Date: Tue, 8 Feb 2011 11:00:27 GMT From: Carl <k0802647@telus.net> To: freebsd-fs@FreeBSD.org Subject: Re: kern/154228: [md] md getting stuck in wdrain state Message-ID: <201102081100.p18B0RFq096430@freefall.freebsd.org>
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The following reply was made to PR kern/154228; it has been noted by GNATS.
From: Carl <k0802647@telus.net>
To: bug-followup@FreeBSD.org, k0802647@telus.net
Cc:
Subject: Re: kern/154228: [md] md getting stuck in wdrain state
Date: Tue, 08 Feb 2011 02:59:41 -0800
For whatever reason I was not copied on the patch message, despite being
the bug reporter.
The explanation for that patch is more than a little obscure. In simpler
terms, what have you uncovered?
Does that patch implement a complete fix, partial fix, a workaround, or
what? Is it recommended I try it?
Did someone manage to reproduce my problem scenario?
Yesterday I ran into the same bug. Similar but different exercise. Again
on a remote production system. I had no choice but to try again, so I
repeated the procedure, only using a non-sparse file instead. It hung
yet again, so that should rule out sparse files as part of the problem.
I noticed in the mdconfig(8) man page this description for the "-o
[no]async" option:
'For vnode backed devices: avoid IO_SYNC for increased
performance but at the risk of deadlocking the entire
kernel.'
It seems to me the default would be "-o noasync" and that this is
supposed to avoid that particular risk for deadlock, but what command
can I use to verify whether a particular enabled memory disk is actually
using IO_SYNC or not?
Carl / K0802647
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