Date: Thu, 12 Apr 2007 10:54:17 +0200 From: des@des.no (Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?=) To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: freebsd-fs@FreeBSD.ORG, freebsd-current@FreeBSD.ORG, Pawel Jakub Dawidek <pjd@FreeBSD.ORG>, ticso@cicely.de Subject: Re: ZFS committed to the FreeBSD base. Message-ID: <86ps6aht1i.fsf@dwp.des.no> In-Reply-To: <20070412073605.GB834@turion.vk2pj.dyndns.org> (Peter Jeremy's message of "Thu, 12 Apr 2007 17:36:06 %2B1000") References: <20070406025700.GB98545@garage.freebsd.pl> <86k5wo55s0.fsf@dwp.des.no> <20070407203411.GJ8831@cicely12.cicely.de> <86wt0n3mxv.fsf@dwp.des.no> <20070411214911.GA38351@VARK.MIT.EDU> <20070412073605.GB834@turion.vk2pj.dyndns.org>
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Peter Jeremy <peterjeremy@optushome.com.au> writes: > There's a feature bit (CPUID_CX8) that advertises the availability of > cmpxchg8b (and maybe some related instructions). My pre-MMX 586 has > this bit set so I presume anything later than 486 will support it. > (I'm not sure about the low-end VIA, GEODE etc clones). The Geode is a 486, and does not support it. The C3 however is a 586. The C3 Ezra and C3 Samuel / Samuel 2 do not have CX8. I'm not sure about the C3 Nehemiah, I don't have one running at the moment. > I agree that GENERIC should run on lowest-common-denominator hardware > (the definition of that is a subject for a different thread). GENERIC > performance could be enhanced by using an indirect call for 8-byte > atomic instructions and selecting between the cmpxchg8b and > alternative implementation as part of the CPU startup (much like > i586_bcopy). If CPU_486 is not defined, you code could inline the > cmpxchg8b-based variant. Our native atomic operations are all defined as either macros or static inline functions in machine/atomic.h, so we can easily make this choice at compile time based on a config option. DES --=20 Dag-Erling Sm=F8rgrav - des@des.no
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