Message-ID: <4491D9B9.8010601@tlinx.org>
Date: Thu, 15 Jun 2006 15:05:45 -0700
From: Linda Walsh <cygwin AT tlinx DOT org>
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Subject: random "fork: Resource temporarily unavailable"
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I've not seen this message except when I've had to rapidly
press ^C to break out of a loop shell script.

Today, I've seen it twice when there was virtually no cpu load
on the system, about 50% virtual memory committed, and 40 processes.

Once, was with an "ls" command, the other happened as my shell was
starting up by some command invoked in the .rc script.

I get suspicious whenever I see behavior on my computers when
anomalies crop up.

I don't think any of my cygwin libraries have been updated recently.

What would cause something like this?  Memory fragmentation?
Insufficient real memory to "immediately" fork?  I.e. I wonder
if, when NT goes to "fork", if it doesn't have enough free
memory, it tells the caller it failed (try again later) and
then starts a memory cleanup cycle to free up memory: i.e. rather
than the forking process sleeping while memory is made available
NT returns it immediately with a failure.

Any idea on causes?  Is it as rare as it has been for me?
A possible solution would be retry the fork a second time, or
sleep for a millisecond and then try fork again. I'm not sure,
but I think many *ixy (*='un'|'pos'|'lin'|'ir'...etc) type programs
may not retry the fork  but immediately die, as on *ixy systems,
a fork failure is less common, and usually only happens when
the system really is out of resources.  If that's the case,
it _might_ be an aid to smooth *ixy compatibility for the
library handling fork, retry the fork (possibly with millisecond
sleep) once before returning failure to the application.

Not a high priority issue, but just wondering....

Linda
If it is NT returning failure rather than
forking, I wonder if, in order to provide a better "run-time"

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