I'll include this fix in the next patch that incorporates
any other review comments coming my way.. Thanks for pointing
it out.

-Koushik

-----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:

quoted

....
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

quoted

FWIW, I've done quite a few performance measurements with 

the patch 

quoted

quoted

I posted earlier, and it's worked well. For 1500 byte 

mtus throughput 

quoted

quoted

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