Re: [PATCH 3/3 v2] net/macb: Try to optimize struct macb layout

Ben Hutchings
2012-12-17T13:52:33Z

On Mon, 2012-12-17 at 14:01 +0100, Nicolas Ferre wrote:
> From: Havard Skinnemoen <havard@skinnemoen.net>
>
> Move TX-related fields to the top of the struct so that they end up on
> the same cache line. Move the NAPI struct below that since it is used
> from the interrupt handler. RX-related fields go below those.

> Move the spinlock before regs since they are usually used together.
>
> Signed-off-by: Havard Skinnemoen <havard@skinnemoen.net>
> [nicolas.ferre@atmel.com: adapt to newer kernel]
> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> ---
> drivers/net/ethernet/cadence/macb.h | 25 +++++++++++++------------
> 1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> index cef146f..aeeb729 100644
> --- a/drivers/net/ethernet/cadence/macb.h
> +++ b/drivers/net/ethernet/cadence/macb.h
> @@ -548,38 +548,39 @@ struct macb_or_gem_ops {
> };
>
> struct macb {
> + spinlock_t lock;
> void __iomem *regs;
>
> + unsigned int tx_head;
> + unsigned int tx_tail;
> + struct macb_dma_desc *tx_ring;
> + struct macb_tx_skb *tx_skb;
> + dma_addr_t tx_ring_dma;
> + struct work_struct tx_error_task;
> +
> + struct napi_struct napi;
[...]

If this driver may be used on SMP systems them 'napi' should be declared
with the suffix ___cacheline_aligned_in_smp.

Ben.

--
Ben Hutchings, Staff Engineer, Solarflare
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