Re: em(4) high latency w/o msix
- From: Jack Vogel <jfvogel@xxxxxxxxx>
- Date: Sun, 2 Oct 2011 09:08:08 -0700
On what hardware?
Jack
On Sun, Oct 2, 2011 at 6:42 AM, Hooman Fazaeli <fazaeli@xxxxxxxxxxx> 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?
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