Date: Wed, 12 Nov 2008 21:02:50 -0800 From: David Wolfskill <david@catwhisker.org> To: Jeremy Chadwick <koitsu@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-stable@freebsd.org Subject: Re: System deadlock when using mksnap_ffs Message-ID: <20081113050250.GR69155@bunrab.catwhisker.org> In-Reply-To: <20081113044200.GA10419@icarus.home.lan> References: <20081112175826.GD26195@carrick.bishnet.net> <20081112194735.GK47073@deviant.kiev.zoral.com.ua> <20081113004102.GD24360@carrick.bishnet.net> <20081113044200.GA10419@icarus.home.lan>
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On Wed, Nov 12, 2008 at 08:42:00PM -0800, Jeremy Chadwick wrote:
> ...
> > > On Wed, Nov 12, 2008 at 05:58:26PM +0000, Tim Bishop wrote:
> > > > I've been playing around with snapshots lately but I've got a problem on
> > > > one of my servers running 7-STABLE amd64:
> > > >
> > > > FreeBSD paladin 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #8: Mon Nov 10 20:49:51 GMT 2008 tdb@paladin:/usr/obj/usr/src/sys/PALADIN amd64
> > > >
> > > > I run the mksnap_ffs command to take the snapshot and some time later
> > > > the system completely freezes up:
> > > >
> > > > paladin# cd /u2/.snap/
> > > > paladin# mksnap_ffs /u2 test.1
> > > >
> > > > It only happens on this one filesystem, though, which might be to do
> > > > with its size. It's not over the 2TB marker, but it's pretty close. It's
> > > > also backed by a hardware RAID system, although a smaller filesystem on
> > > > the same RAID has no issues.
> ...
> Then in my book, the patch didn't fix anything. :-) The system is
> still "deadlocking"; snapshot generation **should not** wedge the system
> hard like this.
>
> Also, during my own testing, I am always able to use Ctrl-T to get
> SIGINFO from the running process (mksnap_ffs). That behaviour does not
> change for me.
>
> The rest of the below information is good -- but I'm confused about
> something: is there anyone out there who can use mksnap_ffs on a
> filesystem (/usr is a good test source) and NOT experience this
> deadlocking problem?
I hadn't ever tried until I saw your message. Granted, I'm using a
smaller file system (I doubt that I have a toital of as much as 2 TB in
all my machines combined), and I'm running i386, vs. amd64. But it ran
just fine. I wasn't able to test SIGINFO; it finished before I had a
chance. (I ran it under time(1); wall clock time was 0.91 sec.)
> Literally *every* FreeBSD box I have root access
> to suffers from this problem, so I'm a little baffled why we end-users
> need to keep providing debugging output when it should be easy as pie
> for a developer to do "dump -0 -L -a -f /path/fs.dump /usr" and watch
> their system wedge.
Well, I routinely use dump/restore pipelines to copy file systems
around; never had a problem with it.
> ...
For reference:
freebeast(7.1-P)[9] uname -a
FreeBSD freebeast.catwhisker.org 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #127: Wed Nov 12 05:16:20 PST 2008 root@freebeast.catwhisker.org:/common/S3/obj/usr/src/sys/FREEBEAST i386
freebeast(7.1-P)[10] ls -la
total 4
drwxrwxr-x 2 root operator 512 Nov 12 20:53 .
drwxr-xr-x 14 root wheel 512 Jan 22 2008 ..
freebeast(7.1-P)[11] /usr/bin/time -l mksnap_ffs /S2/usr test.1
0.91 real 0.00 user 0.05 sys
976 maximum resident set size
3 average shared memory size
627 average unshared data size
109 average unshared stack size
104 page reclaims
0 page faults
0 swaps
1 block input operations
230 block output operations
0 messages sent
0 messages received
0 signals received
101 voluntary context switches
34 involuntary context switches
freebeast(7.1-P)[12] ls -la
total 1460
drwxrwxr-x 2 root operator 512 Nov 12 20:54 .
drwxr-xr-x 14 root wheel 512 Jan 22 2008 ..
-r--r----- 1 root operator 2410791056 Nov 12 20:54 test.1
freebeast(7.1-P)[13]
Peace,
david
--
David H. Wolfskill david@catwhisker.org
Depriving a girl or boy of an opportunity for education is evil.
See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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