Messages in this thread | | | Date | Tue, 31 Jan 2006 20:06:10 -0800 | From | "Barry K. Nathan" <> | Subject | Re: [RFC] VM: I have a dream... |
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On 1/31/06, Al Boldi <a1426z@gawab.com> wrote: > Faulty, because we are currently running a legacy solution to workaround an > 8,16,(32) arch bits address space limitation, which does not exist in > 64bits+ archs for most purposes.
In the early 1990's (and maybe even the mid 90's), the typical hard disk's storage could theoretically be byte-addressed using 32-bit addresses -- just as (if I understand you correctly) you are arguing that today's hard disks can be byte-addressed using 64-bit addresses.
If this was going to be practical ever (on commodity hardware anyway), I would have expected someone to try it on a 32-bit PC or Mac when hard drives were in the 100MB-3GB range... That suggests to me that there's a more fundamental reason (i.e. other than lack of address space) that caused people to stick with the current scheme.
[snip] > There is a lot to gain, for one there is no more swapping w/ all its related > side-effects. You're dealing with memory only. You can also run your fs > inside memory, like tmpfs, which is definitely faster. And there may be > lots of other advantages, due to the simplified architecture applied.
tmpfs isn't "definitely faster". Remember those benchmarks where Linux ext2 beat Solaris tmpfs? http://www.tux.org/lkml/#s9-12
Also, the only way I see where "there is no more swapping" and "[y]ou're dealing with memory only" is if the disk *becomes* main memory, and main memory becomes an L3 (or L4) cache for the CPU [and as a consequence, main memory also becomes the main form of long-term storage]. Is that what you're proposing?
If so, then it actually makes *less* sense to me than before -- with your scheme, you've reduced the speed of main memory by 100x or more, then you try to compensate with a huge cache. IOW, you've reduced the speed of *main* memory to (more or less) the speed of today's swap! Suddenly it doesn't sound so good anymore...
-- -Barry K. Nathan <barryn@pobox.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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