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Re: IBM system/360 ad

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Alexander Schreiber <als@usenet.thangorodrim.de> writes:
>J  Clarke <jclarke.873638@gmail.com> wrote:
>> On Wed, 27 Nov 2019 13:39:25 -0800 (PST), hancock4@bbs.cpcn.com wrote:
>>
>>>On Wednesday, November 27, 2019 at 4:23:02 PM UTC-5, Andy Burns wrote:
>>>> hancock4@bbs.cpcn.com wrote:
>>>> 
>>>> > Anyone know how much real memory does the Z series support today?
>>>> > Unlike the past, it's hard to get firm information from IBM
>>>> > on various models, even if they even have specific models.
>>>> 
>>>> 40TB
>>>> 
>>>> <https://www.mainline.com/ibm-z15-september-12-2019-announcement>
>>>> 
>>>> since that's in RAIM config, I assume less useable memory if you 
>>>> actually mirror/stripe/whatever it?
>>>
>>>OMG.
>>>
>>>But I must admit caching is nice.  First time I read a file
>>>it takes a minute or two.  But each successive access
>>>runs very fast.  I assumed the file is stored in memory
>>>in its entirety.
>>
>> I did an experiment many years ago.  I had two machines.  One was a 1
>> GHz Pentium and the other was a 450 MHz Xeon.  There was a particular
>> dataset and program that I was working with.  I noticed that the
>> dataset was larger than the cache on the Pentium but smaller than the
>> cache on the Xeon.  Same code, same OS, same as much else as possible,
>> the Xeon ran that particular program on that particular dataset twice
>> as fast.
>
>Yes, running pretty much entirely in cache is _great_ for performance.
>I've been told that during the days of the i486, the Linux scheduler
>was carefully optimized to fit entirely into < 8 KB of memory - because
>the i486 had 8 KB of cache.

I suspect that is an urban legend.  The scheduler is only needed infrequently,
and most of it doesn't run on context switches.

What your correspondent probably meant was the the frequently used parts
of the scheduler were crafted to consume only a couple of cache lines by
collecting the most commonly used code together; which would leave the
remaining cache lines (some occupied by shared kernel or libc code, others
by user code) in the cache even when scheduling a new thread on the core.

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IBM system/360 ad hancock4@bbs.cpcn.com - 2019-11-25 13:20 -0800
  Re: IBM system/360 ad Quadibloc <jsavard@ecn.ab.ca> - 2019-11-25 15:07 -0800
    Re: IBM system/360 ad Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2019-11-26 01:22 +0000
      Re: IBM system/360 ad hancock4@bbs.cpcn.com - 2019-11-27 12:54 -0800
        Re: IBM system/360 ad Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2019-11-28 18:08 +0000
      Re: IBM system/360 ad Ahem A Rivet's Shot <steveo@eircom.net> - 2019-11-28 09:44 +0000
        Re: IBM system/360 ad Peter Flass <peter_flass@yahoo.com> - 2019-11-28 11:04 -0700
  Re: IBM system/360 ad Anne & Lynn Wheeler <lynn@garlic.com> - 2019-11-25 14:41 -1000
    Re: IBM system/360 ad scott@slp53.sl.home (Scott Lurndal) - 2019-11-26 01:31 +0000
    Re: IBM system/360 ad hancock4@bbs.cpcn.com - 2019-11-27 12:49 -0800
      Re: IBM system/360 ad Andy Burns <usenet@andyburns.uk> - 2019-11-27 21:23 +0000
        Re: IBM system/360 ad hancock4@bbs.cpcn.com - 2019-11-27 13:39 -0800
          Re: IBM system/360 ad J. Clarke <jclarke.873638@gmail.com> - 2019-11-27 18:18 -0500
            Re: IBM system/360 ad Alexander Schreiber <als@usenet.thangorodrim.de> - 2019-12-02 00:23 +0100
              Re: IBM system/360 ad scott@slp53.sl.home (Scott Lurndal) - 2019-12-02 15:37 +0000
      Re: IBM system/360 ad David LaRue <huey.dll@tampabay.rr.com> - 2019-11-28 03:16 +0000
  Re: IBM system/360 ad David Wade <g4ugm@dave.invalid> - 2019-11-26 21:35 +0000
    Re: IBM system/360 ad Bob Eager <news0073@eager.cx> - 2019-11-26 22:21 +0000
    Re: IBM system/360 ad Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2019-11-26 22:50 +0000
      Re: IBM system/360 ad David Wade <g4ugm@dave.invalid> - 2019-11-27 00:41 +0000
        Re: IBM system/360 ad Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2019-11-27 05:49 +0000
          Re: IBM system/360 ad David Wade <g4ugm@dave.invalid> - 2019-11-27 11:22 +0000
            Re: IBM system/360 ad Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2019-11-27 19:54 +0000
              Re: IBM system/360 ad hancock4@bbs.cpcn.com - 2019-11-27 13:05 -0800
          Re: IBM system/360 ad hancock4@bbs.cpcn.com - 2019-11-27 13:04 -0800
            Re: IBM system/360 ad Anne & Lynn Wheeler <lynn@garlic.com> - 2019-11-27 13:11 -1000
            Re: IBM system/360 ad Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2019-11-28 18:08 +0000
              Re: IBM system/360 ad J. Clarke <jclarke.873638@gmail.com> - 2019-11-28 13:28 -0500
                Re: IBM system/360 ad Quadibloc <jsavard@ecn.ab.ca> - 2019-12-01 13:16 -0800
                Re: IBM system/360 ad Niklas Karlsson <anksil@yahoo.se> - 2019-12-03 15:14 +0000
                Re: IBM system/360 ad hancock4@bbs.cpcn.com - 2019-12-04 13:01 -0800
              Re: IBM system/360 ad Dan Espen <dan1espen@gmail.com> - 2019-11-28 19:41 -0500

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