Date: Wed, 12 Jan 2005 18:41:02 +0100 From: Anthony Atkielski <atkielski.anthony@wanadoo.fr> To: freebsd-questions@freebsd.org Subject: Re: Hyperthreading hurts 5.3? Message-ID: <1869737534.20050112184102@wanadoo.fr> In-Reply-To: <20050112111542.GA1651@orion.daedalusnetworks.priv> References: <9094-SnapperMsgD246FC56BE0A255B@68.243.126.247> <20050112014359.GA3722@gothmog.gr> <B8CC38DE-6455-11D9-87A5-000D93AD26C8@tntluoma.com> <35de0c30050111210235ea3060@mail.gmail.com> <20050112052901.GA61033@osiris.chen.org.nz> <167683180.20050112072014@wanadoo.fr> <20050112111542.GA1651@orion.daedalusnetworks.priv>
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Giorgos Keramidas writes: GK> You need to enable SMP too, to allow the FreeBSD kernel to use the GK> second (hyper-threaded) CPU. I found it, in a file called SMP. Why is the SMP option tucked away in a separate file? I stuck this into the config and rebuilt the kernel. Seems to run fine. I see that top has a C column now, and running a program in a continuous loop takes up exactly 50% of the machine (and two such programs take up exactly 100%), according to top. Boot messages looked a bit different: The Regents of the University of California. All rights reserved. FreeBSD 5.3-RELEASE #0: Wed Jan 12 17:55:18 CET 2005 root@freebie.atkielski.com:/usr/obj/usr/src/sys/FREEBIE-SMP Timecounter "i8254" frequency 1193182 Hz quality 0 CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2998.57-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0xf34 Stepping = 4 Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE> Hyperthreading: 2 logical CPUs real memory = 1073414144 (1023 MB) avail memory = 1045061632 (996 MB) ACPI APIC Table: <A M I OEMAPIC > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs cpu0 (BSP): APIC ID: 0 cpu1 (AP): APIC ID: 1 [...] cpu0: <ACPI CPU> on acpi0 cpu1: <ACPI CPU> on acpi0 [...] SMP: AP CPU #1 Launched! So I guess it's all working now. That was easy. I imagine this will give me a bit more horsepower for the buck, although--with only 0.2% of the machine busy under normal load even with a single processor--I guess I wasn't exactly processor-bound to begin with (I'd run out of I/O capacity long before running out of processor). But why not profit from what's there, eh? -- Anthony
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