 14, 2008 10:32
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [erlang-questions] Linux
O_DIRECT flag</DIV>
<DIV><BR></DIV>I don't understand. Why is that a problem? Access to RAM will
always be much faster than access to a storage array. <BR><BR><BR>
<DIV class=gmail_quote>On Fri, Mar 14, 2008 at 8:45 PM, Valentin Micic <<A
href="mailto:valentin@pixie.co.za">valentin@pixie.co.za</A>> wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid">Dear
all,<BR><BR>One thing that has to make a top 10 most-likely-to-frustrate-you
features in<BR>LINUX is its uncontrollable usage of memory for I/O caching.
Whilst good for<BR>most applications, it seems quite redundant if you
connect a big storage<BR>array that has a cache on its own.<BR>After a brief
investigation regarding ones ability to bypass the cache<BR>(performed by
our hardware supplier), I've been told that an application may<BR>bypass the
cache by porviding additional flag to "open" system call --<BR>O_DIRECT to
be more specific. I assume that file:open/2 does not support<BR>this flag,
so I'd like to ask, before we start hacking around: is there
an<BR>easy way to expose this flag, and would you consider it for inclusion
in one<BR>of the next releases. Provided that O_DIRECT does what we think it
does, of<BR>course.<BR><BR>Thanks in
advance,<BR><BR>Valenitn.<BR><BR>_______________________________________________<BR>erlang-questions
mailing list<BR><A
href="mailto:erlang-questions@erlang.org">erlang-questions@erlang.org</A><BR><A
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target=_blank>http://www.erlang.org/mailman/listinfo/erlang-questions</A><BR></BLOCKQUOTE></DIV><BR>
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