lkml.org 
[lkml]   [2008]   [Jan]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: e1000 full-duplex TCP performance well below wire speed
Hi Stephen,

>>>> Indeed, we are not asking to see 1000 Mb/s. We'd be happy to see 900
>>>> Mb/s.
>>>>
>>>> Netperf is trasmitting a large buffer in MTU-sized packets (min 1500
>>>> bytes). Since the acks are only about 60 bytes in size, they should be
>>>> around 4% of the total traffic. Hence we would not expect to see more
>>>> than 960 Mb/s.
>>
>>> Don't forget the network overhead: http://sd.wareonearth.com/~phil/net/overhead/
>>> Max TCP Payload data rates over ethernet:
>>> (1500-40)/(38+1500) = 94.9285 % IPv4, minimal headers
>>> (1500-52)/(38+1500) = 94.1482 % IPv4, TCP timestamps
>>
>> Yes. If you look further down the page, you will see that with jumbo
>> frames (which we have also tried) on Gb/s ethernet the maximum throughput
>> is:
>>
>> (9000-20-20-12)/(9000+14+4+7+1+12)*1000000000/1000000 = 990.042 Mbps
>>
>> We are very far from this number -- averaging perhaps 600 or 700 Mbps.

> That is the upper bound of performance on a standard PCI bus (32 bit).
> To go higher you need PCI-X or PCI-Express. Also make sure you are really
> getting 64-bit PCI, because I have seen some e1000 PCI-X boards that
> are only 32bit.

The motherboard NIC is in a PCI-e x1 slot. This has a maximum speed of
250 MB/s (2 Gb/s) in each direction. It should be a factor of 2 more
interface speed than is needed.

Cheers,
Bruce


\
 
 \ /
  Last update: 2008-01-31 00:25    [W:1.130 / U:0.652 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site