| Message ID | 20180829163021.70ce99ab@xhacker.debian |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | net: mvneta: some bug fix and trivial improvement | expand |
Hi Jisheng, On mer., août 29 2018, Jisheng Zhang <Jisheng.Zhang@synaptics.com> wrote: > 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. This improvement should go to net-next. Besides this patch looks nice: Reviewed-by: Gregory CLEMENT <gregory.clement@bootlin.com> Thanks, Gregory > > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com> > --- > drivers/net/ethernet/marvell/mvneta.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c > index 7d98f7828a30..62e81e267e13 100644 > --- a/drivers/net/ethernet/marvell/mvneta.c > +++ b/drivers/net/ethernet/marvell/mvneta.c > @@ -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); > -- > 2.18.0 >
diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index 7d98f7828a30..62e81e267e13 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -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);
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> --- drivers/net/ethernet/marvell/mvneta.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)