Date: Sat, 18 Sep 2010 08:50:07 GMT From: Andriy Gapon <avg@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: <201009180850.o8I8o70H020473@freefall.freebsd.org>
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The following reply was made to PR kern/145385; it has been noted by GNATS.
From: Andriy Gapon <avg@freebsd.org>
To: bug-followup@freebsd.org, gcooper@freebsd.org,
Jeff Roberson <jroberson@jroberson.net>
Cc:
Subject: Re: kern/145385: [cpu] Logical processor cannot be disabled for some
SMT-enabled Intel procs
Date: Sat, 18 Sep 2010 11:48:39 +0300
Regarding the part of the patch that sets logical_cpus - I don't really
understand what logical_cpus represents.
It seems that in topo_probe_0x4() it's set to maximum (possible) number of
logical CPUs per whole package (for BSP package). In topo_probe_0xb(), as
you've spotted, it was not set at all.
We already have cpu_logical variable (talk about confusing names) and that
represents number of logical CPUs per core.
So, I think that logical_cpus should be abolished altogether and cpu_logical
should be used in its place.
That would be the end of topo_probe_0x4() where hyperthreading_cpus is assigned
with fallback value and init_secondary() where it's used to set logical_cpus_mask.
P.S. The code also doesn't seem to properly handle a case where
boot_cpu_id % logical_cpus != 0
and/or
boot_cpu_id % hyperthreading_cpus !=0
Not sure if that ever happens in real systems, though.
--
Andriy Gapon
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