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
> > 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.