On Tue, Dec 11 2018, NeilBrown wrote: > > I got your patch working on 4.20-rc5 and did a performance comparison. > With the staging driver (using iperf3) I get > 220 MBit/sec in > 680 MBit/sec out > > with the patched mainline driver I get > 190 MBit/sec in > 93 MBit/sec out > > (numbers are a bit rubbery, but within 10%) > > I haven't looked into why this might be, but thought I would mention it. > > Strangely when I test with scp, I get about 10MB/sec in both directions > with both drivers. Maybe the CPU limits encryption speed. > > I have a 4.4-based kernel where I get 940MBit/sec both ways - using a > precursor of the current staging driver.
Just FYI, I've been looking further into this, and I don't think the problem is (entirely) related to the driver. In my 4.4 kernel, the build_skb() call in (the equivalent of) mtk_poll_rx() takes about 1.2usec and the call to napi_gro_receive() takes about 3usec. In my 4.20 kernel, these calls take about 30 and 24 usec respectively. This easily explains the slowdown. I don't yet know why, and won't have time to look for a few days. I haven't looked into how this affects the drivers/net/ethernet/mediatek driver in 4.20. If anyone has ideas about why these might be so slow, I'd love to hear them. Thanks, NeilBrown
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