Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs

From	Rich <rich@example.invalid>
Newsgroups	alt.os.linux, comp.os.linux.misc
Subject	Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs
Date	2018-11-24 15:24 +0000
Organization	A noiseless patient Spider
Message-ID	<ptbqeo$he0$1@dont-email.me> (permalink)
References	(9 earlier) <pt3ima$qp6$1@dont-email.me> <87sgzud0mz.fsf@LkoBDZeT.terraraq.uk> <pt4l0d$r33$1@dont-email.me> <pt4r58$rne$1@dont-email.me> <ptbdls$udo$1@dont-email.me>

Cross-posted to 2 groups.

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In comp.os.linux.misc The Natural Philosopher <tnp@invalid.invalid> wrote:
> On 21/11/2018 23:53, William Unruh wrote:
>> On 2018-11-21, The Natural Philosopher <tnp@invalid.invalid> wrote:
>>> My statement was more semantic than technical
>> 
>> ???? It is not correct sematically (whatever you mean by that) either.
> 
> Oh it is.
> 
> Speculative executins get stored - cached in case trhey are needed
> Memory contents get strored - cached - in case they are needed
> Disc sectors get stored - cached - ion case they are needed
> 
> speculative execution/speculative memory read/speculative disc read.
> 
> I dont see any difference philosophicallyu - just at implementation 
> level.

Then you are utilizing a definition of cache that is too generic and is 
at odds with what computer artichitects use for the definition of 
cache.

Caching is not "storage until needed".

Rather caching is maintaining a *copy* of slow "storage" in a faster 
"storage" upon first access to slow storage for the purpose of making 
subsequent access (accesses 2...n) to the same storage area faster.  
The copy aspect is somewhat critical to grasp here.

For both memory contents and disk contents, this is what happens.  The 
cache stores a second *copy* of memory (or a second *copy* of disk) in 
a storage until that is faster to access than the master copy.

This also means (assuming that the cache is write through) that the 
contents of cache can be deleted at any time, with no effect on the 
state of the computer (only an effect on the net performance).

Speculative execution results are "stored" yes, but not as a *copy* of 
another memory, and not for accelerating access to the stored data for 
*subsequent accesses to that same data*.  Speculative execution results 
are are not a copy of any other storage while they are stored, and they 
are utilized exactly once, when the decision is made that the results 
should be used, else they are simply thrown away.

And, deletion of speculative execution results before they would 
otherwise be utilized would result in a different program state, 
because the only copy of the pre-computed state would have been 
deleted.

Thread

Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Nomen Nescio <noreply@mixnym.net> - 2018-11-16 20:21 -0600
  Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "J.O. Aho" <user@example.net> - 2018-11-17 11:10 +0100
    Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "Carlos E.R." <robin_listas@es.invalid> - 2018-11-17 11:26 +0100
      Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Richard Kettlewell <invalid@invalid.invalid> - 2018-11-17 11:53 +0000
        Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "Carlos E.R." <robin_listas@es.invalid> - 2018-11-18 21:06 +0100
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Paul <nospam@needed.invalid> - 2018-11-18 15:46 -0500
            Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Bud Frede <frede@mouse-potato.com> - 2018-11-24 09:07 -0500
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "J.O. Aho" <user@example.net> - 2018-11-18 22:27 +0100
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Richard Kettlewell <invalid@invalid.invalid> - 2018-11-19 08:27 +0000
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-19 18:33 +0000
            Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "J.O. Aho" <user@example.net> - 2018-11-19 21:02 +0100
              Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-20 04:46 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "J.O. Aho" <user@example.net> - 2018-11-20 06:59 +0100
            Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs not@telling.you.invalid (Computer Nerd Kev) - 2018-11-19 21:58 +0000
              Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2018-11-19 17:27 -0500
            Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2018-11-19 17:37 -0500
              Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Richard Kettlewell <invalid@invalid.invalid> - 2018-11-20 10:10 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Andreas Kohlbach <ank@spamfence.net> - 2018-11-20 15:51 -0500
              Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs not@telling.you.invalid (Computer Nerd Kev) - 2018-11-20 21:31 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Rich <rich@example.invalid> - 2018-11-20 23:14 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-21 06:50 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Paul <nospam@needed.invalid> - 2018-11-21 04:24 -0500
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Richard Kettlewell <invalid@invalid.invalid> - 2018-11-21 10:56 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Rich <rich@example.invalid> - 2018-11-21 12:22 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Richard Kettlewell <invalid@invalid.invalid> - 2018-11-21 13:24 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-21 22:08 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs William Unruh <unruh@invalid.ca> - 2018-11-21 23:53 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-24 11:46 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs William Unruh <unruh@invalid.ca> - 2018-11-24 13:53 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-24 18:39 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Andreas Kohlbach <ank@spamfence.net> - 2018-11-24 15:47 -0500
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-11-25 07:51 +0000
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Andreas Kohlbach <ank@spamfence.net> - 2018-11-25 16:08 -0500
                Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Rich <rich@example.invalid> - 2018-11-24 15:24 +0000
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Soviet_Mario <SovietMario@CCCP.MIR> - 2018-11-30 11:32 +0100
            Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs The Natural Philosopher <tnp@invalid.invalid> - 2018-12-01 05:13 +0000
    Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "Anonymous Remailer (austria)" <mixmaster@remailer.privacy.at> - 2018-11-18 06:23 +0100
      Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Jens Stuckelberger <Jens_Stuckelberger@nowhere.net> - 2018-11-19 19:06 +0000
        Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Anonymous <anonymous@hoi-polloi.org> - 2018-11-19 21:44 +0100
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Nomen Nescio <nobody@dizum.com> - 2018-11-20 10:19 +0100
        Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Dave Froble <davef@tsoft-inc.com> - 2018-11-19 18:44 -0500
          Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs kludge@panix.com (Scott Dorsey) - 2018-11-19 19:00 -0500
            Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Bobbie Sellers <bliss@mouse-potato.com> - 2018-11-26 20:40 -0800
        Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Nomen Nescio <nobody@dizum.com> - 2018-11-20 10:09 +0100
    Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs fr314159@gmail.com - 2018-11-28 07:26 -0800
      Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Jasen Betts <jasen@xnet.co.nz> - 2018-11-29 19:45 +0000
        Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs Melzzzzz <Melzzzzz@zzzzz.com> - 2018-11-29 20:21 +0000
        Re: Linux 4.20 is Running Slower Than 4.19 On Intel CPUs "F. Russell" <fr@random.info> - 2018-11-29 20:26 +0000

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