8.2-RELEASE and stable/8 have the same problem. Ping RTT triples
when MSIX is disabled.

On 10/3/2011 11:50 AM, Jack Vogel wrote:
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 <[email protected] 
<mailto:[email protected]>> 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 <[email protected] 
<mailto:[email protected]>> 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 <http://192.168.1.83>: icmp_seq=0 ttl=64 
time=0.055 ms
        64 bytes from 192.168.1.83 <http://192.168.1.83>: icmp_seq=1 ttl=64 
time=0.076 ms
        64 bytes from 192.168.1.83 <http://192.168.1.83>: icmp_seq=2 ttl=64 
time=0.066 ms
        64 bytes from 192.168.1.83 <http://192.168.1.83>: icmp_seq=3 ttl=64 
time=0.051 ms
        64 bytes from 192.168.1.83 <http://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 <http://192.168.1.83>: icmp_seq=0 ttl=64 
time=0.180 ms
        64 bytes from 192.168.1.83 <http://192.168.1.83>: icmp_seq=1 ttl=64 
time=0.164 ms
        64 bytes from 192.168.1.83 <http://192.168.1.83>: icmp_seq=2 ttl=64 
time=0.169 ms
        64 bytes from 192.168.1.83 <http://192.168.1.83>: icmp_seq=3 ttl=64 
time=0.172 ms
        64 bytes from 192.168.1.83 <http://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?









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