Messages in this thread | | | Date | Mon, 14 Apr 2003 22:49:03 -0700 | From | "Martin J. Bligh" <> | Subject | Re: cow-ahead N pages for fault clustering |
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>> > >> Ah, you probably don't want to do that ... it's very expensive. >> > >> Moreover, if you exec 2ns later, all the effort will be wasted ... >> > >> and it's very hard to deterministically predict whether you'll exec >> > >> or not (stupid UNIX semantics). Doing it lazily is probably best, >> > >> and as to "nodes would not have to reference the memory from >> > >> others" - you're still doing that, you're just batching it on the >> > >> front end. >> > > >> > > True... What about a vma-level COW-ahead just like we have a >> > > file-level read-ahead, then? I mean batching the COW at >> > > unCOW-because-of-write time. >> > >> > That'd be interesting ... and you can test that on a UP box, is not >> > just NUMA. Depends on the workload quite heavily, I suspect. >> > >> > > btw, COW-ahead sound really silly :) >> > >> > Yeah. So be sure to call it that if it works out ... we need more >> > things like that ;-) Moooooo. >> >> What about the attached one? I'm compiling it right now to test in UML :) >> >> [ snip fake-NUMA-on-SMP discussion ] >> > > OK, too quick for me... this next one applies, compiles and boots on > 2.5.66 + uml. Now I wonder how can I test if this is useful... ideas?
Well, benchmark it ;-) My favourite trick is to just "/usr/bin/time make bzImage" on some fixed kernel version & config, but aim7 / aim9 is pretty easy to set up too, and might be interesting.
M.
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