Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Poor performance with PCIe and DMA on Linux

Hello all, I built a evaluation system on the Arria II dev board that transports two similar datastreams to a linux host so that each stream can be read from a different device file. The s...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Hello again,

I did more tests.

I doubled the datawidth from 32 bit to 64 bit. The fifos write doublewords so the throughput is doubled in theory, because the pcie-tx-port ist 64 bit wide.

In fact the throughput isn't better now.

If I increase the DMA-block-length, the whole card freezes. The PCIe-interface sets waitrequest and stays in an that state. The card does not react to any command until I reset it. If I put debugging messages into my driver's code, the block length can be bigger, because it takes time until the next dma-request.

This issue occured with singleword transfers, too.

Does anybody has an idea?

Regards,

Frederik