From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jisheng.Zhang@synaptics.com (Jisheng Zhang) Date: Wed, 29 Aug 2018 16:30:21 +0800 Subject: [PATCH 5/5] net: mvneta: reduce smp_processor_id() calling in mvneta_tx_done_gbe In-Reply-To: <20180829162456.2bd69796@xhacker.debian> References: <20180829162456.2bd69796@xhacker.debian> Message-ID: <20180829163021.70ce99ab@xhacker.debian> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 --- 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