* [9fans] hyperthreading @ 2003-12-26 23:05 andrey mirtchovski 2003-12-27 0:00 ` jmk 2003-12-27 4:10 ` [9fans] fossil/venti vdharani 0 siblings, 2 replies; 17+ messages in thread From: andrey mirtchovski @ 2003-12-26 23:05 UTC (permalink / raw) To: 9fans quick question: will Plan 9 work with hyperthreading processors? will it recognize them as dual-cpus? can you share experience with those? thanks: andrey ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-26 23:05 [9fans] hyperthreading andrey mirtchovski @ 2003-12-27 0:00 ` jmk 2003-12-27 18:39 ` jmk 2003-12-28 16:11 ` ron minnich 2003-12-27 4:10 ` [9fans] fossil/venti vdharani 1 sibling, 2 replies; 17+ messages in thread From: jmk @ 2003-12-27 0:00 UTC (permalink / raw) To: 9fans On Fri Dec 26 18:06:45 EST 2003, mirtchov@cpsc.ucalgary.ca wrote: > quick question: > > will Plan 9 work with hyperthreading processors? will it recognize them as > dual-cpus? > > can you share experience with those? > > thanks: andrey Depends. In 2002 we bought a dual-processor Xeon machine with hyperthreading. After enabling the hyperthreading option in the BIOS setup Plan 9 detects and uses 4 processors. (I don't think it makes much, if any, improvement to the system's performance). Earlier this month we tried a new single-processor P4 system with hyperthreading. Even with the BIOS option set the BIOS MP table only contains a single processor entry. I haven't bothered yet to look to see if there's some BIOS problem or if there's some other way to take advantage of hyperthreading on this system. ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-27 0:00 ` jmk @ 2003-12-27 18:39 ` jmk 2003-12-28 16:11 ` ron minnich 1 sibling, 0 replies; 17+ messages in thread From: jmk @ 2003-12-27 18:39 UTC (permalink / raw) To: 9fans I took a quick look at the P4 hyperthreading docs. It looks like we'd have to use the ACPI tables rather than the BIOS MPS table to correctly initialise the extra logical CPUs if the MPS table doesn't lie and pretend the logical CPUs are physical ones. That's more work than anyone here has time for right now. Some ACPI support would be nice in general, though. On Fri Dec 26 19:01:39 EST 2003, jmk@plan9.bell-labs.com wrote: > On Fri Dec 26 18:06:45 EST 2003, mirtchov@cpsc.ucalgary.ca wrote: > > quick question: > > > > will Plan 9 work with hyperthreading processors? will it recognize them as > > dual-cpus? > > > > can you share experience with those? > > > > thanks: andrey > > Depends. In 2002 we bought a dual-processor Xeon machine with > hyperthreading. After enabling the hyperthreading option in the > BIOS setup Plan 9 detects and uses 4 processors. (I don't think > it makes much, if any, improvement to the system's performance). > > Earlier this month we tried a new single-processor P4 system > with hyperthreading. Even with the BIOS option set the BIOS MP > table only contains a single processor entry. I haven't bothered > yet to look to see if there's some BIOS problem or if there's > some other way to take advantage of hyperthreading on this > system. ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-27 0:00 ` jmk 2003-12-27 18:39 ` jmk @ 2003-12-28 16:11 ` ron minnich 2003-12-28 22:12 ` Joel Salomon 2004-01-05 11:03 ` Vasile Rotaru 1 sibling, 2 replies; 17+ messages in thread From: ron minnich @ 2003-12-28 16:11 UTC (permalink / raw) To: 9fans hyperthreading: don't waste your time. hype-r-threading. ron ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-28 16:11 ` ron minnich @ 2003-12-28 22:12 ` Joel Salomon 2003-12-29 1:47 ` William Josephson 2003-12-31 17:08 ` ron minnich 2004-01-05 11:03 ` Vasile Rotaru 1 sibling, 2 replies; 17+ messages in thread From: Joel Salomon @ 2003-12-28 22:12 UTC (permalink / raw) To: 9fans ron minnich said: > hyperthreading: don't waste your time. > > hype-r-threading. > > ron I'm to assume then that hyperthreading is distinct from having multiple "cores" on a single die (what IBM is doing with some of their machines), or is this the "hype" you are referring to? Multiple CPUs on one silicon chip sounds cool to me. --Joel ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-28 22:12 ` Joel Salomon @ 2003-12-29 1:47 ` William Josephson 2003-12-31 17:08 ` ron minnich 1 sibling, 0 replies; 17+ messages in thread From: William Josephson @ 2003-12-29 1:47 UTC (permalink / raw) To: 9fans On Sun, Dec 28, 2003 at 05:12:32PM -0500, Joel Salomon wrote: > ron minnich said: > > hyperthreading: don't waste your time. > > > > hype-r-threading. > > I'm to assume then that hyperthreading is distinct from having multiple > "cores" on a single die (what IBM is doing with some of their machines), > or is this the "hype" you are referring to? Multiple CPUs on one silicon > chip sounds cool to me. Look up the literature on SMT (symetric multithreading). In the case of Intel, the two virtual CPUs do not have the full set of resources available to a single real CPU. The result is a modest improvement in performance for a few specific workloads and has little or negative performance impact on many others (cf. the P4 core generally -- it is a good example of microbenchmarking gone awry in my experience). I have found that with some Unix variants, typically those with underwhelming schedulers for interactive workloads, it helps a bit with keeping the shell and windowing system zippy under load. -WJ ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-28 22:12 ` Joel Salomon 2003-12-29 1:47 ` William Josephson @ 2003-12-31 17:08 ` ron minnich 1 sibling, 0 replies; 17+ messages in thread From: ron minnich @ 2003-12-31 17:08 UTC (permalink / raw) To: 9fans On Sun, 28 Dec 2003, Joel Salomon wrote: > I'm to assume then that hyperthreading is distinct from having multiple > "cores" on a single die (what IBM is doing with some of their machines), yes, it certainly is. ron ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2003-12-28 16:11 ` ron minnich 2003-12-28 22:12 ` Joel Salomon @ 2004-01-05 11:03 ` Vasile Rotaru 2004-01-05 14:31 ` David Presotto 1 sibling, 1 reply; 17+ messages in thread From: Vasile Rotaru @ 2004-01-05 11:03 UTC (permalink / raw) To: 9fans On Sun, 28 Dec 2003 17:12:48 +0100, ron minnich wrote: > hyperthreading: don't waste your time. > > hype-r-threading. > > ron Let's say if I understand it correctly. I take a very simple example, say we need to fill a big array. case a: Single processor, single thread (the base case) case b: Single processor, two threads. (one fills the even, the other the odd positions). Slower, time lost in task switch. case c: Single HP processor two threads. A litle faster than in case b), since less time lost in task switch. case d) Two processors, two threads. Solid speed gain, almost two times faster. So I just can't think of a realistic scenario, where the speed of task switching will be noticeable.. bas ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2004-01-05 11:03 ` Vasile Rotaru @ 2004-01-05 14:31 ` David Presotto 2004-01-05 15:32 ` ron minnich 0 siblings, 1 reply; 17+ messages in thread From: David Presotto @ 2004-01-05 14:31 UTC (permalink / raw) To: 9fans hyperthreading is another step down using as much of your resources as possible. With single threaded RISCs, we used instruction scheduling to try to saturate the memory bus while computing. This was pretty straightforward and just required a good compiler backend. Unfortnately, it didn't work that well. With only one thread, it was hard to always find some memory accesses to do even with speculative execution. You could switch threads but that was expensive since you had to back out much of the state of the current thread. CISCs did pretty much the same thing with multiissue machines and with Very Wide instructions. Get enough stuff to do into the machine so that at any one time the cpu elements and the memory bus were being used at the greatest efficiency. Hyperthreading is just another step down that path. If you are executing multiple threads simultaneously, there's some hope that you can find something to use the memory bus for or utilize pipeline elements for while executing the instructions. It isn't so much an attempt to reduce context switch time as it is an attempt to keep more options available to the processor's internal scheduling. Even with that, you're fighting a battle between using the chip area for a truly hyperhtreaded processor and just sticking a separate processor core on the chip. Each thread increases the amount of synchronization (and thus stalling) in the pipelines. However, each extra thread uses up less chip space than another core. The point you give up and add another processor (and syncronized write buffer) depends on the complexity of the processor itself. You're not likely to go to many threads with an x86 and have it still look like an x86. I believe someone already pointed out that there really isn't that much parallelism in the current hyperthreaded x86's. In short, hyperthreading isn't a replacement for multiprocessors. Its just a way to build a single processor with greater (in some cases) aggregate performance for the same (or not much greater) price. ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] hyperthreading 2004-01-05 14:31 ` David Presotto @ 2004-01-05 15:32 ` ron minnich 0 siblings, 0 replies; 17+ messages in thread From: ron minnich @ 2004-01-05 15:32 UTC (permalink / raw) To: 9fans hyperthreading in concept is fine. It is just that so far, on Xeon, nobody has seen a performance boost on almost any app, hence almost all the big clusters I know of have turned it off and left it off. ron ^ permalink raw reply [flat|nested] 17+ messages in thread
* [9fans] fossil/venti 2003-12-26 23:05 [9fans] hyperthreading andrey mirtchovski 2003-12-27 0:00 ` jmk @ 2003-12-27 4:10 ` vdharani 2003-12-27 4:49 ` okamoto 1 sibling, 1 reply; 17+ messages in thread From: vdharani @ 2003-12-27 4:10 UTC (permalink / raw) To: 9fans Hi, I am currently reinstalling my plan 9 machine with fossil/venti. I did a fossil based installation and also setup Venti server. At one point 'snap -a' also succeeded. When I rebooted the machine, boot process fails with the message: "boot: /386/init: not connected with venti server". I know I am clealy missing something but not sure what it is. Here are my questions: - can venti and fossil be in the same machine? - where do I specify venti server details which fossil uses? - does fossil clear the data blocks once it has saved to venti? is venti needed while booting the system? if so, who starts it? how does it get started while booting? do i need to specify in any config file? - any kernel modification is needed? - I didnt configure the network adapter yet. Is that a problem for booting? Any help appreciated. Thanks dharani ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] fossil/venti 2003-12-27 4:10 ` [9fans] fossil/venti vdharani @ 2003-12-27 4:49 ` okamoto 2003-12-27 7:52 ` vdharani 0 siblings, 1 reply; 17+ messages in thread From: okamoto @ 2003-12-27 4:49 UTC (permalink / raw) To: 9fans > fails with the message: "boot: /386/init: not connected with venti server". I'm seeing this sometime here, too. You can getout, and then, re boot fossil agian, and it'll make no harm so far. Kenji ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] fossil/venti 2003-12-27 4:49 ` okamoto @ 2003-12-27 7:52 ` vdharani 2003-12-27 5:20 ` mirtchov 2003-12-28 4:47 ` okamoto 0 siblings, 2 replies; 17+ messages in thread From: vdharani @ 2003-12-27 7:52 UTC (permalink / raw) To: 9fans hi >> fails with the message: "boot: /386/init: not connected with venti >> server". > > I'm seeing this sometime here, too. > You can getout, and then, re boot fossil agian, and it'll make > no harm so far. As I read and re-read the postings (including your posting titled 'building small Plan 9 network at home') in 9fans list, I am able to guess what is happening. Looks like fossil is not able to connect to venti probably because venti is not running, network is not up (or not configured), or fossil doesnt know the location of venti. After a couple of tries, these are the things I found (please correct me if I am wrong): - plan 9 installation is getting complex. the easiest one i did was the first free version (just a standalone system with kfs). as features are added, it getting tougher. - I tried to find out where installation script stores 'flproto' file but I couldnt. I also couldnt find out where Venti's address is stored that fossil can use. - i think kfs file system is needed anyway atleast till fossil kernel is built and the config files are modified accordingly. it is not possible or easy to setup fossil/venti without kfs. am i right? - looks like if the IP address or network changes, fossil may hesitate to start. So having 'localhost' configuration for fossil/venti communication may be useful. - The Wiki document titled 'Setting Up Fossil' is useful but if I am right, it was written for a fresh fossil installation (instead of installation-process-assisted fossil installation). So I am not sure what is done already and what needs to be done. In particular, I am struggling to get read-write permission on any file (like disk/kfscmd allow). I will be happy if someone can give your suggestions. Any help appreciated. I used to feel I am just a end-user to Plan 9. This attempt made me even more worried. :-( regards dharani ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] fossil/venti 2003-12-27 7:52 ` vdharani @ 2003-12-27 5:20 ` mirtchov 2003-12-28 4:47 ` okamoto 1 sibling, 0 replies; 17+ messages in thread From: mirtchov @ 2003-12-27 5:20 UTC (permalink / raw) To: 9fans > I will be happy if someone can give your suggestions. Any help appreciated. remove 'venti=' from plan9.ini and see if it boots ok. if the venti resides on the same disk as the fossil (or the same system that is currently booting) then set the venti to point to a disk directly, instead of using an IP address. here's what my machine uses: venti='#S/sdC0/arenas' as for fossil+venti being more complex than kfs -- venti gives you more than anything kfs ever did, so it is expected that its configuration is more complex since it's so site-specific. if, instead, you had skipped the venti config and just did a standalone fossil install you'ld find it just as easy as kfs... andrey ps: best thing to do once you get it working is to tear it down and rebuild it again :) ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] fossil/venti 2003-12-27 7:52 ` vdharani 2003-12-27 5:20 ` mirtchov @ 2003-12-28 4:47 ` okamoto 2003-12-28 8:22 ` vdharani 1 sibling, 1 reply; 17+ messages in thread From: okamoto @ 2003-12-28 4:47 UTC (permalink / raw) To: 9fans > - plan 9 installation is getting complex. the easiest one i did was the > first free version (just a standalone system with kfs). as features are > added, it getting tougher. I agree, and that is the reason why I posted my example for someone who will have the same problem, too. Complicated, because we have three kinds of file servers, and the last one, which is expected to active now, is still in the progress. If you just want to try Plan 9, you can choose kfs version, because it's easier. > - i think kfs file system is needed anyway atleast till fossil kernel is > built and the config files are modified accordingly. it is not possible or > easy to setup fossil/venti without kfs. am i right? If you don't have working Plan 9 network, I think you need kfs system first, from which you can fill the things into venti archive disk.☺ > (instead of > installation-process-assisted fossil installation). I don't know this. Is there? > I used to feel I am just a end-user to Plan 9. Looks like so.☺ Kenji ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] fossil/venti 2003-12-28 4:47 ` okamoto @ 2003-12-28 8:22 ` vdharani 2003-12-28 6:40 ` andrey mirtchovski 0 siblings, 1 reply; 17+ messages in thread From: vdharani @ 2003-12-28 8:22 UTC (permalink / raw) To: 9fans >> - plan 9 installation is getting complex. the easiest one i did was >> the first free version (just a standalone system with kfs). as >> features are added, it getting tougher. > > I agree, and that is the reason why I posted my example for someone who > will have the same problem, too. yeah, i found the note you have posted only after sending my request. > Complicated, because we have three kinds of file servers, and the last > one, which is expected to active now, is still in the progress. If > you just want to try Plan 9, you can choose kfs version, because it's > easier. No, no. I have been using kfs (and venti) for a long time. I wanted to try fossil with venti now. >> - i think kfs file system is needed anyway atleast till fossil kernel >> is built and the config files are modified accordingly. it is not >> possible or easy to setup fossil/venti without kfs. am i right? > If you don't have working Plan 9 network, I think you need kfs system > first, from which you can fill the things into venti archive disk.⺠ah, now i get it. i was wondering how you have all tried fossil and started discussing about it. i didnt know you have to use kfs initially or some working plan 9 machine before fossil is in place. this is what i tried to do: the boot floppy asked whether i want kfs or fossil. i chose fossil. I was thinking, instead of kfs, I can use fossil (with venti). looks like fossil/venti can be up and running only after necessary steps are taken. >> (instead of >> installation-process-assisted fossil installation). > > I don't know this. Is there? yes. ^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [9fans] fossil/venti 2003-12-28 8:22 ` vdharani @ 2003-12-28 6:40 ` andrey mirtchovski 0 siblings, 0 replies; 17+ messages in thread From: andrey mirtchovski @ 2003-12-28 6:40 UTC (permalink / raw) To: 9fans Here is the most straightforward way to get a fossil+venti system on a single machine (not necessarily single disk): - install from cd/net, leaving a reasonable amount of space for venti (the exact sizes are discussed in the wiki) - boot the brand new fossil system and configure the venti partitions as explained in 'Configuring Venti' on the wiki - write the venti configuration to an arena partition (venti/conf) - set venti= in plan9 .ini to point to the partition containing the venti configuration - reboot, connect to the fossil console and do a 'snap -a', then configure other parameters such as snaptimes. it's a good idea to store the fossil and venti configurations offsite, just in case As with most other Plan 9 things, the learning curve is very steep at the beginning but, as many have found out, once realized, the system presents very few surprises. Having worked with venti and a crashy fossil for a while I've come to realize that much more attention needs to be paid to venti since fossil servers could be discarded freely, as long as the data in venti is intact. andrey ^ permalink raw reply [flat|nested] 17+ messages in thread
end of thread, other threads:[~2004-01-05 15:32 UTC | newest] Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2003-12-26 23:05 [9fans] hyperthreading andrey mirtchovski 2003-12-27 0:00 ` jmk 2003-12-27 18:39 ` jmk 2003-12-28 16:11 ` ron minnich 2003-12-28 22:12 ` Joel Salomon 2003-12-29 1:47 ` William Josephson 2003-12-31 17:08 ` ron minnich 2004-01-05 11:03 ` Vasile Rotaru 2004-01-05 14:31 ` David Presotto 2004-01-05 15:32 ` ron minnich 2003-12-27 4:10 ` [9fans] fossil/venti vdharani 2003-12-27 4:49 ` okamoto 2003-12-27 7:52 ` vdharani 2003-12-27 5:20 ` mirtchov 2003-12-28 4:47 ` okamoto 2003-12-28 8:22 ` vdharani 2003-12-28 6:40 ` andrey mirtchovski
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