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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72d405485b7sm9320991b3a.2.2025.01.15.09.27.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2025 09:27:56 -0800 (PST) Date: Wed, 15 Jan 2025 09:27:53 -0800 From: Joe Damato To: Furong Xu <0x1207@gmail.com> Cc: netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Alexander Lobakin , Andrew Lunn , "David S. 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: Mail-Followup-To: Joe Damato , Furong Xu <0x1207@gmail.com>, netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Alexander Lobakin , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Coquelin , xfr@outlook.com References: <668cfa117e41a0f1325593c94f6bb739c3bb38da.1736777576.git.0x1207@gmail.com> <20250115103358.00005b57@gmail.com> 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-Disposition: inline In-Reply-To: <20250115103358.00005b57@gmail.com> On Wed, Jan 15, 2025 at 10:33:58AM +0800, Furong Xu wrote: > 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.q No worries. For what it's worth, it looks like there are a few other instances in this driver where net_prefetch or net_prefetchw can be used instead. That might be better as a followup / cleanup and separate from this series though. Just thought I'd mention it as you have a way to test the improvements and I, unfortunately, do not have one of these devices.