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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Coquelin , xfr@outlook.com Subject: Re: [PATCH net-next v2 3/3] net: stmmac: Optimize cache prefetch in RX path Message-ID: <20250115103358.00005b57@gmail.com> In-Reply-To: References: <668cfa117e41a0f1325593c94f6bb739c3bb38da.1736777576.git.0x1207@gmail.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 14 Jan 2025 15:31:05 -0800, Joe Damato wrote: > On Mon, Jan 13, 2025 at 10:20:31PM +0800, Furong Xu wrote: > > Current code prefetches cache lines for the received frame first, and > > then dma_sync_single_for_cpu() against this frame, this is wrong. > > Cache prefetch should be triggered after dma_sync_single_for_cpu(). > > > > This patch brings ~2.8% driver performance improvement in a TCP RX > > throughput test with iPerf tool on a single isolated Cortex-A65 CPU > > core, 2.84 Gbits/sec increased to 2.92 Gbits/sec. > > > > Signed-off-by: Furong Xu <0x1207@gmail.com> > > --- > > drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +---- > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > index ca340fd8c937..b60f2f27140c 100644 > > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > @@ -5500,10 +5500,6 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue) > > > > /* Buffer is good. Go on. */ > > > > - prefetch(page_address(buf->page) + buf->page_offset); > > - if (buf->sec_page) > > - prefetch(page_address(buf->sec_page)); > > - > > buf1_len = stmmac_rx_buf1_len(priv, p, status, len); > > len += buf1_len; > > buf2_len = stmmac_rx_buf2_len(priv, p, status, len); > > @@ -5525,6 +5521,7 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue) > > > > dma_sync_single_for_cpu(priv->device, buf->addr, > > buf1_len, dma_dir); > > + prefetch(page_address(buf->page) + buf->page_offset); > > Minor nit: I've seen in other drivers authors using net_prefetch. > Probably not worth a re-roll just for something this minor. After switch to net_prefetch(), I get another 4.5% throughput improvement :) Thanks! This definitely worth a v3 of this series. pw-bot: changes-requested