[time-nuts] PCI-E Serial Card For Windows NTP?

Brian M brayniac at gmail.com
Thu Jun 25 21:55:02 EDT 2015


Trying not to go offtopic. If there are specific lists for this type of
nuttery, contact me off list - would love to learn and discuss more.
That said - if you're going to test the impact on latency for interrupt
coalescing, I'd suggest using sockperf ping pong test:
https://github.com/mellanox/sockperf
Should reveal a bit more than a simple icmp ping test can. Use the --pps
flag to test a variety of packet rates. Should help show the effect of
coalescing.
- Brian

On Thu, Jun 25, 2015 at 13:40 Hal Murray <hmurray at megapathdsl.net> wrote:

>
> I know next-to-nothing about Windows.
>
> Serial ports are pretty standard.  I'd get the cheapest card.  I'd probably
> pay a bit more for a second port.  It might be handy tomorrow.
>
> One difference between chips is the depth of the FIFO.
>
> PCI card now come in two heights.  Make sure you get the right one.  The
> short ones don't have room for a second connector.  (Some cards come with
> two
> face plates.  You can swap in/out the other one if you can use a
> screwdriver.)
>
>
> The other thing to keep an eye on is interrupts from the Gigabit ethernet.
> With a lot of short packets, you can get in trouble spending all your CPU
> time in the interrupt handler.  Some hardware is setup to batch interrupts.
> The idea is to delay an interrupt for a while in hopes that more packets
> will
> arrive and get processed as a batch.  You may want to turn that off.  It's
> a
> tradeoff between latency and CPU usage.  You may be able to measure it with
> something like ping.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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