Date: Wed, 12 Jan 2005 19:51:37 +0200 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: freebsd-questions@freebsd.org Subject: Re: Hyperthreading hurts 5.3? Message-ID: <20050112175137.GA2734@orion.daedalusnetworks.priv> In-Reply-To: <1869737534.20050112184102@wanadoo.fr> 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> <1869737534.20050112184102@wanadoo.fr>
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On 2005-01-12 18:41, Anthony Atkielski <atkielski.anthony@wanadoo.fr> wrote: > 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? [...] The 'separate file' is NOTES. This file is actually the complete reference of options that the kernel supports, so it's not like the SMP option is hidden or something. > 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? Because it's not always a 'profit'. The locking and synchronization overhead is not always negligible. Please, read the rest of the thread too :-) - Giorgos
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