Date: Wed, 12 Nov 2008 21:00:53 -0800 (PST) From: Doug Ambrisko <ambrisko@ambrisko.com> To: Jeremy Chadwick <koitsu@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, Tim Bishop <tim@bishnet.net>, freebsd-stable@freebsd.org Subject: Re: System deadlock when using mksnap_ffs Message-ID: <200811130500.mAD50rqt051930@ambrisko.com> In-Reply-To: <20081113044200.GA10419@icarus.home.lan>
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Jeremy Chadwick writes:
[snip]
| 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? 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.
We can at work, but we have a bunch of other patches. There are a
few problems with the buffer cache:
1) The buffer daemon can't use the space that is reserved for it
since to flush some stuff it needs to use more buffers.
2) The buffer cache can get fragmented to prevent large I/O
which the buffer daemon may need.
3) Other issues ...
I have fix for "1". It is pretty easy. I have a hack'ish fix for "2"
in the I make all request use max size so it can't get fragmented
since there is no code to defrag and it isn't trivial to defrag the
memory. I have some fixes for some other issues, but there were
some review issues with them. I might just commit the fixes for 1 and
2. It makes things better and there was no-objections at the time.
We have the patches in shipping products.
I can try to do some experiments at work like you said since I
had similar things working before and it is pretty easy to put in
printf's to see the issue.
Doug A.
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