Date: Tue, 24 Aug 2010 19:20:07 GMT From: Garrett Cooper <gcooper@FreeBSD.org> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/145385: [cpu] Logical processor cannot be disabled for some SMT-enabled Intel procs Message-ID: <201008241920.o7OJK7hh022843@freefall.freebsd.org>
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The following reply was made to PR kern/145385; it has been noted by GNATS. From: Garrett Cooper <gcooper@FreeBSD.org> To: bug-followup@freebsd.org Cc: jkim@freebsd.org, Attilio Rao <attilio@freebsd.org>, jeff@FreeBSD.org Subject: Re: kern/145385: [cpu] Logical processor cannot be disabled for some SMT-enabled Intel procs Date: Tue, 24 Aug 2010 12:15:41 -0700 On Mon, Aug 23, 2010 at 6:33 AM, John Baldwin <jhb@freebsd.org> wrote: > On Sunday, August 22, 2010 4:17:37 am Garrett Cooper wrote: >> =A0 =A0 =A0 The following trivial patch fixes the issue on my W3520 proc= essor; AFAICS > it's what should be done after reading several of the specs because the > logical count that's tracked with ebx is exactly what is needed for > logical_cpus (it's an absolute quantity). I need to verify it with a mult= i-cpu > topology at work (the two r710s I was testing with E-series Xeons on aren= 't > available remotely right now). >> Thanks! >> -Garrett > > Jung-uk Kim and Attilio Rao have both been looking at this code recently = and > are in a better position to review the patch in the PR. (Moving jhb@ to BCC, adding jeff@ for possible input on ULE) The patch works as expected (it now properly detects the SMIT CPUs as logical CPUs), but setting machdep.hlt_logical_cpus=3D1 causes other problems with scheduling tasks because certain kernel threads get stuck at boot when netbooting (in particular I've seen problems with usbhub* and a few others bits), so in order for machdep.hlt_logical_cpus to be fixed on SMT processors, it might require some changes to the ULE scheduler to shuffle around the threads to available cores/processors? Thanks! -Garrett
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