Date: Tue, 23 May 2006 10:14:06 +0200 From: Lars Heidieker <lars@heidieker.de> To: m m <needacoder@gmail.com> Cc: current@freebsd.org, "Chad Leigh -- Shire.Net LLC" <chad@shire.net> Subject: Re: FreeBSD is now self-hosting on the UltraSPARC T1 Message-ID: <0B0D940E-213A-456F-964A-2D7A922D0315@heidieker.de> In-Reply-To: <1e4841eb0605221133s428d9136p3d5f7eff964167f4@mail.gmail.com> References: <1e4841eb0605211854i44c4aa4cm9dfc72506c2232ea@mail.gmail.com> <FB03D201-4154-411E-AFE4-572CEBF76A92@shire.net> <1e4841eb0605221133s428d9136p3d5f7eff964167f4@mail.gmail.com>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 22 May 2006, at 20:33, m m wrote: > On 5/22/06, Chad Leigh -- Shire.Net LLC <chad@shire.net> wrote: >> >> On May 21, 2006, at 7:54 PM, m m wrote: >> >> > While >> > on topic, the Opterons aren't SMP either, and neither are the >> > ht-Xeons... >> >> I would like t\o hear the rational for the Opterons (presumably the >> dual core ones) not being SMP. They have two independent operating >> cores in one physical package. Who cares how it is packaged? I >> would tend to agree with you on the ht-Xeon in terms of general >> descriptions. I do not know as well how the ht-xeon work as I don't >> use any but it seems to me that the "SMP" moniker, at least in >> FreeBSD, relate to how things are scheduled. > > SMP stands for "Symmetric MultiProcessing", which means that multiple > processors have equal access latency to memory - typically > accomplished by sitting the processors on a shared bus with memory. > The MultiProcessor Opterons are _NOT_ SMP, they are _NUMA_ machines, > "NonUniform Memory Access"; in the MP Opterons each processor has (or > can have) its own "local" memory, which makes up only part of the > shared address space. When an Opteron accesses an address that is not > in its "local" memory, it has to talk to a remote processor's memory, > thereby incurring a different access latency. > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current- > unsubscribe@freebsd.org" > I don't think this is right, SMP stands for "Symmetric MultiProcessing" in opposite to MultiProcessing where the OS image runs only on one CPU UMA and NUMA are a different thing, but yes a NUMA machine with big latency differences would have problems to run efficiently as a SMP machine. Therefor a dual core Opteron has SMP (two cores two caches etc) and totally UMA and a dual single core Opteron is not because it is NUMA. I don't take if this is the result. For me I would seperate NUMA/UMA from SMP and call it SMP if there are more than one processor core. Yes this leaves Intels HT in the dark I don't know if I would call that SMP, but probably I would as it appears (to the os) to be two cpus. Lars -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (Darwin) iD8DBQFEcsRTcxuYqjT7GRYRAmBwAJ9CTYwCsQlClJX+jXwl+U/rtUv0MQCgrAqo 2+MZhRW8kDdSGAvQp0mFE+c= =fDqM -----END PGP SIGNATURE-----
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