em(4) high latency w/o msix

[Jack Vogel]

Can you try the driver in 8.2 and possibly stable/8 to see the behavior
there.

And, just curious, why are you disabling MSIX?

Jack


On Mon, Oct 3, 2011 at 12:51 AM, Hooman Fazaeli <fazaeli at sepehrs.com> wrote:

> **
> Hi Jack
>
> The hardware is a PCIe network appliance with 3 port modules. The ports I
> have
> used in the test are 82574L residing on a 4 port module. Anyway, as I noted
> in last mail, the stock 7.3-RELEASE driver does not expose this problem on
> the same hardware.
>
>
> On 10/2/2011 7:38 PM, Jack Vogel wrote:
>
> On what hardware?
>
> Jack
>
>
> On Sun, Oct 2, 2011 at 6:42 AM, Hooman Fazaeli <fazaeli at sepehrs.com>wrote:
>
>>
>> Latest em(4) driver from HEAD seems to have high latency
>> when MSIX is disabled.
>>
>> With MSIX enabled (hw.em.enable_msix=1):
>>
>> # ping -c5 192.168.1.83
>> PING 192.168.1.83 (192.168.1.83): 56 data bytes
>> 64 bytes from 192.168.1.83: icmp_seq=0 ttl=64 time=0.055 ms
>> 64 bytes from 192.168.1.83: icmp_seq=1 ttl=64 time=0.076 ms
>> 64 bytes from 192.168.1.83: icmp_seq=2 ttl=64 time=0.066 ms
>> 64 bytes from 192.168.1.83: icmp_seq=3 ttl=64 time=0.051 ms
>> 64 bytes from 192.168.1.83: icmp_seq=4 ttl=64 time=0.063 ms
>>
>> --- 192.168.1.83 ping statistics ---
>> 5 packets transmitted, 5 packets received, 0.0% packet loss
>> round-trip min/avg/max/stddev = 0.051/0.062/0.076/0.009 ms
>>
>> With MSIX disabled:
>>
>> # ping -c5 192.168.1.83
>> PING 192.168.1.83 (192.168.1.83): 56 data bytes
>> 64 bytes from 192.168.1.83: icmp_seq=0 ttl=64 time=0.180 ms
>> 64 bytes from 192.168.1.83: icmp_seq=1 ttl=64 time=0.164 ms
>> 64 bytes from 192.168.1.83: icmp_seq=2 ttl=64 time=0.169 ms
>> 64 bytes from 192.168.1.83: icmp_seq=3 ttl=64 time=0.172 ms
>> 64 bytes from 192.168.1.83: icmp_seq=4 ttl=64 time=0.167 ms
>>
>> --- 192.168.1.83 ping statistics ---
>> 5 packets transmitted, 5 packets received, 0.0% packet loss
>> round-trip min/avg/max/stddev = 0.164/0.170/0.180/0.005 ms
>>
>> As you see, w/o MSIX, RTT increases by a factor of 3.
>>
>> I also tested the following drivers:
>>    - igb(4) from HEAD: OK.
>>    - Stock 7.3-RELEASE: OK.
>>    - Stock 7.4-RELEASE: problem exist.
>>
>> Any ideas?
>>
>>
>>
>>
>>
>