Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754511AbdHIQ4o (ORCPT ); Wed, 9 Aug 2017 12:56:44 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39824 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754361AbdHIQzT (ORCPT ); Wed, 9 Aug 2017 12:55:19 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Euan Kemp , Seth Forshee , "Michael S. Tsirkin" , "David S. Miller" Subject: [PATCH 4.12 101/106] virtio_net: fix truesize for mergeable buffers Date: Wed, 9 Aug 2017 09:53:25 -0700 Message-Id: <20170809164531.305997904@linuxfoundation.org> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170809164515.714288642@linuxfoundation.org> References: <20170809164515.714288642@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2365 Lines: 61 4.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Michael S. Tsirkin" [ Upstream commit 1daa8790d0280d2c719658e39bd59fce65efa909 ] Seth Forshee noticed a performance degradation with some workloads. This turns out to be due to packet drops. Euan Kemp noticed that this is because we drop all packets where length exceeds the truesize, but for some packets we add in extra memory without updating the truesize. This in turn was kept around unchanged from ab7db91705e95 ("virtio-net: auto-tune mergeable rx buffer size for improved performance"). That commit had an internal reason not to account for the extra space: not enough bits to do it. No longer true so let's account for the allocated length exactly. Many thanks to Seth Forshee for the report and bisecting and Euan Kemp for debugging the issue. Fixes: 680557cf79f8 ("virtio_net: rework mergeable buffer handling") Reported-by: Euan Kemp Tested-by: Euan Kemp Reported-by: Seth Forshee Tested-by: Seth Forshee Signed-off-by: Michael S. Tsirkin Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/virtio_net.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -889,21 +889,20 @@ static int add_recvbuf_mergeable(struct buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; buf += headroom; /* advance address leaving hole at front of pkt */ - ctx = (void *)(unsigned long)len; get_page(alloc_frag->page); alloc_frag->offset += len + headroom; hole = alloc_frag->size - alloc_frag->offset; if (hole < len + headroom) { /* To avoid internal fragmentation, if there is very likely not * enough space for another buffer, add the remaining space to - * the current buffer. This extra space is not included in - * the truesize stored in ctx. + * the current buffer. */ len += hole; alloc_frag->offset += hole; } sg_init_one(rq->sg, buf, len); + ctx = (void *)(unsigned long)len; err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp); if (err < 0) put_page(virt_to_head_page(buf));