From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [net PATCH] atl1c: Fix misuse of netdev_alloc_skb in refilling rx ring Date: Sun, 28 Jul 2013 16:20:54 -0700 Message-ID: <1375053654.3669.58.camel@edumazet-glaptop> References: <87k3kbdcmy.fsf@canonical.com> <1374960610.3607.13.camel@deadeye.wl.decadent.org.uk> <1374969583.3669.23.camel@edumazet-glaptop> <20130727.200205.67471633133830510.davem@davemloft.net> <20130728104446.GB9876@neilslaptop.think-freely.org> <1375028154.3669.30.camel@edumazet-glaptop> <20130728185318.GA10795@neilslaptop.think-freely.org> <1375042972.2546.17.camel@deadeye.wl.decadent.org.uk> <1375052482.3669.54.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Neil Horman , David Miller , luis.henriques@canonical.com, netdev@vger.kernel.org, jcliburn@gmail.com, stable@vger.kernel.org To: Ben Hutchings Return-path: Received: from mail-pa0-f48.google.com ([209.85.220.48]:38415 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089Ab3G1XU4 (ORCPT ); Sun, 28 Jul 2013 19:20:56 -0400 In-Reply-To: <1375052482.3669.54.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Sun, 2013-07-28 at 16:01 -0700, Eric Dumazet wrote: > On Sun, 2013-07-28 at 21:22 +0100, Ben Hutchings wrote: > > > > > Since we know lengths > 4K work, perhaps it would be worth testing with > > the fragment cache size reduced to 16K? The driver would never > > previously have used RX buffers crossing 16K boundaries, except if SLOB > > was used (and that's an unlikely combination). > > Sure, please note the following maths : > > NET_SKB_PAD + 1536 + sizeof(struct skb_shared_info) = 1920 > > 16384/1920 = 8 > > 32768/1920 = 17 > > I don't think atl1c is used in any critical host (given it doesn't even > provide RX checksums and GRO ...), so I will provide a patch doing mere > page allocations. > Oh well, look at code around line 2530 * The atl1c chip can DMA to 64-bit addresses, but it uses a single * shared register for the high 32 bits, so only a single, aligned, * 4 GB physical address range can be used at a time. * * Supporting 64-bit DMA on this hardware is more trouble than it's * worth. It is far easier to limit to 32-bit DMA than update * various kernel subsystems to support the mechanics required by a * fixed-high-32-bit system. */ if ((pci_set_dma_mask(pdev, DMA_BIT_MASK(32)) != 0) || (pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(32)) != 0)) { dev_err(&pdev->dev, "No usable DMA configuration,aborting\n"); goto err_dma; } It looks like we have a winner ! This $@!? really needs DMA32 allocations. Currently only tested on TX patch, it needs same care on RX diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c index 786a874..e2ee962 100644 --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c @@ -1660,7 +1660,8 @@ static int atl1c_alloc_rx_buffer(struct atl1c_adapter *adapter) while (next_info->flags & ATL1C_BUFFER_FREE) { rfd_desc = ATL1C_RFD_DESC(rfd_ring, rfd_next_to_use); - skb = netdev_alloc_skb(adapter->netdev, adapter->rx_buffer_len); + skb = __netdev_alloc_skb(adapter->netdev, adapter->rx_buffer_len, + GFP_ATOMIC | GFP_DMA32); if (unlikely(!skb)) { if (netif_msg_rx_err(adapter)) dev_warn(&pdev->dev, "alloc rx buffer failed\n");