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net: mvneta: reduce smp_processor_id() calling in mvneta_tx_done_gbe 

In the loop of mvneta_tx_done_gbe(), we call the smp_processor_id()
each time, move the call out of the loop to optimize the code a bit.

Before the patch, the loop looks like(under arm64):

        ldr     x1, [x29,#120]
        ...
        ldr     w24, [x1,#36]
        ...
        bl      0 <_raw_spin_lock>
        str     w24, [x27,#132]
        ...

After the patch, the loop looks like(under arm64):

        ...
        bl      0 <_raw_spin_lock>
        str     w23, [x28,#132]
        ...
where w23 is loaded so be ready before the loop.

>From another side, mvneta_tx_done_gbe() is called from mvneta_poll()
which is in non-preemptible context, so it's safe to call the
smp_processor_id() function once.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Reviewed-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Jisheng Zhang 2018-08-31 16:11:09 +08:00 committed by David S. Miller
parent 7772988ad6
commit bd9f1ee364
1 changed files with 2 additions and 1 deletions
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3
drivers/net/ethernet/marvell/mvneta.c
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@ -2507,12 +2507,13 @@ static void mvneta_tx_done_gbe(struct mvneta_port *pp, u32 cause_tx_done)
{
struct mvneta_tx_queue *txq;
struct netdev_queue *nq;
int cpu = smp_processor_id();
while (cause_tx_done) {
txq = mvneta_tx_done_policy(pp, cause_tx_done);
nq = netdev_get_tx_queue(pp->dev, txq->id);
__netif_tx_lock(nq, smp_processor_id());
__netif_tx_lock(nq, cpu);
if (txq->count)
mvneta_txq_done(pp, txq);