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[23.128.96.18]) by mx.google.com with ESMTP id bc26si3501391edb.508.2021.01.22.04.57.36; Fri, 22 Jan 2021 04:58:06 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="tMV/YSv1"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727301AbhAVM4I (ORCPT + 99 others); Fri, 22 Jan 2021 07:56:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726900AbhAVM4G (ORCPT ); Fri, 22 Jan 2021 07:56:06 -0500 Received: from mail-pl1-x631.google.com (mail-pl1-x631.google.com [IPv6:2607:f8b0:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDCE0C0613D6; Fri, 22 Jan 2021 04:55:25 -0800 (PST) Received: by mail-pl1-x631.google.com with SMTP id u11so3103377plg.13; Fri, 22 Jan 2021 04:55:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+hdkdzhBLRYgvWLyAgaaAF1+dexomSUfv4h9wGuekbc=; b=tMV/YSv1dbJYrEpAOaynp5dVr1c8ueO2IIrqtQcGDG9BWEx4DG5STuNJWMatx7zHi5 L9bilSa+SvFBsYb4wp9oZL6Zqq67IX3HCeXwB1NtZAdzF4SeZZzmKKlx2TeYuFXH869s NRZfa6DX/ywvSxXEZHOLqh5QDEQe3YO6rgRXHqJIUf+8h3LhPuv6tAl4Qbj+BQ5Xftwa PYc/1Qczo5z6+b4NCvnFcXoj5IcCPCiakSTJVTRzjry26TZASmlZ0aaH6tTiuAyqhe3n 2wV6DVJwEhd1zQzqmy8iqw1N6BPgXzhYDCsTdV7qMiXKNQ7ougUvYjFzbs6SaZyN77h/ hqaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+hdkdzhBLRYgvWLyAgaaAF1+dexomSUfv4h9wGuekbc=; b=Mr/dPJHM/z5ukssj6cVU6eXp4OLxt/9V8M+aXgUsrPm1ywxWOkSMB26e0c4/zwiCzZ CRFnGm6Tv4DitJ3f/YC3rgm3AKO0luSbCyTFjgf9iTkAC1D0HcqUT+BGKZKy5iVwi6wL 95AusTWRMLVc8IYv83szo4bzT2brwzlGR9MtAdIb9rbtd6dpkbcvEXdKiuGRWR0S7iCv e4g4gYUebDLdgzM9iH2EB033VzMqqJbdHfaBmw4c/iEsOq5OCdEbR6SqZcNjqCPvZHMv 4pV7aR12d+tijUwbQgh6vQZ4aTKyPfFp/YnyfmDTJgEZY9Yfm2B61UZkl5oKaFWzO+wI 0SDA== X-Gm-Message-State: AOAM530P1IGCNX3abI8PC/82iB6V62EoOYcUvLICRb/qiKmgSMRSe1Vb 297xXIlJUYXW4uVmrmrKJ6zOATG62y0sYbdq4/Q= X-Received: by 2002:a17:90a:14e2:: with SMTP id k89mr5085872pja.168.1611320125462; Fri, 22 Jan 2021 04:55:25 -0800 (PST) MIME-Version: 1.0 References: <340f1dfa40416dd966a56e08507daba82d633088.1611236588.git.xuanzhuo@linux.alibaba.com> <20210122114729.1758-1-alobakin@pm.me> <20210122115519.2183-1-alobakin@pm.me> <20210122123909.3603-1-alobakin@pm.me> In-Reply-To: <20210122123909.3603-1-alobakin@pm.me> From: Magnus Karlsson Date: Fri, 22 Jan 2021 13:55:14 +0100 Message-ID: Subject: Re: [PATCH bpf-next v3 3/3] xsk: build skb by page To: Alexander Lobakin Cc: Eric Dumazet , Xuan Zhuo , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Bjorn Topel , Magnus Karlsson , Jonathan Lemon , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , virtualization@lists.linux-foundation.org, bpf , Network Development , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 22, 2021 at 1:39 PM Alexander Lobakin wrote: > > From: Magnus Karlsson > Date: Fri, 22 Jan 2021 13:18:47 +0100 > > > On Fri, Jan 22, 2021 at 12:57 PM Alexander Lobakin wrote: > > > > > > From: Alexander Lobakin > > > Date: Fri, 22 Jan 2021 11:47:45 +0000 > > > > > > > From: Eric Dumazet > > > > Date: Thu, 21 Jan 2021 16:41:33 +0100 > > > > > > > > > On 1/21/21 2:47 PM, Xuan Zhuo wrote: > > > > > > This patch is used to construct skb based on page to save memory copy > > > > > > overhead. > > > > > > > > > > > > This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the > > > > > > network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to > > > > > > directly construct skb. If this feature is not supported, it is still > > > > > > necessary to copy data to construct skb. > > > > > > > > > > > > ---------------- Performance Testing ------------ > > > > > > > > > > > > The test environment is Aliyun ECS server. > > > > > > Test cmd: > > > > > > ``` > > > > > > xdpsock -i eth0 -t -S -s > > > > > > ``` > > > > > > > > > > > > Test result data: > > > > > > > > > > > > size 64 512 1024 1500 > > > > > > copy 1916747 1775988 1600203 1440054 > > > > > > page 1974058 1953655 1945463 1904478 > > > > > > percent 3.0% 10.0% 21.58% 32.3% > > > > > > > > > > > > Signed-off-by: Xuan Zhuo > > > > > > Reviewed-by: Dust Li > > > > > > --- > > > > > > net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++---------- > > > > > > 1 file changed, 86 insertions(+), 18 deletions(-) > > > > > > > > > > > > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c > > > > > > index 4a83117..38af7f1 100644 > > > > > > --- a/net/xdp/xsk.c > > > > > > +++ b/net/xdp/xsk.c > > > > > > @@ -430,6 +430,87 @@ static void xsk_destruct_skb(struct sk_buff *skb) > > > > > > sock_wfree(skb); > > > > > > } > > > > > > > > > > > > +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, > > > > > > + struct xdp_desc *desc) > > > > > > +{ > > > > > > + u32 len, offset, copy, copied; > > > > > > + struct sk_buff *skb; > > > > > > + struct page *page; > > > > > > + void *buffer; > > > > > > + int err, i; > > > > > > + u64 addr; > > > > > > + > > > > > > + skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err); > > > > > > + if (unlikely(!skb)) > > > > > > + return ERR_PTR(err); > > > > > > + > > > > > > + addr = desc->addr; > > > > > > + len = desc->len; > > > > > > + > > > > > > + buffer = xsk_buff_raw_get_data(xs->pool, addr); > > > > > > + offset = offset_in_page(buffer); > > > > > > + addr = buffer - xs->pool->addrs; > > > > > > + > > > > > > + for (copied = 0, i = 0; copied < len; i++) { > > > > > > + page = xs->pool->umem->pgs[addr >> PAGE_SHIFT]; > > > > > > + > > > > > > + get_page(page); > > > > > > + > > > > > > + copy = min_t(u32, PAGE_SIZE - offset, len - copied); > > > > > > + > > > > > > + skb_fill_page_desc(skb, i, page, offset, copy); > > > > > > + > > > > > > + copied += copy; > > > > > > + addr += copy; > > > > > > + offset = 0; > > > > > > + } > > > > > > + > > > > > > + skb->len += len; > > > > > > + skb->data_len += len; > > > > > > > > > > > + skb->truesize += len; > > > > > > > > > > This is not the truesize, unfortunately. > > > > > > > > > > We need to account for the number of pages, not number of bytes. > > > > > > > > The easiest solution is: > > > > > > > > skb->truesize += PAGE_SIZE * i; > > > > > > > > i would be equal to skb_shinfo(skb)->nr_frags after exiting the loop. > > > > > > Oops, pls ignore this. I forgot that XSK buffers are not > > > "one per page". > > > We need to count the number of pages manually and then do > > > > > > skb->truesize += PAGE_SIZE * npages; > > > > > > Right. > > > > There are two possible packet buffer (chunks) sizes in a umem, 2K and > > 4K on a system with a PAGE_SIZE of 4K. If I remember correctly, and > > please correct me if wrong, truesize is used for memory accounting. > > But in this code, no kernel memory has been allocated (apart from the > > skb). The page is just a part of the umem that has been already > > allocated beforehand and by user-space in this case. So what should > > truesize be in this case? Do we add 0, chunk_size * i, or the > > complicated case of counting exactly how many 4K pages that are used > > when the chunk_size is 2K, as two chunks could occupy the same page, > > or just the upper bound of PAGE_SIZE * i that is likely a good > > approximation in most cases? Just note that there might be other uses > > of truesize that I am unaware of that could impact this choice. > > Truesize is "what amount of memory does this skb occupy with all its > fragments, linear space and struct sk_buff itself". The closest it > will be to the actual value, the better. > In this case, I think adding of chunk_size * i would be enough. Sounds like a good approximation to me. > (PAGE_SIZE * i can be overwhelming when chunk_size is 2K, especially > for setups with PAGE_SIZE > SZ_4K) You are right. That would be quite horrible on a system with a page size of 64K. > > > > > > + > > > > > > + refcount_add(len, &xs->sk.sk_wmem_alloc); > > > > > > + > > > > > > + return skb; > > > > > > +} > > > > > > + > > > > > > > > Al > > > > > > Thanks, > > > Al > > Al >