Date: Thu, 30 Jan 2003 11:52:10 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: John Baldwin <jhb@FreeBSD.ORG>, cvs-all@FreeBSD.ORG, cvs-committers@FreeBSD.ORG Subject: Re: RE: cvs commit: src/sys/i386/i386 mp_machdep.c Message-ID: <200301301952.h0UJqA0h089352@apollo.backplane.com> References: <XFMail.20030130114117.jhb@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
:> Log: :> MFC: Basic support for Hyperthreading. This uses the values from cpuid to :> enmuerate logical CPUs. :> :> Requested heavily by: ps : :I highly recommend turning on machdep.cpu_idle_hlt for HTT boxes as it :provides a noticable performance improvement. I'm still testing some :other patches to rework the locking code in 4.x to make use of the pause :instruction and be more intelligent about spinning on locks in general. : :-- : :John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ Ouch. That's rather counter-intuitive since idle_hlt usually degrades performance, but I see how it would improve performance on an HTT box. If the idle loop can be tightened up sufficiently - particularly if locked bus cycles can be removed from it (or removed for the HTT case anyway), then idle_hlt should go back to its more intuitive loss of performance instead of generating a performance improvement :-). Also, I perused the linux archives a bit and they had some rather severe scheduling issues with HTT. Apparently the logical cpus are not equivalent to each other (?), and are definitely not as effective as physical cpus (which makes sense), so if you have two KSEs and two physical cpus each with an extra logical cpu, you absoultely want to schedule the two KSEs on the two physical cpu's. -Matt Matthew Dillon <dillon@backplane.com> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200301301952.h0UJqA0h089352>