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Path: ...!eternal-september.org!feeder2.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> Newsgroups: comp.arch Subject: Re: Arm ldaxr / stxr loop question Date: Mon, 11 Nov 2024 13:53:43 -0800 Organization: A noiseless patient Spider Lines: 18 Message-ID: <vgtud7$16bjd$2@dont-email.me> References: <vfono1$14l9r$1@dont-email.me> <YROdnVIXfKmwYrn6nZ2dnZfqn_GdnZ2d@supernews.com> <vg5tf7$3tqmi$2@dont-email.me> <vgm0g1$3c2t2$3@dont-email.me> <zwwXO.842112$_o_3.379966@fx17.iad> <vgm4vj$3d2as$1@dont-email.me> <vgm5cb$3d2as$3@dont-email.me> <OnzXO.657386$1m96.281665@fx15.iad> <TfKXO.658488$1m96.146506@fx15.iad> <T99YO.79275$MoU3.7336@fx36.iad> <db6fdf85752c2b86affc911a98f1798b@www.novabbs.org> <_4oYO.862335$_o_3.103294@fx17.iad> <vgt5vc$11ikg$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Mon, 11 Nov 2024 22:53:44 +0100 (CET) Injection-Info: dont-email.me; posting-host="60c80f1a10de041ddca4d39cbf184afe"; logging-data="1257069"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX181D3RscbQdFGu5Gm08l+pYzcAvJxD/Uj4=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:mHr7TBN8ScE7G63c6xZPFg/u8K0= In-Reply-To: <vgt5vc$11ikg$1@dont-email.me> Content-Language: en-US Bytes: 2112 On 11/11/2024 6:56 AM, jseigh wrote: > On 11/11/24 08:59, Scott Lurndal wrote: > >> >> There are fully atomic instructions, the load/store exclusives are >> generally there for backward compatability with armv7; the full set >> of atomics (SWP, CAS, Atomic Arithmetic Ops, etc) arrived with >> ARMv8.1. >> > > They added the atomics for scalability allegedly. ARM never > stated what the actual issue was. I suspect they couldn't > guarantee a memory lock size small enough to eliminate > destructive interference. Like cache line size instead > of word size. For some reason it reminds me of the size of a reservation granule wrt LL/SC.