By: Gabriele Svelto (gabriele.svelto.delete@this.gmail.com), August 21, 2018 2:54 pm
Room: Moderated Discussions
Linus Torvalds (torvalds.delete@this.linux-foundation.org) on August 21, 2018 3:31 pm wrote:
> So you can solve it other ways. One way is to have the remote atomics, and just do the statistics update
> "somewhere else" and asynchronously. That's a lovely model in many ways, but it's not portable.
The only implementation of that I know of are in Freescale's POWER network processors. They added remote atomics which they advertised specifically for use in statistics. IIRC the actual operations were executed in the L3 cache. They worked by setting up a cache-inhibited range of memory and then used what they called "decorated operations" (i.e. loads or stores plus an operation) to access it; you couldn't access the same area as cached memory, it just didn't work. Here's some more info:
Decorated Operations for QorIQ P3/P4/P5 Processors
One big downside they had was that they could not be executed speculatively, they were effectively serializing instructions. The issue was that a speculatively executed instruction would trigger an atomic operation even if the instruction was later squashed if the speculation turned out to be wrong. The remote atomic machinery had no access to the core and thus no way to know that the instruction had been squashed, and would merrily execute it anyway.
> So you can solve it other ways. One way is to have the remote atomics, and just do the statistics update
> "somewhere else" and asynchronously. That's a lovely model in many ways, but it's not portable.
The only implementation of that I know of are in Freescale's POWER network processors. They added remote atomics which they advertised specifically for use in statistics. IIRC the actual operations were executed in the L3 cache. They worked by setting up a cache-inhibited range of memory and then used what they called "decorated operations" (i.e. loads or stores plus an operation) to access it; you couldn't access the same area as cached memory, it just didn't work. Here's some more info:
Decorated Operations for QorIQ P3/P4/P5 Processors
One big downside they had was that they could not be executed speculatively, they were effectively serializing instructions. The issue was that a speculatively executed instruction would trigger an atomic operation even if the instruction was later squashed if the speculation turned out to be wrong. The remote atomic machinery had no access to the core and thus no way to know that the instruction had been squashed, and would merrily execute it anyway.
Topic | Posted By | Date |
---|---|---|
ARM turns to a god and a hero | AM | 2018/08/16 08:32 AM |
ARM turns to a god and a hero | Maynard Handley | 2018/08/16 08:41 AM |
ARM turns to a god and a hero | Doug S | 2018/08/16 10:11 AM |
ARM turns to a god and a hero | Geoff Langdale | 2018/08/16 10:59 PM |
ARM turns to a god and a hero | dmcq | 2018/08/17 04:12 AM |
ARM is somewhat misleading | Adrian | 2018/08/16 10:56 PM |
It's marketing material | Gabriele Svelto | 2018/08/17 12:00 AM |
It's marketing material | Michael S | 2018/08/17 02:13 AM |
It's marketing material | dmcq | 2018/08/17 04:23 AM |
It's marketing material | Andrei Frumusanu | 2018/08/17 06:25 AM |
It's marketing material | Linus Torvalds | 2018/08/17 10:20 AM |
It's marketing material | Groo | 2018/08/17 12:44 PM |
It's marketing material | Doug S | 2018/08/17 01:14 PM |
promises and deliveries | AM | 2018/08/17 01:32 PM |
promises and deliveries | Passing Through | 2018/08/17 02:02 PM |
Just by way of clarification | Passing Through | 2018/08/17 02:15 PM |
Just by way of clarification | AM | 2018/08/18 11:49 AM |
Just by way of clarification | Passing Through | 2018/08/18 12:34 PM |
This ain't the nineties any longer | Passing Through | 2018/08/18 12:54 PM |
This ain't the nineties any longer | Maynard Handley | 2018/08/18 01:50 PM |
This ain't the nineties any longer | Passing Through | 2018/08/18 02:57 PM |
This ain't the nineties any longer | Passing Through | 2018/09/06 01:42 PM |
This ain't the nineties any longer | Maynard Handley | 2018/09/07 03:10 PM |
This ain't the nineties any longer | Passing Through | 2018/09/07 03:48 PM |
This ain't the nineties any longer | Maynard Handley | 2018/09/07 04:22 PM |
Just by way of clarification | Wilco | 2018/08/18 12:26 PM |
Just by way of clarification | Passing Through | 2018/08/18 12:39 PM |
Just by way of clarification | none | 2018/08/18 09:52 PM |
Just by way of clarification | dmcq | 2018/08/19 07:32 AM |
Just by way of clarification | none | 2018/08/19 07:54 AM |
Just by way of clarification | dmcq | 2018/08/19 10:24 AM |
Just by way of clarification | none | 2018/08/19 10:52 AM |
Just by way of clarification | Gabriele Svelto | 2018/08/19 05:41 AM |
Just by way of clarification | Passing Through | 2018/08/19 08:25 AM |
Whiteboards at Gatwick airport anyone? | Passing Through | 2018/08/20 03:24 AM |
It's marketing material | Michael S | 2018/08/18 10:12 AM |
It's marketing material | Brett | 2018/08/18 04:22 PM |
It's marketing material | Brett | 2018/08/18 04:33 PM |
It's marketing material | Adrian | 2018/08/19 12:21 AM |
A76 | AM | 2018/08/17 01:45 PM |
A76 | Michael S | 2018/08/18 10:20 AM |
A76 | AM | 2018/08/18 11:39 AM |
A76 | Michael S | 2018/08/18 11:49 AM |
A76 | AM | 2018/08/18 12:06 PM |
A76 | Doug S | 2018/08/18 12:43 PM |
A76 | Maynard Handley | 2018/08/18 01:42 PM |
A76 | Maynard Handley | 2018/08/18 03:22 PM |
Why write zeros when one can use metadata? | Paul A. Clayton | 2018/08/18 05:19 PM |
Why write zeros when one can use metadata? | Maynard Handley | 2018/08/19 10:12 AM |
Dictionary compress might apply to memcopy | Paul A. Clayton | 2018/08/19 12:45 PM |
Instructions for zeroing | Konrad Schwarz | 2018/08/30 05:37 AM |
Instructions for zeroing | Maynard Handley | 2018/08/30 07:41 AM |
Instructions for zeroing | Adrian | 2018/08/30 10:37 AM |
dcbz -> dcbzl (was: Instructions for zeroing) | hobold | 2018/08/31 12:50 AM |
dcbz -> dcbzl (was: Instructions for zeroing) | dmcq | 2018/09/01 04:28 AM |
A76 | Travis | 2018/08/19 10:36 AM |
A76 | Maynard Handley | 2018/08/19 11:22 AM |
A76 | Travis | 2018/08/19 01:07 PM |
A76 | Maynard Handley | 2018/08/19 05:24 PM |
Remote atomics | matthew | 2018/08/19 11:51 AM |
Remote atomics | Michael S | 2018/08/19 12:58 PM |
Remote atomics | matthew | 2018/08/19 01:32 PM |
Remote atomics | Michael S | 2018/08/19 01:36 PM |
Remote atomics | matthew | 2018/08/19 01:48 PM |
Remote atomics | Michael S | 2018/08/19 02:16 PM |
Remote atomics | Ricardo B | 2018/08/20 09:05 AM |
Remote atomics | dmcq | 2018/08/19 01:33 PM |
Remote atomics | Travis | 2018/08/19 01:32 PM |
Remote atomics | Michael S | 2018/08/19 01:46 PM |
Remote atomics | Travis | 2018/08/19 04:35 PM |
Remote atomics | Michael S | 2018/08/20 02:29 AM |
Remote atomics | matthew | 2018/08/19 06:58 PM |
Remote atomics | anon | 2018/08/19 11:59 PM |
Remote atomics | Travis | 2018/08/20 09:26 AM |
Remote atomics | Travis | 2018/08/20 08:57 AM |
Remote atomics | Linus Torvalds | 2018/08/20 03:29 PM |
Fitting time slices to execution phases | Paul A. Clayton | 2018/08/21 08:09 AM |
Fitting time slices to execution phases | Linus Torvalds | 2018/08/21 01:34 PM |
Fitting time slices to execution phases | Linus Torvalds | 2018/08/21 02:31 PM |
Fitting time slices to execution phases | Gabriele Svelto | 2018/08/21 02:54 PM |
Fitting time slices to execution phases | Linus Torvalds | 2018/08/21 03:26 PM |
Fitting time slices to execution phases | Travis | 2018/08/21 03:21 PM |
Fitting time slices to execution phases | Linus Torvalds | 2018/08/21 03:39 PM |
Fitting time slices to execution phases | Travis | 2018/08/21 03:59 PM |
Fitting time slices to execution phases | Linus Torvalds | 2018/08/21 04:13 PM |
Fitting time slices to execution phases | anon | 2018/08/21 03:27 PM |
Fitting time slices to execution phases | Linus Torvalds | 2018/08/21 05:02 PM |
Fitting time slices to execution phases | Etienne | 2018/08/22 01:28 AM |
Fitting time slices to execution phases | Gabriele Svelto | 2018/08/22 02:07 PM |
Fitting time slices to execution phases | Travis | 2018/08/22 03:00 PM |
Fitting time slices to execution phases | anon | 2018/08/22 05:52 PM |
Fitting time slices to execution phases | Travis | 2018/08/21 03:37 PM |
Is preventing misuse that complex? | Paul A. Clayton | 2018/08/23 04:42 AM |
Is preventing misuse that complex? | Linus Torvalds | 2018/08/23 11:46 AM |
Is preventing misuse that complex? | Travis | 2018/08/23 12:29 PM |
Is preventing misuse that complex? | Travis | 2018/08/23 12:33 PM |
Is preventing misuse that complex? | Jeff S. | 2018/08/24 06:57 AM |
Is preventing misuse that complex? | Travis | 2018/08/24 07:47 AM |
Is preventing misuse that complex? | Linus Torvalds | 2018/08/23 01:30 PM |
Is preventing misuse that complex? | Travis | 2018/08/23 02:11 PM |
Is preventing misuse that complex? | Linus Torvalds | 2018/08/24 12:00 PM |
Is preventing misuse that complex? | Gabriele Svelto | 2018/08/24 12:25 PM |
Is preventing misuse that complex? | Linus Torvalds | 2018/08/24 12:33 PM |
Fitting time slices to execution phases | Travis | 2018/08/21 02:54 PM |
rseq: holy grail rwlock? | Travis | 2018/08/21 02:18 PM |
rseq: holy grail rwlock? | Linus Torvalds | 2018/08/21 02:59 PM |
rseq: holy grail rwlock? | Travis | 2018/08/21 03:27 PM |
rseq: holy grail rwlock? | Linus Torvalds | 2018/08/21 04:10 PM |
rseq: holy grail rwlock? | Travis | 2018/08/21 05:21 PM |
ARM design houses | Michael S | 2018/08/21 04:07 AM |
ARM design houses | Wilco | 2018/08/22 11:38 AM |
ARM design houses | Michael S | 2018/08/22 01:21 PM |
ARM design houses | Wilco | 2018/08/22 02:23 PM |
ARM design houses | Michael S | 2018/08/29 12:58 AM |
Qualcomm's core naming scheme really, really sucks | Heikki Kultala | 2018/08/29 01:19 AM |
A76 | Maynard Handley | 2018/08/18 01:07 PM |
A76 | Michael S | 2018/08/18 01:32 PM |
A76 | Maynard Handley | 2018/08/18 01:52 PM |
A76 | Michael S | 2018/08/18 02:04 PM |
ARM is somewhat misleading | juanrga | 2018/08/17 12:20 AM |
Surprised?? | Alberto | 2018/08/17 12:52 AM |
Surprised?? | Alberto | 2018/08/17 01:10 AM |
Surprised?? | none | 2018/08/17 01:46 AM |
Garbage talk | Andrei Frumusanu | 2018/08/17 06:30 AM |
Garbage talk | Michael S | 2018/08/17 06:43 AM |
Garbage talk | Andrei Frumusanu | 2018/08/17 08:51 AM |
Garbage talk | Michael S | 2018/08/18 10:29 AM |
Garbage talk | Adrian | 2018/08/17 07:28 AM |
Garbage talk | Alberto | 2018/08/17 08:20 AM |
Garbage talk | Andrei Frumusanu | 2018/08/17 08:48 AM |
Garbage talk | Adrian | 2018/08/17 09:17 AM |
Garbage talk | Andrei Frumusanu | 2018/08/17 09:36 AM |
Garbage talk | Adrian | 2018/08/17 01:53 PM |
Garbage talk | Andrei Frumusanu | 2018/08/17 11:17 PM |
More like a religion he?? ARM has an easy life :) | Alberto | 2018/08/17 08:13 AM |
More like a religion he?? ARM has an easy life :) | Andrei Frumusanu | 2018/08/17 08:34 AM |
More like a religion he?? ARM has an easy life :) | Alberto | 2018/08/17 09:03 AM |
More like a religion he?? ARM has an easy life :) | Andrei Frumusanu | 2018/08/17 09:43 AM |
More like a religion he?? ARM has an easy life :) | Doug S | 2018/08/17 01:17 PM |
15W phone SoCs | AM | 2018/08/17 02:04 PM |
More like a religion he?? ARM has an easy life :) | Maynard Handley | 2018/08/17 11:29 AM |
my future stuff will be better than your old stuff, hey I'm a god at last (NT) | Eric Bron | 2018/08/18 02:34 AM |
my future stuff will be better than your old stuff, hey I'm a god at last | none | 2018/08/18 07:34 AM |