From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [net-next.git 3/7] stmmac: review private structure fields Date: Wed, 03 Apr 2013 00:21:31 -0700 Message-ID: <1364973691.13853.7.camel@edumazet-glaptop> References: <1364967689-11155-1-git-send-email-peppe.cavallaro@st.com> <1364967689-11155-3-git-send-email-peppe.cavallaro@st.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Giuseppe CAVALLARO Return-path: Received: from mail-pa0-f42.google.com ([209.85.220.42]:42781 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760725Ab3DCHVd (ORCPT ); Wed, 3 Apr 2013 03:21:33 -0400 Received: by mail-pa0-f42.google.com with SMTP id kq13so749106pab.15 for ; Wed, 03 Apr 2013 00:21:33 -0700 (PDT) In-Reply-To: <1364967689-11155-3-git-send-email-peppe.cavallaro@st.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2013-04-03 at 07:41 +0200, Giuseppe CAVALLARO wrote: > recently many new supports have been added in the stmmac driver w/o taking care > about where each new field had to be placed inside the private structure for > guaranteeing the best cache usage. > This is what I wanted in the beginning, so this patch reorganizes all the fields > in order to keep adjacent fields for cache effect. > I have also tried to optimize them by using pahole. > > Signed-off-by: Giuseppe Cavallaro > --- > drivers/net/ethernet/stmicro/stmmac/stmmac.h | 70 +++++++++++++------------- > 1 files changed, 35 insertions(+), 35 deletions(-) > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h > index 75f997b..8aa28c5 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h > @@ -35,36 +35,45 @@ > > struct stmmac_priv { > /* Frequently used values are kept adjacent for cache effect */ > - struct dma_desc *dma_tx ____cacheline_aligned; /* Basic TX desc */ > - struct dma_extended_desc *dma_etx; /* Extended TX descriptor */ > - dma_addr_t dma_tx_phy; > - struct sk_buff **tx_skbuff; > - dma_addr_t *tx_skbuff_dma; > + struct dma_extended_desc *dma_etx; > + struct dma_desc *dma_tx ____cacheline_aligned_in_smp; > + struct sk_buff **tx_skbuff ____cacheline_aligned_in_smp; dma_tx & tx_skbuff are readonly, why put them in separate cache lines ? It seems there is an abuse of ____cacheline_aligned_in_smp in this driver (especially if this driver only runs on UP arch)