Message-Id: <200507081816.j68IGIKP024269@guinness.s2io.com>
From: "Raghavendra Koushik" <raghavendra.koushik@neterion.com>
To: "'Arthur Kepner'" <akepner@sgi.com>
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
Date: Fri, 8 Jul 2005 11:16:14 -0700
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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:
> 
> > ....
> > 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.
> 
> > 
> > > 
> > > 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
>