Arthur/David/Jeff,
Thanks for pointing that out. We will wait for any other comments
on our 12 patches. If there are no other, will send out a patch13
to include the mmiowb() change.

Thanks,
Ravi

-----Original Message-----
From: Arthur Kepner [mailto:akepner@sgi.com]
Sent: Friday, July 08, 2005 8:31 AM
To: Raghavendra Koushik
Cc: jgarzik@pobox.com; netdev@oss.sgi.com; netdev@vger.kernel.org;
ravinandan.arakali@neterion.com; leonid.grossman@neterion.com;
rapuru.sriram@neterion.com
Subject: RE: [PATCH 2.6.12.1 5/12] S2io: Performance improvements


On Thu, 7 Jul 2005, Raghavendra Koushik wrote:

....
On an Altix machine I believe the readq was necessary to flush 
the PIO writes. How long did you run the tests? I had seen
in long duration tests that an occasional write 
(TXDL control word and the address) would be missed and the xmit
Get's stuck.

The most recent tests I did used pktgen, and they ran for a total 
time of ~.5 hours (changing pkt_size every 30 seconds or so). The 
pktgen tests and other tests (like nttcp) have been run several times, 
so I've exercised the card for a total of several hours without 
any problems.

quoted

FWIW, I've done quite a few performance measurements with the patch 
I posted earlier, and it's worked well. For 1500 byte mtus throughput 
goes up by ~20%. Is even the mmiowb() unnecessary?

Was this on 2.4 kernel because I think the readq would not have a 
significant impact on 2.6 kernels due to TSO.
(with TSO on the number of packets that actually enter the 
Xmit routine would be reduced apprx 40 times).
.....

This was with a 2.6 kernel (with TSO on). PIO reads are pretty 
expensive on Altix, so eliminating them really helps us. 

For big mtus (>=4KBytes) the benefit of replacing the readq()
with mmiowb() in s2io_xmit() is negligible. 

--
Arthur