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 X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C408FC388F9 for ; Sat, 21 Nov 2020 14:38:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41BB722201 for ; Sat, 21 Nov 2020 14:38:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ac060P5t" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727936AbgKUOiC (ORCPT ); Sat, 21 Nov 2020 09:38:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727922AbgKUOiB (ORCPT ); Sat, 21 Nov 2020 09:38:01 -0500 Received: from mail-wr1-x444.google.com (mail-wr1-x444.google.com [IPv6:2a00:1450:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BA185C0613CF; Sat, 21 Nov 2020 06:37:59 -0800 (PST) Received: by mail-wr1-x444.google.com with SMTP id p8so13872614wrx.5; Sat, 21 Nov 2020 06:37:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:autocrypt:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=uWjggj2LgaDrTK7OTDqfKMOswwqFU3ZQPnsfVGvdxbM=; b=Ac060P5tBTf+vUKMrW4iyigJdsXRU7ihwsUjBcObS3prY6E2sgL3MmPl/gSjHq+qD7 g9tBOKepZTy0NqLNaEVgB50p/1X++o8Ew6p2mtbGgHpaXXFwMVr5qm7Yz688rKYpgKRp 7bXmERniLFvOgNCYS0DlamsEFaZ7givkcIzVwXu6pPDttwXWCgi9llbpBwqfUfHfvRM5 Sn0FPDnbi6J8CTz6MTTq9PZ0NrejGoxQj+dwxB3RDH8U4cA/DJ4haHDAKlRV8tU1Fgos cSkCGYDsyFXMu5WVZxfH4KvBts4+VJGxbUcf8VaI55BHbfqlyq0MNIE7s/jxaAvYXiEi DCgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=uWjggj2LgaDrTK7OTDqfKMOswwqFU3ZQPnsfVGvdxbM=; b=aw4VY2aU3AqlwlFf8M3cFo8Nw8dXvd+Ht0Ehsp1Kjz4tuZKk4Gt0smex/Zdd4VAf3Q RdxpV40oMssrUYhKQ8cBRG1Qf8PoZ4ASi+TPWos67qbfdFJzLB42J9ktmjjVVbtSvonr ceE3fDbM4/gjz2ZY/pSJjJpPKGaL+WRrs0g3nlMN9MI9JTCIk5UCdL3gn5C6IvP3S/Qx Ux+thK/Cm4mraYrCBZlbXuJxpwbGEH15rNdvewmqDKn9YF8nD9YM3TBR/pEflp5x+H6F GRJM6bsgTpC41t73bLyl6+iN5/2QVg5sqR2WK7QECRlRFh8SLfM+gUvFSIyp7EdBqMm1 BKAQ== X-Gm-Message-State: AOAM532hMQVl3Wqq0sQmO3QGCd7VZ/42osnPwfI8lWPK3QGr5DtCvK9e rG0vaidsMkBwz1bp9l5KPOyIlyFoJ6c= X-Google-Smtp-Source: ABdhPJwS6khJVWhhtBIAjCngM3jmeEZzsBedBNdC0rBX3mI1ECByMZtHcijWO6PZvdF30OZ+SOMupg== X-Received: by 2002:adf:e512:: with SMTP id j18mr22941758wrm.390.1605969478130; Sat, 21 Nov 2020 06:37:58 -0800 (PST) Received: from [192.168.1.173] (host109-152-100-135.range109-152.btcentralplus.com. [109.152.100.135]) by smtp.gmail.com with ESMTPSA id i5sm9228795wrw.45.2020.11.21.06.37.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 21 Nov 2020 06:37:57 -0800 (PST) Subject: Re: [PATCH 00/29] RFC: iov_iter: Switch to using an ops table To: David Howells , Matthew Wilcox , Jens Axboe , Alexander Viro Cc: Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <4a277f64-e744-34cc-a4ec-16636f23b13a@gmail.com> Date: Sat, 21 Nov 2020 14:34:50 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 21/11/2020 14:13, David Howells wrote: > > Hi Pavel, Willy, Jens, Al, > > I had a go switching the iov_iter stuff away from using a type bitmask to > using an ops table to get rid of the if-if-if-if chains that are all over > the place. After I pushed it, someone pointed me at Pavel's two patches. > > I have another iterator class that I want to add - which would lengthen the > if-if-if-if chains. A lot of the time, there's a conditional clause at the > beginning of a function that just jumps off to a type-specific handler or > to reject the operation for that type. An ops table can just point to that > instead. > > As far as I can tell, there's no difference in performance in most cases, > though doing AFS-based kernel compiles appears to take less time (down from > 3m20 to 2m50), which might make sense as that uses iterators a lot - but > there are too many variables in that for that to be a good benchmark (I'm > dealing with a remote server, for a start). > > Can someone recommend a good way to benchmark this properly? The problem > is that the difference this makes relative to the amount of time taken to > actually do I/O is tiny. I find enough of iov overhead running fio/t/io_uring.c with nullblk. Not sure whether it'll help you but worth a try. > > I've tried TCP transfers using the following sink program: > > #include > #include > #include > #include > #include > #include > #define OSERROR(X, Y) do { if ((long)(X) == -1) { perror(Y); exit(1); } } while(0) > static unsigned char buffer[512 * 1024] __attribute__((aligned(4096))); > int main(int argc, char *argv[]) > { > struct sockaddr_in sin = { .sin_family = AF_INET, .sin_port = htons(5555) }; > int sfd, afd; > sfd = socket(AF_INET, SOCK_STREAM, 0); > OSERROR(sfd, "socket"); > OSERROR(bind(sfd, (struct sockaddr *)&sin, sizeof(sin)), "bind"); > OSERROR(listen(sfd, 1), "listen"); > for (;;) { > afd = accept(sfd, NULL, NULL); > if (afd != -1) { > while (read(afd, buffer, sizeof(buffer)) > 0) {} > close(afd); > } > } > } > > and send program: > > #include > #include > #include > #include > #include > #include > #include > #include > #include > #define OSERROR(X, Y) do { if ((long)(X) == -1) { perror(Y); exit(1); } } while(0) > static unsigned char buffer[512*1024] __attribute__((aligned(4096))); > int main(int argc, char *argv[]) > { > struct sockaddr_in sin = { .sin_family = AF_INET, .sin_port = htons(5555) }; > struct hostent *h; > ssize_t size, r, o; > int cfd; > if (argc != 3) { > fprintf(stderr, "tcp-gen \n"); > exit(2); > } > size = strtoul(argv[2], NULL, 0); > if (size <= 0) { > fprintf(stderr, "Bad size\n"); > exit(2); > } > h = gethostbyname(argv[1]); > if (!h) { > fprintf(stderr, "%s: %s\n", argv[1], hstrerror(h_errno)); > exit(3); > } > if (!h->h_addr_list[0]) { > fprintf(stderr, "%s: No addresses\n", argv[1]); > exit(3); > } > memcpy(&sin.sin_addr, h->h_addr_list[0], h->h_length); > cfd = socket(AF_INET, SOCK_STREAM, 0); > OSERROR(cfd, "socket"); > OSERROR(connect(cfd, (struct sockaddr *)&sin, sizeof(sin)), "connect"); > do { > r = size > sizeof(buffer) ? sizeof(buffer) : size; > size -= r; > o = 0; > do { > ssize_t w = write(cfd, buffer + o, r - o); > OSERROR(w, "write"); > o += w; > } while (o < r); > } while (size > 0); > OSERROR(close(cfd), "close/c"); > return 0; > } > > since the socket interface uses iterators. It seems to show no difference. > One side note, though: I've been doing 10GiB same-machine transfers, and it > takes either ~2.5s or ~0.87s and rarely in between, with or without these > patches, alternating apparently randomly between the two times. > > The patches can be found here: > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-ops > > David > --- > David Howells (29): > iov_iter: Switch to using a table of operations > iov_iter: Split copy_page_to_iter() > iov_iter: Split iov_iter_fault_in_readable > iov_iter: Split the iterate_and_advance() macro > iov_iter: Split copy_to_iter() > iov_iter: Split copy_mc_to_iter() > iov_iter: Split copy_from_iter() > iov_iter: Split the iterate_all_kinds() macro > iov_iter: Split copy_from_iter_full() > iov_iter: Split copy_from_iter_nocache() > iov_iter: Split copy_from_iter_flushcache() > iov_iter: Split copy_from_iter_full_nocache() > iov_iter: Split copy_page_from_iter() > iov_iter: Split iov_iter_zero() > iov_iter: Split copy_from_user_atomic() > iov_iter: Split iov_iter_advance() > iov_iter: Split iov_iter_revert() > iov_iter: Split iov_iter_single_seg_count() > iov_iter: Split iov_iter_alignment() > iov_iter: Split iov_iter_gap_alignment() > iov_iter: Split iov_iter_get_pages() > iov_iter: Split iov_iter_get_pages_alloc() > iov_iter: Split csum_and_copy_from_iter() > iov_iter: Split csum_and_copy_from_iter_full() > iov_iter: Split csum_and_copy_to_iter() > iov_iter: Split iov_iter_npages() > iov_iter: Split dup_iter() > iov_iter: Split iov_iter_for_each_range() > iov_iter: Remove iterate_all_kinds() and iterate_and_advance() > > > lib/iov_iter.c | 1440 +++++++++++++++++++++++++++++++----------------- > 1 file changed, 934 insertions(+), 506 deletions(-) > > -- Pavel Begunkov