From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934072AbdBQNfa convert rfc822-to-8bit (ORCPT ); Fri, 17 Feb 2017 08:35:30 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:40338 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933545AbdBQNf3 (ORCPT ); Fri, 17 Feb 2017 08:35:29 -0500 From: Gregory CLEMENT To: Jisheng Zhang Cc: , , , , , Subject: Re: [PATCH net-next v2 1/2] net: mvneta: avoid getting status from rx_desc as much as possible References: <20170217100233.2325-1-jszhang@marvell.com> <20170217100233.2325-2-jszhang@marvell.com> Date: Fri, 17 Feb 2017 14:35:21 +0100 In-Reply-To: <20170217100233.2325-2-jszhang@marvell.com> (Jisheng Zhang's message of "Fri, 17 Feb 2017 18:02:32 +0800") Message-ID: <87k28paqjq.fsf@free-electrons.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jisheng, On ven., févr. 17 2017, Jisheng Zhang wrote: > In hot code path mvneta_rx_hwbm(), the rx_desc->status is read twice. > The rx_desc is allocated by dma_alloc_coherent, it's uncacheable if > the device isn't cache-coherent, reading from uncached memory is > fairly slow. So reuse the read out rx_status to avoid the second > reading from uncached memory. > > Signed-off-by: Jisheng Zhang > Suggested-by: Arnd Bergmann This one is OK and I didn't see a regression: Tested-by: Gregory CLEMENT Gregory > --- > drivers/net/ethernet/marvell/mvneta.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c > index 61dd4462411c..06df72b8da85 100644 > --- a/drivers/net/ethernet/marvell/mvneta.c > +++ b/drivers/net/ethernet/marvell/mvneta.c > @@ -313,8 +313,8 @@ > ((addr >= txq->tso_hdrs_phys) && \ > (addr < txq->tso_hdrs_phys + txq->size * TSO_HEADER_SIZE)) > > -#define MVNETA_RX_GET_BM_POOL_ID(rxd) \ > - (((rxd)->status & MVNETA_RXD_BM_POOL_MASK) >> MVNETA_RXD_BM_POOL_SHIFT) > +#define MVNETA_RX_GET_BM_POOL_ID(status) \ > + (((status) & MVNETA_RXD_BM_POOL_MASK) >> MVNETA_RXD_BM_POOL_SHIFT) > > struct mvneta_statistic { > unsigned short offset; > @@ -1900,7 +1900,7 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp, > for (i = 0; i < rx_done; i++) { > struct mvneta_rx_desc *rx_desc = > mvneta_rxq_next_desc_get(rxq); > - u8 pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc); > + u8 pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc->status); > struct mvneta_bm_pool *bm_pool; > > bm_pool = &pp->bm_priv->bm_pools[pool_id]; > @@ -2075,7 +2075,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo, > rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE); > data = (u8 *)(uintptr_t)rx_desc->buf_cookie; > phys_addr = rx_desc->buf_phys_addr; > - pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc); > + pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_status); > bm_pool = &pp->bm_priv->bm_pools[pool_id]; > > if (!mvneta_rxq_desc_is_first_last(rx_status) || > -- > 2.11.0 > -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com