On Wed, Feb 17, 2016 at 7:38 PM, Jeff Kirsher
<[email protected]> wrote:
> From: Mitch Williams <[email protected]>
>
> Mr. Spock would certainly raise an eyebrow to see us using bitwise
> operators, when we should clearly be relying on logic. Fascinating.
>
> Change-ID: Ie338010c016f93e9faa2002c07c90b15134b7477
> Signed-off-by: Mitch Williams <[email protected]>
> Tested-by: Andrew Bowers <[email protected]>
> Signed-off-by: Jeff Kirsher <[email protected]>
NAK
The bitwise operator lets us at least make a pass through all rings.
With this new code you stop as soon as one ring has not completed
cleaning.
> ---
> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 5 +++--
> drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 5 +++--
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index 1abef01..0ffa9a8 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -1996,7 +1996,8 @@ int i40e_napi_poll(struct napi_struct *napi, int budget)
> * budget and be more aggressive about cleaning up the Tx descriptors.
> */
> i40e_for_each_ring(ring, q_vector->tx) {
> - clean_complete &= i40e_clean_tx_irq(ring, vsi->work_limit);
> + clean_complete = clean_complete &&
> + i40e_clean_tx_irq(ring, vsi->work_limit);
> arm_wb = arm_wb || ring->arm_wb;
> ring->arm_wb = false;
> }
For example here. You now will not call i40e_clean_tx_irq if
clean_complete is false.
> @@ -2020,7 +2021,7 @@ int i40e_napi_poll(struct napi_struct *napi, int budget)
>
> work_done += cleaned;
> /* if we didn't clean as many as budgeted, we must be done */
> - clean_complete &= (budget_per_ring != cleaned);
> + clean_complete = clean_complete && (budget_per_ring >
> cleaned);
> }
>
> /* If work not completed, return budget and polling will return */
This code is now slower after this change.
