[ewg] RE: [ofa-general] [PATCH] ib_send_bw -b can hang due to too few CQ entries

[Ralph Campbell]

On Thu, 2009-08-06 at 14:56 -0700, Sean Hefty wrote:
> >Sure. Just above the call to ibv_create_cq(), ctx->rx_depth is set to
> >	ctx->rx_depth = rx_depth + tx_depth
> >but the rest of the code does ibv_post_send() and ibv_post_recv()
> >based on ctx->tx_depth and ctx->rx_depth which means the CQ needs
> >to be ctx->tx_depth + ctx->rx_depth big.
> 
> If the tx_depth is the same on both sides, why would there ever be more than the
> initial tx_depth and rx_depth completions on the CQ?  How many receive
> completions can there be on the CQ, and what throttles the sender? 
> 
> - Sean

Remember that this fix only affects the bi-directional test.
Both client and sever are going to post ctx->rx_depth receives
and ctx->tx_depth sends and then check for completions.
It won't post more sends or receives until the completions are
seen.