Re: enable smp / hyperthreading
On Thu, 17 Nov 2005 23:02:39 +, dgmm wrote: From my point of view, using SMP with a single HT processor is a waste of time unless you routinely run multiple programmes which require an approximately equal amount of CPU time or you need to keep about half of your CPU time free for other programs. What about running 'make' with some -j options? Wouldnt that take advantage of the two CPUs better than if running without HT? And 'make' is used quite often ;) -- vh Jeppe W. Larsen Logic is the beginning of wisdom; not the end. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: enable smp / hyperthreading
On Monday 07 November 2005 18:53, [EMAIL PROTECTED] wrote: Hi I've just installed 6.0-RELASE and am trying to get SMP to work (I have af Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and according to dmesg the two CPUs are found: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 But I'm not sure that both are enabled, because at this is at the end of dmesg and I dont see the other CPU being enabled somewhere: SMP: AP CPU #1 Launched! According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP doesnt seem to be disabled: kern.smp.cpus: 2 kern.smp.disabled: 0 kern.smp.active: 1 So I thought that it might help to but 'kern.smp.active=2' in /boot/loader.conf, but after a reboot it is back to 1 again. What am I missing here? I'm sure people more knowledgeable than me will be able to confirm or comment further on the following but here goes anyway. From my point of view, using SMP with a single HT processor is a waste of time unless you routinely run multiple programmes which require an approximately equal amount of CPU time or you need to keep about half of your CPU time free for other programs. For example, encoding video with mplayer on a P4 with SMP enabled only used one virtual CPU. It encodes approx. twice as fast with SMP switched off (and HT switched off in BIOS) There does appear to be some lost CPU cycles due to HT switching too. Note that I've not done any serious testing or looked deeply into this subject. This is simply my limited experience. -- Dave ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: enable smp / hyperthreading
On Mon, 07 Nov 2005 11:16:19 -1000, Robert Marella wrote: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc That did the trick, I think :) -- regards, Jeppe W. Larsen Logic is the beginning of wisdom; not the end. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
enable smp / hyperthreading
Hi I've just installed 6.0-RELASE and am trying to get SMP to work (I have af Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and according to dmesg the two CPUs are found: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 But I'm not sure that both are enabled, because at this is at the end of dmesg and I dont see the other CPU being enabled somewhere: SMP: AP CPU #1 Launched! According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP doesnt seem to be disabled: kern.smp.cpus: 2 kern.smp.disabled: 0 kern.smp.active: 1 So I thought that it might help to but 'kern.smp.active=2' in /boot/loader.conf, but after a reboot it is back to 1 again. What am I missing here? regards, Jeppe Larsen ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: enable smp / hyperthreading
On Mon, Nov 07, 2005 at 07:53:20PM +0100, [EMAIL PROTECTED] wrote: Hi I've just installed 6.0-RELASE and am trying to get SMP to work (I have af Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and according to dmesg the two CPUs are found: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 But I'm not sure that both are enabled, because at this is at the end of dmesg and I dont see the other CPU being enabled somewhere: SMP: AP CPU #1 Launched! I think it is referring to the Auxiliary Processor (AP), because the BSP (don't know what that stands for, though) is obviously already active. According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP doesnt seem to be disabled: kern.smp.cpus: 2 kern.smp.disabled: 0 kern.smp.active: 1 sysctl -d kern.smp.active kern.smp.active: Number of Auxillary Processors (APs) that were successfully started This is the number of _extra_ CPUs, which chould be 1. Roland -- R.F.Smith (http://www.xs4all.nl/~rsmith/) Please send e-mail as plain text. public key: http://www.xs4all.nl/~rsmith/pubkey.txt pgpnrnQu316T8.pgp Description: PGP signature
Re: enable smp / hyperthreading
On Mon, 7 Nov 2005 20:05:24 +0100 Roland Smith [EMAIL PROTECTED] wrote: On Mon, Nov 07, 2005 at 07:53:20PM +0100, [EMAIL PROTECTED] wrote: Hi I've just installed 6.0-RELASE and am trying to get SMP to work (I have af Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and according to dmesg the two CPUs are found: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 But I'm not sure that both are enabled, because at this is at the end of dmesg and I dont see the other CPU being enabled somewhere: SMP: AP CPU #1 Launched! I think it is referring to the Auxiliary Processor (AP), because the BSP (don't know what that stands for, though) is obviously already active. According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP doesnt seem to be disabled: kern.smp.cpus: 2 kern.smp.disabled: 0 kern.smp.active: 1 sysctl -d kern.smp.active kern.smp.active: Number of Auxillary Processors (APs) that were successfully started This is the number of _extra_ CPUs, which chould be 1. Roland If hyperthreading is working the ouput of 'top' should have a C column and will show either a 0 or a 1. AFAIK HTT is still disabled because of a security risk. See: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc If you do not believe you are at risk, there is a work around included in the above site. YMMV. I have been known to be wrong before. :-) Robert ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: enable smp / hyperthreading
On Mon, 7 Nov 2005 11:16:19 -1000 Robert Marella [EMAIL PROTECTED] wrote: On Mon, 7 Nov 2005 20:05:24 +0100 Roland Smith [EMAIL PROTECTED] wrote: On Mon, Nov 07, 2005 at 07:53:20PM +0100, [EMAIL PROTECTED] wrote: Hi I've just installed 6.0-RELASE and am trying to get SMP to work (I have af Pentium 4 with HT). So I've compiled the kernel with 'options SMP' and according to dmesg the two CPUs are found: FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 But I'm not sure that both are enabled, because at this is at the end of dmesg and I dont see the other CPU being enabled somewhere: SMP: AP CPU #1 Launched! I think it is referring to the Auxiliary Processor (AP), because the BSP (don't know what that stands for, though) is obviously already active. According to 'sysctl -a' there are 2 CPUs, but only 1 active and SMP doesnt seem to be disabled: kern.smp.cpus: 2 kern.smp.disabled: 0 kern.smp.active: 1 sysctl -d kern.smp.active kern.smp.active: Number of Auxillary Processors (APs) that were successfully started This is the number of _extra_ CPUs, which chould be 1. Roland If hyperthreading is working the ouput of 'top' should have a C column and will show either a 0 or a 1. AFAIK HTT is still disabled because of a security risk. See: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc If you do not believe you are at risk, there is a work around included in the above site. YMMV. I have been known to be wrong before. :-) Robert Replying to myself. It seems that once again I am wrong. I commented out the machdep.hyperthreading_allowed=1 in /boot/loader.conf on my 6.0 system and I still have the C column and showing 2 processors. Sorry about the noise. Robert ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
