4 ms·

Not realtime, because that only enforces 'precision', not low latency per se. When I was working in this field, 2008-2011, there were guys doing fpgas, custom

Not realtime, because that only enforces 'precision', not low latency per se. When I was working in this field, 2008-2011, there were guys doing fpgas, custom tcp/ip stacks, custom network drivers, dedicated networks and network cards for exchange data coming in and for going out. Mostly linux. Hardware and lowlevel fun. Allthough the fastest trades were always done by this one catalonian guy using Windows and .NET. I kid you not. Good times. Soulless. But good.

exikyut 8y ago
How does realtime enforce precision and not latency? I was referring to hard realtime. And wow, so I wasn't too far off the mark. FPGAs and exotic networking. Huh. I remember reading a story about a trading floor running on SQL Server, which was doing continuous throughput of 6000 queries/second. I didn't know enough at the time to discern what percentage of that was writes, but I think the point may have been that it was all of it. This was quite a few years ago. So perhaps Windows isn't actually the slowe{st,r} system out there for certain tasks.
- mverwijs 8y ago
  As I've always understood (but I'm no RTOS expert) is that RTOS does not guarantee LOWER latency. It guarantees A latency. But again: not an RTOS expert. We had a lab that would constantly test configurations of hardware and software. And I remember them finding RTOS not being helpful.
  - planteen 8y ago
    That's right, real-time does not mean real-fast. In a hard real-time system, there is a deterministic worst-case bound for response times. "Real fast" CPUs, like the latest and greatest Intel CPUs, are actually pretty difficult to get deterministic bounds on. There are factors like unpreventable SMI events, possibility of L1/L2/L3 cache misses, etc. Often systems that need to be really deterministic, like say an engine controller in a car, run on simple CPUs like the Cortex-R series from ARM.
    - exikyut 8y ago
      > "Real fast" CPUs, like the latest and greatest Intel CPUs, are actually pretty difficult to get deterministic bounds on. There are factors like unpreventable SMI events, possibility of L1/L2/L3 cache misses, etc. Oh yeah. I remember reading something along the same lines about x86 a while back. I guess it didn't really go in properly, heh. Thanks I'm reminded of the "x86 is high level" thing: https://news.ycombinator.com/item?id=9264195 https://news.ycombinator.com/item?id=9264195 Also, I think the iPhone 6's NVMe apparently uses a Cortex-R: https://ramtin-amin.fr/#nvmepcie https://ramtin-amin.fr/#nvmepcie

exikyut 8y ago

How does realtime enforce precision and not latency? I was referring to hard realtime. And wow, so I wasn't too far off the mark. FPGAs and exotic networking. Huh. I remember reading a story about a trading floor running on SQL Server, which was doing continuous throughput of 6000 queries/second. I didn't know enough at the time to discern what percentage of that was writes, but I think the point may have been that it was all of it. This was quite a few years ago. So perhaps Windows isn't actually the slowe{st,r} system out there for certain tasks.

mverwijs 8y ago
As I've always understood (but I'm no RTOS expert) is that RTOS does not guarantee LOWER latency. It guarantees A latency. But again: not an RTOS expert. We had a lab that would constantly test configurations of hardware and software. And I remember them finding RTOS not being helpful.
- planteen 8y ago
  That's right, real-time does not mean real-fast. In a hard real-time system, there is a deterministic worst-case bound for response times. "Real fast" CPUs, like the latest and greatest Intel CPUs, are actually pretty difficult to get deterministic bounds on. There are factors like unpreventable SMI events, possibility of L1/L2/L3 cache misses, etc. Often systems that need to be really deterministic, like say an engine controller in a car, run on simple CPUs like the Cortex-R series from ARM.
  - exikyut 8y ago
    > "Real fast" CPUs, like the latest and greatest Intel CPUs, are actually pretty difficult to get deterministic bounds on. There are factors like unpreventable SMI events, possibility of L1/L2/L3 cache misses, etc. Oh yeah. I remember reading something along the same lines about x86 a while back. I guess it didn't really go in properly, heh. Thanks I'm reminded of the "x86 is high level" thing: https://news.ycombinator.com/item?id=9264195 https://news.ycombinator.com/item?id=9264195 Also, I think the iPhone 6's NVMe apparently uses a Cortex-R: https://ramtin-amin.fr/#nvmepcie https://ramtin-amin.fr/#nvmepcie