Date: Fri, 21 Dec 2007 12:08:10 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: David G Lawrence <dg@dglawrence.com> Cc: freebsd-net@freebsd.org, freebsd-stable@freebsd.org, Bruce Evans <brde@optusnet.com.au> Subject: Re: Packet loss every 30.999 seconds Message-ID: <20071221200810.GY16982@elvis.mu.org> In-Reply-To: <20071219171331.GH25053@tnn.dglawrence.com> References: <D50B5BA8-5A80-4370-8F20-6B3A531C2E9B@eng.oar.net> <20071217102433.GQ25053@tnn.dglawrence.com> <CD187AD1-8712-418F-9F49-FA3407BA1AC7@eng.oar.net> <20071220011626.U928@besplex.bde.org> <814DB7A9-E64F-4BCA-A502-AB5A6E0297D3@eng.oar.net> <20071219171331.GH25053@tnn.dglawrence.com>
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* David G Lawrence <dg@dglawrence.com> [071219 09:12] wrote: > > >Try it with "find / -type f >/dev/null" to duplicate the problem > > >almost > > >instantly. > > > > I was able to verify last night that (cd /; tar -cpf -) > all.tar would > > trigger the problem. I'm working getting a test running with > > David's ffs_sync() workaround now, adding a few counters there should > > get this narrowed down a little more. > > Unfortunately, the version of the patch that I sent out isn't going to > help your problem. It needs to yield at the top of the loop, but vp isn't > necessarily valid after the wakeup from the msleep. That's a problem that > I'm having trouble figuring out a solution to - the solutions that come > to mind will all significantly increase the overhead of the loop. > As a very inadequate work-around, you might consider lowering > kern.maxvnodes to something like 20000 - that might be low enough to > not trigger the problem, but also be high enough to not significantly > affect system I/O performance. I apologize for not reading the code as I am swamped, but a technique that Matt Dillon used for bufs might work here. Can you use a placeholder vnode as a place to restart the scan? you might have to mark it special so that other threads/things (getnewvnode()?) don't molest it, but it can provide for a convenient restart point. -- - Alfred Perlstein
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