Path: csiph.com!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: Anne & Lynn Wheeler Newsgroups: alt.folklore.computers,comp.sys.raspberry-pi Subject: Re: Is it a lost cause? Date: Sun, 03 Jul 2016 07:49:03 -0700 Organization: Wheeler&Wheeler Lines: 34 Message-ID: <87oa6eeq00.fsf@garlic.com> References: <20160613210220.7d9874b5@maxa-pc.cpe.bvcom.net> <440983857.489168038.520479.peter_flass-yahoo.com@news.eternal-september.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: mx02.eternal-september.org; posting-host="6a701f7a2f120c3c3ec794af16136f6c"; logging-data="11403"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18e66PzC0AKV9WmhnLknU046SnZOnU+klM=" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) Cancel-Lock: sha1:Rdjy8EirL645Mt2YQrhYKtanizw= sha1:BXk/GSngU/BW54dSJIxL2OJNJtE= Xref: csiph.com alt.folklore.computers:166404 comp.sys.raspberry-pi:12344 The Natural Philosopher writes: > MMm. well lets say you construct a CALL TABLE or JUMP TABLE > ...and modify the contents. > > or even have the power to write to the PC stack ... > > you don't need explicit machine instructions to effect self modifiable code. > > And indeed as multitasking scheduler is in a sense self modifying code. > > Effect an interruption, save the context, switch the stack pointer, > restore new context and IRET. performance issue shows up in machines that prefetch and decode a block of instructions ... where instruction modified may have already been fetched and decoded. also shows up in machines with separate I&D caches where I-cache is assumed to be read/only ... and storage modifications only show up as D-cache (I-cache issues similar to I-stream having already fetched and decode instruction before modification occurs). recent (Boyd) thread with post about having done dynamic adaptive resource management (as undergraduate in the 60s, IBM picked up and included in CP67 https://slightlyeastofnew.com/2016/06/29/bookends/ past posts on dynamic adaptive resource management (sometimes referred to as "fair share" because "fair share" was default resource policy http://manana.garlic.com/~lynn/subtopic.html#fairshare Boyd posts & URLs from around the web http://manana.garlic.com/~lynn/subboyd.html -- virtualization experience starting Jan1968, online at home since Mar1970