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Date:      Tue, 3 Apr 2001 00:50:19 +0100 (BST)
From:      Andrew Gordon <arg@arg1.demon.co.uk>
To:        Greg Lehey <grog@lemis.com>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: 4.3-RC processes stuck sleeping on "inode" (?vinum) problem update
Message-ID:  <Pine.BSF.4.21.0104030015090.12196-100000@server.arg.sj.co.uk>
In-Reply-To: <20010402182909.A75576@wantadilla.lemis.com>

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On Mon, 2 Apr 2001, Greg Lehey wrote:
>                     plex->lockwaits++;                      /* waited one more time */
> -                   tsleep(lock, PRIBIO, "vrlock", 0);
> -                   lock = plex->lock;                      /* start again */
> +                   tsleep(lock, PRIBIO, "vrlock", hz);
> +                   lock = &plex->lock [-1];                /* start again */
>                     foundlocks = 0;
>                     pos = NULL;

OK, this seems to work - it's now been up 12 hours.  Observing that it had
failed during the daily level-1 dumps on each previous occasion when I had
been running 4.3-RC, I ran a level 0 dump to /dev/null by way of a stress
test.  This ran to completion (taking 5hrs12min); while running, I noticed
that there was nearly always one (sometimes two) of the dump processes
sleeping on "vrlock".  I haven't watched it this closely before to know if
this is normal, or indicates that the new hz-duration sleep is kicking in
frequently.

Unfortunately, I don't have an accurate benchmark to tell if performance
is affected; a normal level 0 dump (across the network to another machine)
takes about 7 hours, but that's limited by the performance of the gzip
process running at the other end - so 5 hours for dumping to /dev/null is
on the slow side but plausible.  Tonight's level 1 dump took 20 minutes
compared to yesterday's 10 minutes, despite producing only half the amount
of (compressed) output, but that may be a fluke.


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