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Re: Page sizes

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On Sat, 27 Jun 2020 15:10:22 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

>Hi George,
>
>Hope you are keeping well...  bad pandemic response, here; really
>high temperatures; increasing humidity; and lots of smoke in the
>air (but really cool "displays" at night!)  :<   Time to make some
>ice cream and enjoy the ride!  :>
>
>On 6/27/2020 2:37 PM, George Neuner wrote:
>> Hi Don,
>> On Fri, 26 Jun 2020 21:45:54 -0700, Don Y
>> <blockedofcourse@foo.invalid> wrote:
>> 
>>> Are there any processors/PMMUs for which the following would be
>>> true (nonzero)?
>>>
>>> (pagesize - 1) & pagesize
>> 
>> Not anything you can buy.
>
>I'm wondering if some of the "classic" designs might scale to newer
>device geometries better than some of the newer architectures?
>
>E.g., supporting ~100 (variable sized) segments concurrently and
>binding each to a particular "object" (for want of a better word).
>If the segment management hardware automatically reloads (in a manner
>similar to the TLBs functionality), then this should yield better
>(or comparable) performance to the fixed page-size approach (if
>you assume the fixed pages poorly "fit" the types of "objects"
>that you are mapping)
>
>[I think we discussed this -- or something similar -- a while ago]

About ~10 years ago  8-)

But you asked about "pages" here, which invariably are fixed sized
entities.  Arbitrarily sized "segments" are a different subject.

If you want a *useful* segmenting MMU, you probably need to design it
yourself.  Historically there were some units that did it (what I
would call) right, but none are scalable to modern memory sizes.

Whatever you do, you want the program to work with flat addresses and
have segmentation applied transparently (like paging) during memory
access.  You certainly DO NOT want to follow the x86 example of
exposing segments in the addressing.


>You still have a "packing problem" but with a virtual address space
>per process, you'd only have to address the "objects" with which a
>particular process interacted in any particular address space.
>And, that binding (for PIC) could be done at compile time *or*
>load time (the latter being more flexible) -- or even RUN-time!

George

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Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-26 21:45 -0700
  Re: Page sizes Bernd Linsel <bl1@gmx.com> - 2020-06-27 08:33 +0200
    Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-27 00:32 -0700
      Re: Page sizes Bernd Linsel <bl1@gmx.com> - 2020-06-27 12:21 +0200
        Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-27 15:12 -0700
        Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-27 18:14 -0400
      Re: Page sizes David Brown <david.brown@hesbynett.no> - 2020-06-27 17:21 +0200
        Re: Page sizes Clifford Heath <no.spam@please.net> - 2020-06-28 15:30 +1000
      Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-27 18:02 -0400
  Re: Page sizes upsidedown@downunder.com - 2020-06-27 11:11 +0300
  Re: Page sizes John Speth <johnspeth@yahoo.com> - 2020-06-27 07:59 -0700
  Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-27 17:37 -0400
    Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-27 15:10 -0700
      Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-27 18:35 -0400
        Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-27 16:36 -0700
          Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-28 01:01 -0400
            Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-27 23:50 -0700
              Re: Page sizes upsidedown@downunder.com - 2020-06-28 13:27 +0300
                Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-28 11:49 -0700
              Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-30 00:05 -0400
                Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-29 23:24 -0700
                Re: Page sizes upsidedown@downunder.com - 2020-06-30 11:00 +0300
                Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-30 12:23 -0700
                Re: Page sizes upsidedown@downunder.com - 2020-07-01 13:31 +0300
                Re: Page sizes Dimiter_Popoff <dp@tgi-sci.com> - 2020-07-01 19:44 +0300
                Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-30 05:45 -0400
                Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-30 04:13 -0700
                Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-06-30 12:49 -0400
                Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-30 12:44 -0700
                Re: Page sizes George Neuner <gneuner2@comcast.net> - 2020-07-02 03:14 -0400
        Re: Page sizes upsidedown@downunder.com - 2020-06-28 09:24 +0300
          Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-28 00:11 -0700
            Re: Page sizes upsidedown@downunder.com - 2020-06-28 15:59 +0300
              Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-28 12:04 -0700
                Re: Page sizes upsidedown@downunder.com - 2020-06-30 06:43 +0300
                Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-29 23:47 -0700
          Re: Page sizes Rick C <gnuarm.deletethisbit@gmail.com> - 2020-06-28 01:18 -0700
            Re: Page sizes upsidedown@downunder.com - 2020-06-28 16:29 +0300
              Re: Page sizes Don Y <blockedofcourse@foo.invalid> - 2020-06-28 12:18 -0700
  Re: Page sizes Richard Damon <Richard@Damon-Family.org> - 2020-06-27 18:27 -0400
  Re: Page sizes Andrew Smallshaw <andrews@sdf.org> - 2020-07-04 06:11 +0000

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