Date: Sat, 22 Dec 2007 20:03:08 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: David G Lawrence <dg@dglawrence.com> Cc: freebsd-net@freebsd.org, freebsd-stable@freebsd.org Subject: Re: Packet loss every 30.999 seconds Message-ID: <20071223040308.GT16982@elvis.mu.org> In-Reply-To: <20071222073236.GW25053@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> <20071221200810.GY16982@elvis.mu.org> <20071221234347.GS25053@tnn.dglawrence.com> <20071222002432.GK16982@elvis.mu.org> <20071222073236.GW25053@tnn.dglawrence.com>
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* David G Lawrence <dg@dglawrence.com> [071221 23:31] wrote: > > > > 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. > > > > > > That was one of the solutions that I considered and rejected since it > > > would significantly increase the overhead of the loop. > > > The solution provided by Kostik Belousov that uses uio_yield looks like > > > a find solution. I intend to try it out on some servers RSN. > > > > Out of curiosity's sake, why would it make the loop slower? one > > would only add the placeholder when yielding, not for every iteration. > > Actually, I misread your suggestion and was thinking marker flag, > rather than placeholder vnode. Sorry about that. The current code > actually already uses a marker vnode. It is hidden and obfuscated in > the MNT_VNODE_FOREACH macro, further hidden in the __mnt_vnode_first/next > functions, so it should be safe from vnode reclaimation/free problems. That level of obscuring is a bit worrysome. Yes, I did mean placeholder vnode. Even so, is it of utility or not? Or is it already being used and I'm missing something and should just "utsl" at this point? -- - Alfred Perlstein
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