Crazy CXL Names

By: Michael S (already5chosen.delete@this.yahoo.com), May 31, 2022 3:07 am
Room: Moderated Discussions
Peter Lewis (peter.delete@this.notyahoo.com) on May 31, 2022 2:24 am wrote:
> > Full cache coherence over high-latency link is a horrible, horrible, horrible idea.
>
> Please explain or provide a link.

There is nothing to explain.
Just think about what happens in system in presence of coherent device connected through slow link at each cache miss that also missed coherence filter/cache directory.
Answer: instead of 50-55 ns CPU waits 1000-1500 ns.

> I imagine poorly written software could be very slow, but
> that is always a problem.

Totally unrelated software that does not even know or care about the presence of new cache-coherent device in the system could suddenly become very slow.

> Is the issue that it would not be obvious that some code will be
> very slow? Even within a multicore processor, programmers have to be careful to avoid having
> two different cores repeatedly write different parts of the same cache line to prevent the
> cache line from bouncing back and forth between their caches (called false sharing).
>
> > What is CXL.io ? From the name alone I can't figure out. Going
> > by name it sounds *exactly* the same as normal PCIe.
>
> According to Wikipedia, CXL.io is “based on PCIe 5.0 with a few enhancements, it provides
> configuration, link initialization and management, device discovery and enumeration,
> interrupts, DMA, and register I/O access using non-coherent loads/stores”.

Sounds the same as PCIe.

< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Crazy CXL NamesPeter Lewis2022/05/30 03:54 PM
  Crazy CXL Namesanon22022/05/30 07:19 PM
    Crazy CXL NamesPeter Lewis2022/05/30 09:30 PM
      Crazy CXL Namesanon22022/05/31 02:24 AM
        Crazy CXL NamesPeter Lewis2022/05/31 02:43 AM
          Crazy CXL Namesanon22022/05/31 03:01 AM
            Crazy CXL NamesPeter Lewis2022/05/31 03:36 AM
              Crazy CXL Namesanon22022/05/31 04:32 AM
                Crazy CXL NamesPeter Lewis2022/05/31 05:21 AM
                  Crazy CXL Namesanon22022/05/31 06:03 AM
                    Crazy CXL NamesPeter Lewis2022/05/31 04:27 PM
                      Crazy CXL Namesanon22022/05/31 04:58 PM
                      Crazy CXL Namesgoose2022/05/31 05:35 PM
                        Crazy CXL NamesPeter Lewis2022/06/03 03:10 AM
                          Reason for Crazy CXL NamesGary Kopp2022/06/24 01:43 PM
                            Reason for Crazy CXL Namesdmcq2022/06/25 11:18 AM
                              Reason for Crazy CXL NamesMichael S2022/06/26 01:30 AM
                                Reason for Crazy CXL NamesDummond D. Slow2022/06/26 06:49 AM
                                  Reason for Crazy CXL NamesMichael S2022/06/26 07:32 AM
                                    Reason for Crazy CXL Namesdmcq2022/06/26 11:54 AM
                                Reason for Crazy CXL Namesanon22022/06/26 03:26 PM
                                  Reason for Crazy CXL NamesEric P2022/07/01 02:48 PM
                                    Reason for Crazy CXL Namesanon22022/07/01 07:56 PM
                                      Reason for Crazy CXL NamesGroo2022/07/02 05:13 AM
                                    Reason for Crazy CXL NamesUngo2022/07/01 11:14 PM
                                      Reason for Crazy CXL NamesEric P2022/07/05 03:21 AM
                      Crazy CXL NamesDoug S2022/06/01 12:44 AM
    Crazy CXL NamesMichael S2022/05/31 01:21 AM
      Crazy CXL Namesanon22022/05/31 02:20 AM
      Crazy CXL NamesPeter Lewis2022/05/31 02:24 AM
        Crazy CXL NamesMichael S2022/05/31 03:07 AM
          Crazy CXL NamesPeter Lewis2022/05/31 04:37 AM
            Current NVidia GPU Launch Latency: 10 microsecondsMark Roulo2022/05/31 01:07 PM
              Current NVidia GPU Launch Latency: 10 microsecondsFreddie2022/06/01 09:44 AM
      Crazy CXL Names---2022/05/31 07:56 PM
        Crazy CXL Namesaaron spink2022/05/31 08:32 PM
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