Date: Sun, 30 Jul 2006 21:54:27 +1000 From: Peter Jeremy <peterjeremy@optushome.com.au> To: Michal Mertl <mime@traveller.cz> Cc: Paul Allen <nospam@ugcs.caltech.edu>, freebsd-current@freebsd.org Subject: Re: vmstat's entries type Message-ID: <20060730115427.GD1310@turion.vk2pj.dyndns.org> In-Reply-To: <1154250451.23616.37.camel@genius.i.cz> References: <20060728210154.GC748@turion.vk2pj.dyndns.org> <1154189612.1565.10.camel@genius.i.cz> <20060729205655.GE748@turion.vk2pj.dyndns.org> <20060729211530.GA50342@uk.tiscali.com> <1154212340.3609.18.camel@genius.i.cz> <20060729230214.GI12597@groat.ugcs.caltech.edu> <1154216319.23616.23.camel@genius.i.cz> <1154217036.23616.28.camel@genius.i.cz> <20060730005342.GJ12597@groat.ugcs.caltech.edu> <1154250451.23616.37.camel@genius.i.cz>
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--iVCmgExH7+hIHJ1A Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, 2006-Jul-30 11:07:31 +0200, Michal Mertl wrote: >Paul Allen wrote: >> Which FreeBSD tier-I 64b arch do you have in mind... > >I was referring to what Peter Jeremy said earlier in this thread: > >> RISC architectures usually only have TAS lock primitives (because "inc >> mem" doesn't exist) and so require a spinlock to perform an atomic >> update. This was based on an examination of /usr/src/sys/*/include/atomic.h. It looks like I was overly quick because the RISC architectures are using compare-and-swap, rather than test-and-set primitives - sorry about the error. The details are: - Alpha (RIP) used a loop around a locked conditional store - amd64 appears to support RMW - arm doesn't support 64-bit atomic operations - i386 doesn't support 64-bit atomic operations (but could implement them using cmpxchg8b in a loop) - ia64 uses cmpxchg in a loop - ppc doesn't support 64-bit atomic operations - sparc64 uses cas in a loop. Whilst true spinlocks are not needed, amd64 is the only architecture FreeBSD supports that does not require some sort of loop to perform a 64-bit atomic operation. --=20 Peter Jeremy --iVCmgExH7+hIHJ1A Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (FreeBSD) iD8DBQFEzJ3z/opHv/APuIcRAvVoAJwJlui519oOiZLyP8+5iFYaitQ10wCePe84 eyYj5Yh1vv42M52G46YwlBg= =mU7A -----END PGP SIGNATURE----- --iVCmgExH7+hIHJ1A--
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