[openib-general] Re: [PATCH] TX/RX_RING_SIZE as loadable parameters

[Michael S. Tsirkin]

Quoting r. Shirley Ma <xma at us.ibm.com>:
> Subject: [PATCH] TX/RX_RING_SIZE as loadable parameters
> 
> 
> Hello Roland,
> 
> The default TX_RING_SIZE is 64, RX_RING_SIZE is 128 in IPoIB, which are not optimized for all IB device drivers. We saw numerous retransmissions in our MPI stress test cluster environment. I've changed these two parameters as loadable. We even got 6 times better performance test results with much bigger TX/RX_RING_SIZE, and no more retransmissions. I think it's more reasonable to allow these parameters to be set during module load.
> 
> Here is the patch for review.
> 
> Sign-off-by: Shirley Ma <xma at us.ibm.com>

These parameters must be a power of 2, and at least 2, otherwise things
break. I'd suggest making these a log and multiplying the result by 2,
to exclude the possibility of user error.

The final tx_ring_size and rx_ring_size after doing all the math probably
should go into priv structure, to improve cache locality.

-- 
Michael S. Tsirkin
Staff Engineer, Mellanox Technologies