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Groups > alt.os.linux > #51787
| From | William Unruh <unruh@invalid.ca> |
|---|---|
| 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 13:53 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <ptbl5c$22p$1@dont-email.me> (permalink) |
| References | (9 earlier) <pt3ima$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.
On 2018-11-24, 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: >>> On 21/11/2018 13:24, Richard Kettlewell wrote: >>>> Rich <rich@example.invalid> writes: >>>>> In comp.os.linux.misc The Natural Philosopher <tnp@invalid.invalid> wrote: >>>>>> Intersting that people differentiate between 'speculative execution' and >>>>>> 'caching'. >>>>>> >>>>>> Or is caching 'speculative memory access' as opposed to 'speculative >>>>>> execution'? >>>>> >>>>> You could call it (caching) that (speculative memory access). >>>>> >>>>> Caching works on the principal that most programs often access memory >>>>> addresses that are nearby other memory addresses previously accessed by >>>>> the same program. I.e., consider walking an array (X[0] ... X[100]) >>>>> and doing something. First access is to X[0], second to X[1], third to >>>>> X[2] and so on. Caching works because when the program reads X[0] the >>>>> cache actually reads in memory that holds X[0]...X[10]. So now >>>>> accesses to X[1]...X[10] happen from the cache instead of each directly >>>>> from main memory. >>>> >>>> That’s certainly a useful outcome of the way memory access works, but >>>> it’s not inherent to caching. A CPU could (hypothetically) cache >>>> individual words and still get a (smaller) performance improvement from >>>> the cache hits. Moreover in the context of this thread it’s the caching >>>> as such, rather than the bulk reads, that leads to the cache being >>>> usable as a communication channel. >>>> >>>> Analogously, disk reads typically happen in 512-byte or 4096-byte blocks >>>> (at a minimum), but when we talk about filesystem caching, we don’t mean >>>> that bulk I/O, we mean the OS keeping large numbers of those blocks in >>>> RAM to avoid having to read them again in the near future. >>>> >>>> At any rate conflating caching with speculative execution is a >>>> non-starter. >>>> >>> 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 The point of speculative execution is not storage, but execution. Yes, the result gets stored in the cpu but that storage is not the purpose. The purpose is the exectution of the instructions that are not yet called for. > 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. An example of why "Philosophical" often gets such a bad rap. > > >>> >>> > >
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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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