sane-project-website/old-archive/2001-07/0031.html

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<TITLE>sane-devel: Re: What's the status of sanei-thread?</TITLE>
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<H1>Re: What's the status of sanei-thread?</H1>
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<STRONG>From:</STRONG> Karl Heinz Kremer (<A HREF="mailto:khk@khk.net?Subject=Re:%20What's%20the%20status%20of%20sanei-thread?&In-Reply-To=&lt;20010702213529.A21048@khk.net&gt;"><EM>khk@khk.net</EM></A>)<BR>
<STRONG>Date:</STRONG> Mon Jul 02 2001 - 18:35:29 PDT
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On Mon, Jul 02, 2001 at 11:16:24PM +0200, Oliver Rauch wrote:
<BR>
<EM>&gt; Is there no driver based command queueing for USB?
</EM><BR>
<P>Not for the scanner driver, or at least not without modifications
<BR>
to the scanner driver.
<BR>
<P><EM>&gt; Also if there is no queueing, you can do:
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; 1) read on buffer1
</EM><BR>
<EM>&gt; 2) initiate read of buffer2
</EM><BR>
<EM>&gt; 3) sane_read can get buffer1, when buffer1
</EM><BR>
<EM>&gt; is empty wait until buffer2 is read (should already
</EM><BR>
<EM>&gt; be done) and initiate read of buffer1 again.
</EM><BR>
<EM>&gt; etc.
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; There are two problems with the reader_process
</EM><BR>
<EM>&gt; 1) fork does not work on all systems
</EM><BR>
<P>My plan actually was to make this a compile time option so that the
<BR>
original non-read-process version would still be available.
<BR>
<P><EM>&gt; 2) the pipe as IPC is not very good because the
</EM><BR>
<EM>&gt; buffer is very small (about 4KB on most systems).
</EM><BR>
<EM>&gt; This can(unnecessaryly) slow down scanning on slow
</EM><BR>
<EM>&gt; systems.
</EM><BR>
<P>Pipes are not the only IPC mechanism. Shared memory would probably be
<BR>
a lot faster. This of course may open up a totally different can of
<BR>
incompatibility worms.
<BR>
<P>Do you have any comparison data between a non-threaded and the threaded
<BR>
approach?
<BR>
<P>What was the original idea behind implementing the second process in
<BR>
some of the backends?
<BR>
<P>Karl Heinz
<BR>
<P><PRE>
--
Karl Heinz Kremer <A HREF="mailto:khk@khk.net?Subject=Re:%20What's%20the%20status%20of%20sanei-thread?&In-Reply-To=&lt;20010702213529.A21048@khk.net&gt;">khk@khk.net</A>
PGP Key at <A HREF="http://www.freecolormanagement.com/download/khk.asc">http://www.freecolormanagement.com/download/khk.asc</A>
EPSON Sane Backend: <A HREF="http://www.freecolormanagement.com">http://www.freecolormanagement.com</A>
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