4K pages probably used to be too large

By: Ben LaHaise (bcrl.delete@this.kvack.org), May 2, 2021 9:45 am
Room: Moderated Discussions
Yuhong Bao (yuhongbao_386.delete@this.hotmail.com) on May 1, 2021 1:01 pm wrote:
> The fun thing is that 4K pages probably used to be too large. On a 80386, just 8 tasks would consume
> at least 64k and probably 128k just for the page tables alone. (80386 page tables were two levels)

The National Semiconductor 32016 had 512 byte page sizes. The problem is that overhead of small page sizes becomes excessive as soon as you have more than a couple of megabytes of memory. With 16MB of RAM and 512 byte pages that works out to 65536 pages for which data structures to track all the individual pages are needed. Even at 16 bytes of overhead per page, that's 1MB or 1/16th of memory. For reference Linux has upwards of 64 byte of overhead per page these days. The window for which 512 byte pages were viable was closed back in the 1980s.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
4K pages probably used to be too largeYuhong Bao2021/05/01 12:01 PM
  HDD seek time isn't freeMark Roulo2021/05/01 01:12 PM
    HDD seek time isn't freeYuhong Bao2021/05/01 01:21 PM
      HDD seek time isn't freeTim Mc2021/05/01 01:42 PM
        HDD seek time isn't freerwessel2021/05/01 01:57 PM
  4K pages probably used to be too largeBen LaHaise2021/05/02 09:45 AM
    VAX was 512 (in 1977) (NT)anonymous22021/05/02 07:36 PM
      FWIW, S/370 offered a choice of 2K and 4K (NT)rwessel2021/05/03 04:09 AM
      DEC's earliest PDP-11 disks were 512 (in 1971)John Yates2021/05/03 12:53 PM
    4K pages probably used to be too largeanon22021/05/03 12:17 AM
      4K pages probably used to be too largeBen LaHaise2021/05/03 04:36 PM
        Morotola 680x0 series page sizesBen LaHaise2021/05/03 04:51 PM
        4K pages probably used to be too largeanon22021/05/03 05:39 PM
          4K pages probably used to be too largeanon22021/05/03 07:51 PM
        4K pages probably used to be too largeYuhong Bao2021/05/03 09:51 PM
      4K pages probably used to be too largewumpus2021/05/05 08:06 AM
        4K pages probably used to be too largeanon22021/05/05 03:04 PM
          4K pages probably used to be too largeChester2021/05/05 05:45 PM
            4K pages probably used to be too largewumpus2021/05/06 08:06 AM
              Phenom TLB bugHeikki Kultala2021/05/06 11:46 AM
                Phenom TLB bugChester2021/05/06 04:29 PM
        4K pages probably used to be too largeEtienne Lorrain2021/05/06 12:08 AM
          4K pages probably used to be too largeJames2021/05/06 01:36 AM
            4K pages probably used to be too largerwessel2021/05/06 08:32 AM
              Reformatting SCSI disk sector sizeDoug S2021/05/06 10:30 AM
        4K pages probably used to be too largeDavid Hess2021/05/11 07:57 AM
  Page size is more complex/nuancedPaul A. Clayton2021/05/08 09:03 AM
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