Date: Wed, 08 Aug 2001 08:48:13 -0600 From: "Weiguang SHI" <weiguang_shi@hotmail.com> To: grog@FreeBSD.org, tlambert2@mindspring.com Cc: bmilekic@technokratis.com, dillon@earth.backplane.com, zzhang@cs.binghamton.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: Allocate a page at interrupt time Message-ID: <F122JziWwSoRKbpG1Ki00002460@hotmail.com>
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I found an article on livelock at http://www.research.compaq.com/wrl/people/mogul/mogulpubsextern.html Just go there and search for "livelock". But I don't agree with Terry about the interrupt-thread-is-bad thing, because, if I read it correctly, the authors themself implemented their ideas in interrupt thread of the Digital Unix. Weiguang >From: Greg Lehey <grog@FreeBSD.org> >To: Terry Lambert <tlambert2@mindspring.com> >CC: Bosko Milekic <bmilekic@technokratis.com>, Matt Dillon ><dillon@earth.backplane.com>, Zhihui Zhang <zzhang@cs.binghamton.edu>, >freebsd-hackers@FreeBSD.ORG >Subject: Re: Allocate a page at interrupt time >Date: Wed, 8 Aug 2001 13:34:14 +0930 > >On Tuesday, 7 August 2001 at 1:58:21 -0700, Terry Lambert wrote: > > Bosko Milekic wrote: > >>> I keep wondering about the sagicity of running interrupts in > >>> threads... it still seems like an incredibly bad idea to me. > >>> > >>> I guess my major problem with this is that by running in > >>> threads, it's made it nearly impossibly to avoid receiver > >>> livelock situations, using any of the classical techniques > >>> (e.g. Mogul's work, etc.). > >> > >> References to published works? > > > > Just do an NCSTRL search on "receiver livelock"; you will get > > over 90 papers... > > > > http://ncstrl.mit.edu/ > > > > See also the list of participating institutions: > > > > http://ncstrl.mit.edu/Dienst/UI/2.0/ListPublishers > > > > It won't be that hard to find... Mogul has "only" published 92 > > papers. 8-) > >So much data, in fact, that you could hide anything behind it. Would >you like to be more specific? > > >>> It also has the unfortunate property of locking us into virtual > >>> wire mode, when in fact Microsoft demonstrated that wiring down > >>> interrupts to particular CPUs was good practice, in terms of > >>> assuring best performance. Specifically, running in virtual > >> > >> Can you point us at any concrete information that shows > >> this? Specifically, without being Microsoft biased (as is most > >> "data" published by Microsoft)? -- i.e. preferably third-party > >> performance testing that attributes wiring down of interrupts to > >> particular CPUs as _the_ performance advantage. > > > > FreeBSD was tested, along with Linux and NT, by Ziff Davis > > Labs, in Foster city, with the participation of Jordan > > Hubbard and Mike Smith. You can ask either of them for the > > results of the test; only the Linux and NT numbers were > > actually released. This was done to provide a non-biased > > baseline, in reaction to the Mindcraft benchmarks, where > > Linux showed so poorly. They ran quad ethernet cards, with > > quad CPUs; the NT drivers wired the cards down to seperate > > INT A/B/C/D interrupts, one per CPU. > >You carefully neglect to point out that this was the old SMP >implementation. I think this completely invalidates any point you may >have been trying to make. > > >>> wire mode means that all your CPUs get hit with the interrupt, > >>> whereas running with the interrupt bound to a particular CPU > >>> reduces the overall overhead. Even what we have today, with > >> > >> Obviously. > > > > I mention it because this is the direction FreeBSD appears > > to be moving in. Right now, Intel is shipping with seperate > > PCI busses; there is one motherboard from their serverworks > > division that has 16 seperate PCI busses -- which means that > > you can do simultaneous gigabit card DMA to and from memory, > > without running into bus contention, so long as the memory is > > logically seperate. NT can use this hardware to its full > > potential; FreeBSD as it exists, can not, and FreeBSD as it > > appears to be heading today (interrupt threads, etc.) seems > > to be in the same boat as Linux, et. al.. PCI-X will only > > make things worse (8.4 gigabit, burst rate). > >What do interrupt threads have to do with this? > >Terry, we've done a lot of thinking about performance implications >over the last 2 years, including addressing all of the points that you >appear to raise. A lot of it is in the archives. > >It's quite possible that we've missed something important that you >haven't. But if that's the case, we'd like you to state it. All I >see is you coming in, waving your hands and shouting generalities >which don't really help much. The fact that people are still >listening is very much an indication of the hope that you might come >up with something useful. But pointing to 92 papers and saying "it's >in there [somewhere]" isn't very helpful. > >Greg >-- >See complete headers for address and phone numbers > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-hackers" in the body of the message _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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