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From: | Christopher Dale |
Subject: | Re: [Gnu-arch-users] arch lkml |
Date: | Sat, 13 Dec 2003 05:48:42 +0900 |
User-agent: | Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.6a) Gecko/20031022 Thunderbird/0.4a (Gcc 3.3.1 i686 optimized - MozJF) |
Eric W. Biederman wrote:
Tom Lord <address@hidden> writes:* serendipitous archive-as-payloads So we're going to have long-lived client sites that pull updates or push updates to or from some archive host. In fact, we'll have _many_ such clients for our most interesting hosts.One idea is that we should, archive-side, just cache the payloads that we'll send to these clients -- so that when a client needs some"thing" we just find it on disk and stream it out.It turns out, then, that if instead of "caching" we simply "memoize" those payloads ("caching" can discard stuff -- "memoizing" holds onto it forever) that the memo we create contains, in a _reasonably_ compact form, all of the information we would have in an archive. So: the memo _is_ the archive. Disregarding archive-cached revisions for the moment, an arch archive _is_ just a memo of thepayloads that a client might ask for.That's dirt-simple to implement, allows arch to use "dumb servers", and is the same "big-O" space complexity as the more sophisticatedformats.I need to read through this one a little more. As I don't have a clear idea by what you mean with memorizing payloads.
I think the concept is that with a cache, the system (arbitrarily, from the user's POV) decides what objects are going to be cached (usually based on a most-recently-used or most-frequently-used algorithm) and when they are going to be 'uncached' (usually cached objects are dropped when they become old or unpopular, i.e. the caching algorithm in reverse).
Whereas, with the "memoizing" (no "r"!) concept, the memoized objects are (presumably) explicitly decided (in the arch context the aim would be to identify and memoize "useful" payloads) and then kept forever (or at least until explicitly dropped).
You would expect that the contents of an active arch archive server cache would pretty closely mirror the equivalent "memo-box" (?), with the important exception that certain infrequently requested (but hideously useful) archive revisions could be found in the "memo-box" but not in the cache.
IOW, the "memo-box" is a cache equivalent/replacement, and indeed a hybrid cache+memo-box (= cache with the ability to import & mark certain cached items as "persistant") might be the best solution of all.
Then again, I could be wrong, yrs k, etc. Chris(Doh! Always try google first: http://search.cpan.org/dist/Memoize/Memoize.pm
it does seem to be the same basic idea though!)
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