On Mon, Aug 10, 2020 at 4:47 AM Willy Tarreau <w...@1wt.eu> wrote:
>
> Doing testing on real hardware showed that retrieving the TSC on every
> call had a non negligible cost, causing a loss of 2.5% on the accept()
> rate and 4% on packet rate when using iptables -m statistics.
And by "real hardware" I assume you mean x86, with a fairly fast and
high-performance TSC for get_random_entropy().
Reading the TSC takes on the order of 20-50 cycles, iirc.
But it can actually be *much* more expensive. On non-x86, it can be an
IO cycle to external chips.
And on older hardware VM's in x86, it can be a vm exit etc, so
thousands of cycles. I hope nobody uses those VM's any more, but it
would be a reasonable test-case for some non-x86 implementations, so..
IOW, no. You guys are - once again - ignoring reality.
Linus
