RE: [Xen-users] Bad TCP accept performance

["Russ Purinton" <rpurinton@xxxxxxxxxxxxxxxxxxxxxxx>]

Could there be a difference in loopback behavior with linux vs windows?  I have 
noticed that TCP connections are established by apache in about 0.6ms and IIS 
takes about 75ms to accept them most times.

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Tian, Kevin
Sent: Wednesday, May 25, 2011 10:55 PM
To: Russ Purinton; Pasi Kärkkäinen
Cc: Carl Byström; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] Bad TCP accept performance

> From: Russ Purinton
> Sent: Wednesday, May 25, 2011 11:49 PM
> 
> I thought that even 127.0.0.0/8 traffic still went thru the NIC to loop.  I 
> can't
> seem to find anything on the net supporting this one way or the other, though
> I've seen multiple posts about pinging 127.0.0.1 to test and verify the NIC 
> card
> and drivers working properly.  Not sure what this means.
> 
> Also, if it doesn't pass to the NIC, the NIC then the question arises how the 
> IP
> and TCP checksums are being applied if offloading is enabled and it doesn't 
> pass
> thru the NIC.
> 
> I had thought that on a physical host, the loopback ping would hit the network
> card.  I'm guessing with a virtual host, the loopback ping would only hit the

loopback driver simply queues the tx packet back to rx queue, and there's 
nothing
to do with underlying NIC. 

Thanks
Kevin

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