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=-3.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=no 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 4AF29C35E01 for ; Tue, 25 Feb 2020 16:04:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C53E2072D for ; Tue, 25 Feb 2020 16:04:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="0AVP48gz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728065AbgBYQEy (ORCPT ); Tue, 25 Feb 2020 11:04:54 -0500 Received: from mail-io1-f45.google.com ([209.85.166.45]:33121 "EHLO mail-io1-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728051AbgBYQEy (ORCPT ); Tue, 25 Feb 2020 11:04:54 -0500 Received: by mail-io1-f45.google.com with SMTP id z8so2817709ioh.0 for ; Tue, 25 Feb 2020 08:04:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Caji5YTxOgnbPSqZrj8z1cApQfcaGFZJrBeZgVjpkkc=; b=0AVP48gzAoyhAoENVv9a25DW5nYx23n8iFwB3/n5zJNCz4Z/juWJcUpgGWhP6ZSn6J vmlxmz9S/xuL1vgtKi2Cr1bB96aqh4t5tG+C3YIoLd8w9kRSO2XN5omocPuCAZGlHZuo u7XmQwc/nQEWsB+PSOEkMpjIhTbWYaUu74qvQwIER86Zke2hYpO3I4MPG5bIUqCZ0XgI 6+GbVeFW8CqOjQeYf51uHMWDf2HIummAxrvOF2yknbAsQcrUxU+4wbRArJQ9KoU6FGPt xtHFdz+kFX90nh5BAfZBPNvAcReOo1nmmAsE9kVbnwdmNi61ci/qNZn91kMQgU2CIyMU px+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Caji5YTxOgnbPSqZrj8z1cApQfcaGFZJrBeZgVjpkkc=; b=PSx1PuCmxEAPPZ3buGPCtdEF9QIorvkSQwubF1GHv/wiqbyRtAsr2DeQR85YZ0im5Y DQ47z71cvZkTWdxLsalkk8rEYZ7gIxD+6jx7uUvwLthNN7HvJ6XqWsf1L9Kv8IgTesDh G8x0XNSg1nacrlnd06XRAovP6vnv/PtUMfOTBH574OQnaPL15I8Era/mPGhJ0TgJFLq2 /AyReC6c33m61GQuUf/dHQdwsFbISOu7naWBK4+Rd/KGDUXafnQ+YcWjiSuz3VQQJKhU 8yHJ4PIaH2prLqKh2XUFDNaF66dDpzwT4L83dDbW87veIlS3irsEze1gr65ZMBdTGNX7 cfyw== X-Gm-Message-State: APjAAAVFfAWr0gOshBcCMIytrow5WJ07A83LoE1q+uovRhOLT2x8EWKc VpvEW/IXWzQoLV07MFT+WCMppxsnX7k= X-Google-Smtp-Source: APXvYqxHV7ajesHsnhcYlbAYs26Uk1Hdbx6ksOSDotzYUPLpwFTFpvmnZuisgNB7YuYuy8uWuBIpuw== X-Received: by 2002:a05:6638:72c:: with SMTP id j12mr61572580jad.136.1582646693553; Tue, 25 Feb 2020 08:04:53 -0800 (PST) Received: from x1.localdomain ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id k23sm5628100ilg.83.2020.02.25.08.04.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2020 08:04:53 -0800 (PST) From: Jens Axboe To: io-uring@vger.kernel.org Cc: andres@anarazel.de Subject: [PATCHSET v2 0/3] io_uring support for automatic buffers Date: Tue, 25 Feb 2020 09:04:48 -0700 Message-Id: <20200225160451.7198-1-axboe@kernel.dk> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org With the poll retry based async IO patchset I posted last week, the one big missing thing for me was the ability to have automatic buffer selection. Generally applications that handle tons of sockets like to poll for activity on them, then issue IO when they become ready. This is of course at least two system calls, but it also means that it provides an application a chance to manage how many IO buffers it needs. With the io_uring based polled IO, the application need only issue an IORING_OP_RECV (for example, to receive socket data), it doesn't need to poll at all. However, this means that the application no longer has an opportune moment to select how many IO buffers to keep in flight, it has to be equal to what it currently has pending. I had originally intended to use BPF to provide some means of buffer selection, but I had a hard time imagining how life times of the buffer could be managed through that. I had a false start today, but Andres suggested a nifty approach that also solves the life time issue. Basically the application registers buffers with the kernel. Each buffer is registered with a given group ID, and buffer ID. The buffers are organized by group ID, and the application selects a buffer pool based on this group ID. One use case might be to group by size. There's an opcode for this, IORING_OP_PROVIDE_BUFFERS. IORING_OP_PROVIDE_BUFFERS takes a start address, length of a buffer, and number of buffers. It also provides a group ID with which these buffers should be associated, and a starting buffer ID. The buffers are then added, and the buffer ID is incremented by 1 for each buffer. With that, when doing the same IORING_OP_RECV, no buffer is passed in with the request. Instead, it's flagged with IOSQE_BUFFER_SELECT, and sqe->buf_group is filled in with a valid group ID. When the kernel can satisfy the receive, a buffer is selected from the specified group ID pool. If none are available, the IO is terminated with -ENOBUFS. On success, the buffer ID is passed back through the (CQE) completion event. This tells the application what specific buffer was used. A buffer can be used only once. On completion, the application may choose to free it, or register it again with IORING_OP_PROVIDE_BUFFER. Patches can also be found in the below repo: https://git.kernel.dk/cgit/linux-block/log/?h=io_uring-buf-select and they are obviously layered on top of the poll retry rework. Changes since v1: - Cleanup address space - Fix locking for async offload issue - Add lockdep annotation for uring_lock - Verify sqe fields on PROVIDE_BUFFERS prep - Fix send/recv kbuf leak on import failure - Fix send/recv error handling on -ENOBUFS - Change IORING_OP_PROVIDE_BUFFER to PROVIDE_BUFFERS, and allow multiple contig buffers in one call -- Jens Axboe