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SubjectRe: [PATCH 2/4] macvlan: cleanup rx statistics
Arnd Bergmann a écrit :
> We have very similar code for rx statistics in
> two places in the macvlan driver, with a third
> one being added in the next patch.
>
> Consolidate them into one function to improve
> overall readability of the driver.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/net/macvlan.c | 63 +++++++++++++++++++++++++-----------------------
> 1 files changed, 33 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index ae2b5c7..a0dea23 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -116,42 +116,53 @@ static int macvlan_addr_busy(const struct macvlan_port *port,
> return 0;
> }
>
> +static inline void macvlan_count_rx(const struct macvlan_dev *vlan, int length,
> + int success, int multicast)

success and multicast should be declared as bool

> +{
> + struct macvlan_rx_stats *rx_stats;
> +
> + rx_stats = per_cpu_ptr(vlan->rx_stats, smp_processor_id());
> + rx_stats->rx_packets += success != 0;
> + rx_stats->rx_bytes += success ? length : 0;
> + rx_stats->multicast += success && multicast;
> + rx_stats->rx_errors += !success;
> +}
> +

I find following more readable, it probably generates more branches,
but avoid dirtying rx_errors if it is in another cache line.

if (likely(success)) {
rx_stats->rx_packets++;
rx_stats->rx_bytes += length;
if (multicast)
rx_stats->multicast++;
} else {
rx_stats->rx_errors++;
}


> - rx_stats = per_cpu_ptr(vlan->rx_stats, smp_processor_id());
> skb = skb_share_check(skb, GFP_ATOMIC);
> - if (skb == NULL) {
> - rx_stats->rx_errors++;
> - return NULL;
> - }
> -
> - rx_stats->rx_bytes += skb->len + ETH_HLEN;
> - rx_stats->rx_packets++;
> + macvlan_count_rx(vlan, skb->len + ETH_HLEN, likely(skb != NULL), 0);

its not _likely_ that skb != NULL, its a fact :)

-> macvlan_count_rx(vlan, skb->len + ETH_HLEN, true, false);

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