Date: Tue, 4 Nov 2003 13:52:15 +0100 (MET) From: Helge Oldach <helge.oldach@atosorigin.com> To: olli@lurza.secnetix.de (Oliver Fromme) Cc: freebsd-stable@freebsd.org Subject: Re: [4.9-RC] What happened to ``options HTT'' ? Message-ID: <200311041252.NAA03072@galaxy.hbg.de.ao-srv.com> In-Reply-To: <200311040957.hA49vGD2070104@lurza.secnetix.de> from Oliver Fromme at "Nov 4, 2003 10:57:16 am"
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Oliver Fromme: >Brooks Davis <brooks@one-eyed-alien.net> wrote: > > On Tue, Oct 28, 2003 at 11:42:57PM +0200, Jaco van Tonder wrote: > > > I just cvsup'ed to that latest -STABLE and saw that option HTT > > > is no longer availible in LINT. Does anyone know why this is no > > > longer supported? I searched the stable@ list but cant seem to > > > find anything on this. > > It is no longer necessicary as HTT logical CPUs are now > > activated by default. If you wish to use them, set the sysctl > > machdep.hlt_logical_cpus to 0. >Can that sysctl be changed at runtime, or is it only possible to do it >in the loader? The UPDATING entry isn't completely clear about that. I can confirm from experience that changing this sysctl to 0 immediately started the second logical CPU. Turning it back to 1 apparently stops processes on the second logical CPU to start, instead everything runs on CPU0. However processes running on the second CPU remain there until they terminate. >By the way, are there any "real world" experiences whether it's worth >it to use the logical CPUs, say, on a PostgreSQL or Apache server, or >with Java stuff (jakarta/tomcat etc.)? That would interest me as well. In particular I would be interested where improvements might be expected - in CPU-intensive environments, interrupt-intensive enviroments, and I/O-intensive environments. I am running a system that walks a couple of thousand files every minute - would that benefit from HTT? (I seem to recall that UFS as part of the kernel is restricted to a single CPU?) Helge
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