From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 95760C4332F for ; Thu, 24 Nov 2022 17:55:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=EfNjZb+TJWkR+zcujbZyexI/avzbZZh0Njte6oa+JWo=; b=N0nSeU1nfykrwl XeN7zifdHOu3PjmemzvA7AVs/KYJlCT/XGbt43x4pH4T1MgldVA/q6XNV1JdOxJZdEdBaQAY3tqF7 m+8w3sdZBjEL+8iDbfTYmjRXzTwLf4YROWGjqH9qy5njumC62auAnKqcQh6JfOwGknimYw/qhzkS4 QtjoKaVXyGBKTzyonxDnbLZT6pjldoth8yoMXhgrHcV8CtdiK5J76kKI/KPWwQQiX2usJBxOUPQwJ mZP/PQgfnSIcwgbEhPrPkyjIq8va/ioZfTPUpY9rkEQlT28QHHr/iNSxDa01mvjTXQpQfCvX62Ke9 37sldw9/K10jW5k5wNvg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oyGQb-00Afjk-Eb; Thu, 24 Nov 2022 17:54:26 +0000 Received: from mga12.intel.com ([192.55.52.136]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oyGQX-00Affz-IR; Thu, 24 Nov 2022 17:54:22 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1669312461; x=1700848461; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=sXnKN/YXOdlrt4gQi4aLdKbmQKzlc0Sj2MoBA1aMjMg=; b=XgHmkOrU0BvGUO7yvdQH+OlN3koG8DXmLqWeDFQT+dWu6RKykFwpiGAL iLjsuQJjRbYxxcQJvFFGnIPRNFJf6dV/Y+6qg0n4PM4PwP5IMExjhrF1u qihua1+a2femigS1Gpi4G8Wjz/458p44QDM3eyJfQGeP3kYRsD2SZj24/ f4TH5ZIMV8CaRR62PUlqIlXj7Yo2tUTynQ7xvqEbdL8eLiOrBm9W9xGpa HFuE98ajwUIczjTDcT+Wt+zwVF98MuJHTFZ5xlGF+Cz28jdOvBUa9C9+w n9Go36VFjYMbHG3gl5XPc9ny+O+/LZ5oicplHhq/wD9AcnV4cxGqflvVC Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10541"; a="294049570" X-IronPort-AV: E=Sophos;i="5.96,190,1665471600"; d="scan'208";a="294049570" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Nov 2022 09:54:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10541"; a="767146960" X-IronPort-AV: E=Sophos;i="5.96,190,1665471600"; d="scan'208";a="767146960" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by orsmga004.jf.intel.com with ESMTP; 24 Nov 2022 09:54:15 -0800 Received: from newjersey.igk.intel.com (newjersey.igk.intel.com [10.102.20.203]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id 2AOHsDbM003592; Thu, 24 Nov 2022 17:54:13 GMT From: Alexander Lobakin To: Felix Fietkau Cc: Alexander Lobakin , netdev@vger.kernel.org, John Crispin , Sean Wang , Mark Lee , Lorenzo Bianconi , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Matthias Brugger , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/5] net: ethernet: mtk_eth_soc: work around issue with sending small fragments Date: Thu, 24 Nov 2022 18:54:10 +0100 Message-Id: <20221124175410.5684-1-alexandr.lobakin@intel.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123095754.36821-3-nbd@nbd.name> References: <20221123095754.36821-1-nbd@nbd.name> <20221123095754.36821-3-nbd@nbd.name> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221124_095421_675585_AE4FD94C X-CRM114-Status: GOOD ( 16.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Felix Fietkau Date: Wed, 23 Nov 2022 10:57:52 +0100 > When frames are sent with very small fragments, the DMA engine appears to > lock up and transmit attempts time out. Fix this by detecting the presence > of small fragments and use skb_gso_segment + skb_linearize to deal with > them Nit: all of your commit messages don't have a trailing dot (.), not sure if it's important, but my eye is missing it definitely :D skb_gso_segment() and skb_linearize() are slow as hell. I think you can do it differently. I guess only the first (head) and the last frag can be so small, right? So, if a frag from shinfo->frags is less than 16, get a new frag of the minimum acceptable size via netdev_alloc_frag(), copy the data to it and pad the rest with zeroes. Then increase skb->len and skb->data_len, skb_frag_unref() the current, "invalid" frag and replace the pointer to the new frag. I didn't miss anything I believe... Zero padding the tail is usual thing for NICs. skb frag substitution is less common, but should be legit. If skb_headlen() is less than 16, try doing pskb_may_pull() + __skb_pull() at first. The argument would be `16 - headlen`. If pskb_may_pull() returns false, then yeah, you have no choice other than segmenting and linearizing ._. > > Signed-off-by: Felix Fietkau > --- > drivers/net/ethernet/mediatek/mtk_eth_soc.c | 36 +++++++++++++++++++-- > 1 file changed, 34 insertions(+), 2 deletions(-) [...] > if (unlikely(atomic_read(&ring->free_count) <= ring->thresh)) > netif_tx_stop_all_queues(dev); > -- > 2.38.1 Thanks, Olek _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel