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Re: random "fork: Resource temporarily unavailable"
- From: "Larry Hall (Cygwin)" <reply-to-list-only-lh at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Thu, 15 Jun 2006 23:43:26 -0400
- Subject: Re: random "fork: Resource temporarily unavailable"
- References: <4491D9B9.email@example.com>
- Reply-to: cygwin at cygwin dot com
Linda Walsh wrote:
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....
If it is NT returning failure rather than
forking, I wonder if, in order to provide a better "run-time"
If you can reproduce this problem, I would suggest trying it again with
a recent snapshot.
Larry Hall http://www.rfk.com
RFK Partners, Inc. (508) 893-9779 - RFK Office
838 Washington Street (508) 893-9889 - FAX
Holliston, MA 01746
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