On 24 February 2010 14:11, Ben Kloosterman <[email protected]> wrote:
> But those same laptops will be running around with 4-16G RAM ( limited by
> batteries, desktops or severs will prob be 100G)  and 64 bit addressing .
> The counter question I raised was  is paging needed as you can persist data
> by other more flexible and more loosely coupled mechanisms   which may be
> slower if the device demands it .  Also solid state drives don’t reduce
> battery power when used which it will for paging , for smartphones this may
>  not be acceptable as the devices size is mainly limited by the battery for
> which we are likely to see little improvement in technology.
>
>
>
> With some doubt over the usefulness of paging ( well I have) why make paging
> a critical feature of an OS and worse tightly couple it to a GC , at the
> least you deny all devices today and in the future that have  no low latency
> secondary storage or which have secondary storage that needs to be quite for
> power reasons ?
>

How do you imagine a general purpose system without paging?

Paging is the mechanism for bridging the discrepancy between
relatively slow, large and permanent disk or other kind of bulk
storage and the relatively fast, small and ephemeral RAM.

As long as this discrepancy exists (that is until you can access any
storage attached to any computer on the internet within a few cpu
cycles) paging is needed.

Even if you get hundreds of gigabytes of RAM in any new system in a
few years who says you won't have hundreds of terabytes of disk size,
too? You can't then just read the whole disk into RAM.

There are also performance reasons. I would not want to see the
startup time of a system that reads my whole drive into the RAM.

Also I doubt that in a few years the RAM sizes will increase
dramatically. The current jump in RAM size is bought by lower
reliability which is bordering on too flaky and I guess the next step
would be to work on that, especially if reliable systems are available
which actually work reliably on reliable hardware.

Thanks

Michal

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