Date: Fri, 31 Jan 2003 15:05:26 -0500 (EST) From: John Baldwin <jhb@FreeBSD.org> To: "Daniel C. Sobral" <dcs@tcoip.com.br> Cc: freebsd-current@FreeBSD.ORG, Trish Lynch <trish@bsdunix.net>, Matthew Dillon <dillon@apollo.backplane.com> Subject: Re: Hyperthreading and machdep.cpu_idle_hlt Message-ID: <XFMail.20030131150526.jhb@FreeBSD.org> In-Reply-To: <3E3AC33E.9060204@tcoip.com.br>
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On 31-Jan-2003 Daniel C. Sobral wrote: > Matthew Dillon wrote: >> :So, at the request of bmilekic, I ran netpipe on a hyperthreading box (non >> :hyperthreading, I'll do when I can turn it off in BIOS next time I'm down >> :there) >> :... >> : >> :The results are here: >> : >> :http://bsdunix.net/performance >> : >> :all information on what command line options I used is in there. >> : >> :the difference with it on is pretty substantial, might be worth noting in >> :tuning(7) >> : >> :-Trish >> : >> :-- >> :Trish Lynch trish@bsdunix.net >> >> Those results are indeed quite substantial. Before you modify >> tuning(7), though, lets wait a bit to see if anyone comes up with a >> fix to the performance issue when idle_hlt is turned off. In particular >> I would like to try using a per-cpu global test in the idle loop that >> avoids doing any locked bus cycles. >> >> Unfortunately I am not sure if I have any hyperthreading capable boxes. >> My primary machine is a pentium 4 but it is running -stable. >> >> Timecounter "i8254" frequency 1193182 Hz >> Timecounter "TSC" frequency 1296069572 Hz >> CPU: Pentium 4 (1296.07-MHz 686-class CPU) >> Origin = "GenuineIntel" Id = 0xf07 Stepping = 7 >> Features=0x3febf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,P >> AT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,<b28>,ACC> >> >> It has HTT set but it's only a 1.2GHz box and I heard somewhere that only >> 2+ GHz P4's had hyperthreading. I noticed some MFCs to stable that >> suggested hyperthreading support but I do not know if full hyperthreading >> support has been MFCd yet or is intended to be MFCd to -stable. > > AFAIK, full hyperthreading support, as it is, has been merged to > -stable. It consists of a patch to recognize the virtual CPUs, so they > will be dealt with like any SMP system, as long as HTT is enabled on the > BIOS. Well, sort of. We have no way of knowing if it is off in the BIOS unless we use the ACPI tables to enumerate CPU's (which we don't), so turning it off in the BIOS won't turn it off in FreeBSD for the time being. :) -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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