Re: Syncing cpus on a multi-cpu, dual core system
- Original Message On a computational chemistry list I subscribe to there is a current thread about multi-cpu systems needing to have the cpu frequencies synced (this is in a Linux context). This is evidently not just having the cpus running at nominally the same frequency but something else in addition. A posting in the thread said variations less than 0.1% were not problematic. However, the poster said it was an issue in a dual cpu, dual core system he had set up. My questions are: 1. Is this real or an urban legend? If CPUs use the same FSB (as is the case with dual-core chip), they are already in sync. Right? For system that use multiple FSB clocks [like dual-(dualcore-CPU) systems], it might be possible to vary the clocks (as much as the manufacturer allows without hw modifications: e.g., SpeedStep, or something similar). Why someone would want to have CPUs running at precisely the same frequency is beyond my imagination. My dual core system does speedstep the two CPUs independently, it's clearly visible when running the speed monitor applets. I guess if only one thread is busy, only one CPU needs to work hard. As to why it would matter that they be in sync? My imagination runs to these two possibilities: 1) someone is writing multi-threaded software but doesn't really know how to do this correctly. 2) someone is writing ultra-high performance multi-threaded software that requires two threads on the two CPUs to be able to run in a way that doesn't risk data corruption, but needs to be able to do it without slowing down to check monitors/semaphores/other-threadsafety-devices. To address this, they've counted CPU cycles and are running a producer and consumer type scenario in such a way that the threads are perfectly out of phase with one another, so as to ensure that reads by one are not mixed in with writes by the other. I guess option 2 would be kinda legitimate, but I suspect actually a special case of 1 anyway--mainly because I find it hard to believe it has a snowball's chance in hell of working on systems that have pipelines, instruction look-ahead, etc. Might have worked on a dual 6502 based system when you knew exactly how long an instruction would take, and it always took that long :) Bottom line; I'm inclined to the urban-legend classification. $0.02 Simon __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: Syncing cpus on a multi-cpu, dual core system
- Original Message From: Stephen Montgomery-Smith [EMAIL PROTECTED] ...snip snip... The other thing I have noticed is that when I split jobs using threads so that I can use several processors, the speed up to the program is far less than one might expect - indeed sometimes it even gets slower. Stephen - This is probably Amdahl's law. Simon __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Network monitoring
I apologize that this probably isn't the most relevant list to ask this on. Suggestions for better lists will be welcome. I'm trying to monitor traffice on a 100BaseT ethernet network link. I split the line, put a hub in and am trying to run tcpdump on a box off the side of the hub. Unfortunately, it turns out the hub isn't a hub, it's a switching hub (what's not a switch about this? I don't get it). Consequently, all I see are arp packets, bootp packets, and the odd broadcast. I went to a local store to buy a hub, and guess what, they sold me another switching hub, so that has to be returned :( So, the question is, can anyone tell me the manufacturer and product name of a real (dumb) hub? I could use 10baseT instead if necessary, I just need something cheap that is a simple repeater. Of course, nobody advertizes our hub really is a totally dumb hub, not like those fancy switching hubs the competition sells ; Any suggestions? Thanks Simon __ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: req: New feature to rm? Remove file by the inode number
A couple of observations: 1) Implicit in most people's answers is the fact that a single inode can have many directory entries. That's why find is used. That's also why the solution below won't work, as it doesn't check the entire file system (nor would you want to answer y/n for all those files :) 2) The same inode number can exist for multiple files in a system. This occurs if multiple file systems exist. So, if you use find to achieve the desired effect, be very sure that you run it from the root of the target file system and that you tell it not to traverse onto other file systems. If you run it from the root directory, you're very likely to delete one or more files you didn't mean to delete. Point 2, likely as not, might explain why there's no simple mechanism for doing this from rm. At the very least you'd have to specify the file system you're referring to, and many plain users couldn't do that safely. Those that can are probably able to use find anyway. Cheers, Simon --- Raymond Wiker [EMAIL PROTECTED] wrote: Erik Udo writes: I couldn't find a way to remove files that had scandic/non-printable letters, then i remembered ls showed inode number of the file. Is it possible to remove the file by the inode number? It would be a useful feature :) I bet there is a way to remove those files, but only third party programs came to my mind. How about rm -i ./*? ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED] __ Yahoo! Mail Mobile Take Yahoo! Mail with you! Check email on your mobile phone. http://mobile.yahoo.com/learn/mail ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: system password's file
Try /etc/passwd and /etc/shadow User id and basic stuff in passwd, the encrypted passwords in shadow. I don't know if the encryption algorithms are compatible between linux and bsd or not. hth Simon --- [EMAIL PROTECTED] wrote: Hi all, I want to migrate from linux to freebsd. My linux box (mail server) have alot of user (hundreds) --this is the problem. I dont know which file which the password's file. I dont want typing user name and its password one by one. Beside of that, thereis possibly my users change their passwords. How can I do this migrating ? (save) I'm sorry my English is not good. Thanks before. regrds. ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED] You can tell whether a man is clever by his answers. You can tell whether a man is wise by his questions. Naguib Mahfouz __ Start your day with Yahoo! - Make it your home page! http://www.yahoo.com/r/hs ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to [EMAIL PROTECTED]
