ix(intel) vs mlxen(mellanox) 10Gb performance

[Slawa Olhovchenkov]

On Mon, Aug 17, 2015 at 05:44:37PM +0200, Alban Hertroys wrote:

> On 17 August 2015 at 13:54, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:
> > On Mon, Aug 17, 2015 at 01:49:27PM +0200, Alban Hertroys wrote:
> >
> >> On 17 August 2015 at 13:39, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:
> >>
> >> > In any case, for 10Gb expect about 1200MGB/s.
> >>
> >> Your usage of units is confusing. Above you claim you expect 1200
> >
> > I am use as topic starter and expect MeGaBytes per second
> 
> That's a highly unusual way of writing MB/s.

I am know. This is do not care for me.

> There are standards for unit prefixes: k means kilo, M means Mega, G
> means Giga, etc. See:
> https://en.wikipedia.org/wiki/International_System_of_Units#Prefixes
> 
> >> million gigabytes per second, or 1.2 * 10^18 Bytes/s. I don't think
> >> any known network interface can do that, including highly experimental
> >> ones.
> >>
> >> I suspect you intended to claim that you expect 1.2GB/s (Gigabytes per
> >> second) over that 10Gb/s (Gigabits per second) network.
> >> That's still on the high side of what's possible. On TCP/IP there is
> >> some TCP overhead, so 1.0 GB/s is probably more realistic.
> >
> > TCP give 5-7% overhead (include retrasmits).
> > 10^9/8*0.97 = 1.2125
> 
> In information science, Bytes are counted in multiples of 2, not 10. A
> kb is 1024 bits or 2^10 b. So 10 Gb is 10 * 2^30 bits.

Interface speeds counted in multile of 10.
10Mbit ethernet have speed 10^7 bit/s.
64Kbit ISDN have speed 64000, not 65536.

> It's also not unusual to be more specific about that 2-base and use
> kib, Mib and Gib instead.
> 
> Apparently you didn't know that...
> 
> Also, if you take 5% off, you are left with (0.95 * 10 * 2^30) / 8 =
> 1.1875 B/s, not 0.97 * ... Your calculations were a bit optimistic.

May bug.
10^10/8*0.93 = 1162500000 = 1162.5

> Now I have to admit I'm used to use a factor of 10 to convert from b/s
> to B/s (that's 20%!), but that's probably no longer correct, what with
> jumbo frames and all.

Ok, may be topic started use software metered speed with MGBs as
1048576 per second. 1162500000/1048576 = 1108.64