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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org (open list) Subject: [PATCH 06/10] net: emac: batch stats, eliminate modulo, tighten barrier in RX poll Date: Mon, 29 Jun 2026 21:16:30 -0700 Message-ID: <20260630041634.284127-7-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260630041634.284127-1-rosenp@gmail.com> References: <20260630041634.284127-1-rosenp@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Three small hot-path changes in emac_poll_rx(): - Batch per-packet 64-bit stat updates into local accumulators and write dev->stats once after the poll loop, avoiding expensive load-linked/store-conditional sequences on 32-bit PPC for every received packet. - Replace slot = (slot + 1) % NUM_RX_BUFF with a simple if (++slot == NUM_RX_BUFF) branch, avoiding a div/mul by a non-power-of-2 constant. - Use dma_rmb() instead of mb() when ordering the ctrl vs. data_len read of the coherent RX descriptor. The device writes the descriptor fields in-order and clears MAL_RX_CTRL_EMPTY last; a read barrier is sufficient. Assisted-by: opencode:big-pickle Signed-off-by: Rosen Penev --- drivers/net/ethernet/ibm/emac/core.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c index 5e7b85d28bde..ced9690cddc3 100644 --- a/drivers/net/ethernet/ibm/emac/core.c +++ b/drivers/net/ethernet/ibm/emac/core.c @@ -1741,6 +1741,7 @@ static int emac_poll_rx(void *param, int budget) { struct emac_instance *dev = param; int slot = dev->rx_slot, received = 0; + u64 packets = 0, bytes = 0; DBG2(dev, "poll_rx(%d)" NL, budget); @@ -1797,10 +1798,11 @@ static int emac_poll_rx(void *param, int budget) napi_gro_receive(&dev->mal->napi, skb); next: - ++dev->stats.rx_packets; + ++packets; skip: - dev->stats.rx_bytes += len; - slot = (slot + 1) % NUM_RX_BUFF; + bytes += len; + if (++slot == NUM_RX_BUFF) + slot = 0; --budget; ++received; continue; @@ -1864,6 +1866,9 @@ static int emac_poll_rx(void *param, int budget) emac_rx_enable(dev); dev->rx_slot = 0; } + + dev->stats.rx_packets += packets; + dev->stats.rx_bytes += bytes; return received; } -- 2.54.0