From patchwork Mon Feb 11 19:00:45 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 10806693 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CFEF617FB for ; Mon, 11 Feb 2019 19:01:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BFAC22AE23 for ; Mon, 11 Feb 2019 19:01:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B18BD2B243; Mon, 11 Feb 2019 19:01:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B39A8293A8 for ; Mon, 11 Feb 2019 19:01:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387472AbfBKTB0 (ORCPT ); Mon, 11 Feb 2019 14:01:26 -0500 Received: from mail-it1-f196.google.com ([209.85.166.196]:51694 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387473AbfBKTBY (ORCPT ); Mon, 11 Feb 2019 14:01:24 -0500 Received: by mail-it1-f196.google.com with SMTP id y184so925482itc.1 for ; Mon, 11 Feb 2019 11:01:23 -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:in-reply-to:references; bh=X+kfFxgsbJ5SWhuSmmeD8j2b8pHrlDNcu4HQ+LPuogI=; b=Unki+2umPEGB8yl3twOKO8a8Ab7RHlwk4Bdt3nxaFy9wfmw6/hd5bWZ/nJUDuQrvTU y88nTrFvgD6nkEceSv7JAYvo9xTAK+D4Ye5wqVGEEFpdZpQtKjn5j9B5XvivIUwEEG2y WxMNUjAmylQweCjuYgA0+H4STCgyu8aJNFYqDbb9dyr2KrKURpCX1ia1e/zNlIfsfeq2 MAG+PKP8yUAvgGWx+pXwY7VEZQhorGrwAixU4maDyu66HnUrwiNbmr6faXaNFyOsRV3G iNsFX3tKfSCkqpqThSpUng10frBG47M7HWMq6TaAp9Fl/0lQvxPfR1/bFNB1Db151pf6 e8iw== 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:in-reply-to :references; bh=X+kfFxgsbJ5SWhuSmmeD8j2b8pHrlDNcu4HQ+LPuogI=; b=PYjnYjsuNZeML9FjuWHpQq9RYlNrbdDsEMHdqYMUKSjOlCh1L1iO2NR00VcgGxO1cI sSGygQaFFBAXJcSFtmMlTs+WvBC3lC+23qcbxFAt2u7GadxaKKqFVThtg4axm50VFg48 VxL06L6d1jkE+iJrTDD70IiUZ1F/VK/NjIhtR51AUJGGTqvVKMQBMKMhvzdAuVKdsS4y NQ/wDrRHJwIHJrUyUiJG+10vKtIPBzPoWW/0bTvIsD+0dmIPma72NC77tiaHW3KhwJVO 6/Bre1+BXe03xUsZXZAABZc9Ay5ryS7h8trzO1UGgfq2kBqEMkPT1CTmqDTSVPySN6rv z6bA== X-Gm-Message-State: AHQUAublpmefyaDEJczGcKMa5fJZZYFK2qkM/wlXfyYJFJe0JGFiWiWf R8lSOtq0QnBFR2qbhzoiu/SbCg== X-Google-Smtp-Source: AHgI3IZZqAM9NZEBjMLqgC7MDRfG5Lz9BDRmPTT2zz5n9AGliq0dAGiyv81eRhZ1TfkTm89e26Gr7Q== X-Received: by 2002:a6b:8bcd:: with SMTP id n196mr18842996iod.295.1549911683227; Mon, 11 Feb 2019 11:01:23 -0800 (PST) Received: from x1.localdomain ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id h184sm62446ith.41.2019.02.11.11.01.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Feb 2019 11:01:22 -0800 (PST) From: Jens Axboe To: linux-aio@kvack.org, linux-block@vger.kernel.org, linux-api@vger.kernel.org Cc: hch@lst.de, jmoyer@redhat.com, avi@scylladb.com, jannh@google.com, viro@ZenIV.linux.org.uk, Jens Axboe Subject: [PATCH 15/19] io_uring: add submission polling Date: Mon, 11 Feb 2019 12:00:45 -0700 Message-Id: <20190211190049.7888-17-axboe@kernel.dk> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190211190049.7888-1-axboe@kernel.dk> References: <20190211190049.7888-1-axboe@kernel.dk> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This enables an application to do IO, without ever entering the kernel. By using the SQ ring to fill in new sqes and watching for completions on the CQ ring, we can submit and reap IOs without doing a single system call. The kernel side thread will poll for new submissions, and in case of HIPRI/polled IO, it'll also poll for completions. By default, we allow 1 second of active spinning. This can by changed by passing in a different grace period at io_uring_register(2) time. If the thread exceeds this idle time without having any work to do, it will set: sq_ring->flags |= IORING_SQ_NEED_WAKEUP. The application will have to call io_uring_enter() to start things back up again. If IO is kept busy, that will never be needed. Basically an application that has this feature enabled will guard it's io_uring_enter(2) call with: read_barrier(); if (*sq_ring->flags & IORING_SQ_NEED_WAKEUP) io_uring_enter(fd, 0, 0, IORING_ENTER_SQ_WAKEUP); instead of calling it unconditionally. It's mandatory to use fixed files with this feature. Failure to do so will result in the application getting an -EBADF CQ entry when submitting IO. Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe --- fs/io_uring.c | 248 +++++++++++++++++++++++++++++++++- include/uapi/linux/io_uring.h | 12 +- 2 files changed, 252 insertions(+), 8 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 167c7f96666f..24c280076e81 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -44,6 +44,7 @@ #include #include #include +#include #include #include #include @@ -108,12 +109,16 @@ struct io_ring_ctx { unsigned cached_sq_head; unsigned sq_entries; unsigned sq_mask; + unsigned sq_thread_idle; struct io_uring_sqe *sq_sqes; } ____cacheline_aligned_in_smp; /* IO offload */ struct workqueue_struct *sqo_wq; + struct task_struct *sqo_thread; /* if using sq thread polling */ struct mm_struct *sqo_mm; + wait_queue_head_t sqo_wait; + unsigned sqo_stop; struct { /* CQ ring */ @@ -168,6 +173,7 @@ struct sqe_submit { unsigned short index; bool has_user; bool needs_lock; + bool needs_fixed_file; }; struct io_kiocb { @@ -327,6 +333,8 @@ static void io_cqring_add_event(struct io_ring_ctx *ctx, u64 ki_user_data, if (waitqueue_active(&ctx->wait)) wake_up(&ctx->wait); + if (waitqueue_active(&ctx->sqo_wait)) + wake_up(&ctx->sqo_wait); } static void io_ring_drop_ctx_refs(struct io_ring_ctx *ctx, unsigned refs) @@ -680,9 +688,10 @@ static bool io_file_supports_async(struct file *file) return false; } -static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, +static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s, bool force_nonblock, struct io_submit_state *state) { + const struct io_uring_sqe *sqe = s->sqe; struct io_ring_ctx *ctx = req->ctx; struct kiocb *kiocb = &req->rw; unsigned ioprio, flags; @@ -702,6 +711,8 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, kiocb->ki_filp = ctx->user_files[fd]; req->flags |= REQ_F_FIXED_FILE; } else { + if (s->needs_fixed_file) + return -EBADF; kiocb->ki_filp = io_file_get(state, fd); if (unlikely(!kiocb->ki_filp)) return -EBADF; @@ -865,7 +876,7 @@ static ssize_t io_read(struct io_kiocb *req, const struct sqe_submit *s, struct file *file; ssize_t ret; - ret = io_prep_rw(req, s->sqe, force_nonblock, state); + ret = io_prep_rw(req, s, force_nonblock, state); if (ret) return ret; file = kiocb->ki_filp; @@ -909,7 +920,7 @@ static ssize_t io_write(struct io_kiocb *req, const struct sqe_submit *s, struct file *file; ssize_t ret; - ret = io_prep_rw(req, s->sqe, force_nonblock, state); + ret = io_prep_rw(req, s, force_nonblock, state); if (ret) return ret; /* Hold on to the file for -EAGAIN */ @@ -1295,6 +1306,170 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) return false; } +static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes, + unsigned int nr, bool has_user, bool mm_fault) +{ + struct io_submit_state state, *statep = NULL; + int ret, i, submitted = 0; + + if (nr > IO_PLUG_THRESHOLD) { + io_submit_state_start(&state, ctx, nr); + statep = &state; + } + + for (i = 0; i < nr; i++) { + if (unlikely(mm_fault)) { + ret = -EFAULT; + } else { + sqes[i].has_user = has_user; + sqes[i].needs_lock = true; + sqes[i].needs_fixed_file = true; + ret = io_submit_sqe(ctx, &sqes[i], statep); + } + if (!ret) { + submitted++; + continue; + } + + io_cqring_add_event(ctx, sqes[i].sqe->user_data, ret, 0); + } + + if (statep) + io_submit_state_end(&state); + + return submitted; +} + +static int io_sq_thread(void *data) +{ + struct sqe_submit sqes[IO_IOPOLL_BATCH]; + struct io_ring_ctx *ctx = data; + struct mm_struct *cur_mm = NULL; + mm_segment_t old_fs; + DEFINE_WAIT(wait); + unsigned inflight; + unsigned long timeout; + + old_fs = get_fs(); + set_fs(USER_DS); + + timeout = inflight = 0; + while (!kthread_should_stop() && !ctx->sqo_stop) { + bool all_fixed, mm_fault = false; + int i; + + if (inflight) { + unsigned nr_events = 0; + + if (ctx->flags & IORING_SETUP_IOPOLL) { + /* + * We disallow the app entering submit/complete + * with polling, but we still need to lock the + * ring to prevent racing with polled issue + * that got punted to a workqueue. + */ + mutex_lock(&ctx->uring_lock); + io_iopoll_check(ctx, &nr_events, 0); + mutex_unlock(&ctx->uring_lock); + } else { + /* + * Normal IO, just pretend everything completed. + * We don't have to poll completions for that. + */ + nr_events = inflight; + } + + inflight -= nr_events; + if (!inflight) + timeout = jiffies + ctx->sq_thread_idle; + } + + if (!io_get_sqring(ctx, &sqes[0])) { + /* + * We're polling. If we're within the defined idle + * period, then let us spin without work before going + * to sleep. + */ + if (inflight || !time_after(jiffies, timeout)) { + cpu_relax(); + continue; + } + + /* + * Drop cur_mm before scheduling, we can't hold it for + * long periods (or over schedule()). Do this before + * adding ourselves to the waitqueue, as the unuse/drop + * may sleep. + */ + if (cur_mm) { + unuse_mm(cur_mm); + mmput(cur_mm); + cur_mm = NULL; + } + + prepare_to_wait(&ctx->sqo_wait, &wait, + TASK_INTERRUPTIBLE); + + /* Tell userspace we may need a wakeup call */ + ctx->sq_ring->flags |= IORING_SQ_NEED_WAKEUP; + smp_wmb(); + + if (!io_get_sqring(ctx, &sqes[0])) { + if (kthread_should_stop()) { + finish_wait(&ctx->sqo_wait, &wait); + break; + } + if (signal_pending(current)) + flush_signals(current); + schedule(); + finish_wait(&ctx->sqo_wait, &wait); + + ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP; + smp_wmb(); + continue; + } + finish_wait(&ctx->sqo_wait, &wait); + + ctx->sq_ring->flags &= ~IORING_SQ_NEED_WAKEUP; + smp_wmb(); + } + + i = 0; + all_fixed = true; + do { + if (all_fixed && io_sqe_needs_user(sqes[i].sqe)) + all_fixed = false; + + i++; + if (i == ARRAY_SIZE(sqes)) + break; + } while (io_get_sqring(ctx, &sqes[i])); + + io_commit_sqring(ctx); + + /* Unless all new commands are FIXED regions, grab mm */ + if (!all_fixed && !cur_mm) { + mm_fault = !mmget_not_zero(ctx->sqo_mm); + if (!mm_fault) { + use_mm(ctx->sqo_mm); + cur_mm = ctx->sqo_mm; + } + } + + inflight += io_submit_sqes(ctx, sqes, i, cur_mm != NULL, + mm_fault); + } + + io_iopoll_reap_events(ctx); + + set_fs(old_fs); + if (cur_mm) { + unuse_mm(cur_mm); + mmput(cur_mm); + } + return 0; +} + static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit) { struct io_submit_state state, *statep = NULL; @@ -1313,6 +1488,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit) s.has_user = true; s.needs_lock = false; + s.needs_fixed_file = false; ret = io_submit_sqe(ctx, &s, statep); if (ret) { @@ -1534,13 +1710,47 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg, return ret; } -static int io_sq_offload_start(struct io_ring_ctx *ctx) +static int io_sq_offload_start(struct io_ring_ctx *ctx, + struct io_uring_params *p) { int ret; + init_waitqueue_head(&ctx->sqo_wait); mmgrab(current->mm); ctx->sqo_mm = current->mm; + ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle); + if (!ctx->sq_thread_idle) + ctx->sq_thread_idle = HZ; + + ret = -EINVAL; + if (!cpu_possible(p->sq_thread_cpu)) + goto err; + + if (ctx->flags & IORING_SETUP_SQPOLL) { + if (p->flags & IORING_SETUP_SQ_AFF) { + int cpu; + + cpu = array_index_nospec(p->sq_thread_cpu, NR_CPUS); + ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread, + ctx, cpu, + "io_uring-sq"); + } else { + ctx->sqo_thread = kthread_create(io_sq_thread, ctx, + "io_uring-sq"); + } + if (IS_ERR(ctx->sqo_thread)) { + ret = PTR_ERR(ctx->sqo_thread); + ctx->sqo_thread = NULL; + goto err; + } + wake_up_process(ctx->sqo_thread); + } else if (p->flags & IORING_SETUP_SQ_AFF) { + /* Can't have SQ_AFF without SQPOLL */ + ret = -EINVAL; + goto err; + } + /* Do QD, or 2 * CPUS, whatever is smallest */ ctx->sqo_wq = alloc_workqueue("io_ring-wq", WQ_UNBOUND | WQ_FREEZABLE, min(ctx->sq_entries - 1, 2 * num_online_cpus())); @@ -1551,6 +1761,12 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx) return 0; err: + if (ctx->sqo_thread) { + ctx->sqo_stop = 1; + mb(); + kthread_stop(ctx->sqo_thread); + ctx->sqo_thread = NULL; + } mmdrop(ctx->sqo_mm); ctx->sqo_mm = NULL; return ret; @@ -1801,6 +2017,11 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg, static void io_ring_ctx_free(struct io_ring_ctx *ctx) { + if (ctx->sqo_thread) { + ctx->sqo_stop = 1; + mb(); + kthread_stop(ctx->sqo_thread); + } if (ctx->sqo_wq) destroy_workqueue(ctx->sqo_wq); if (ctx->sqo_mm) @@ -1910,7 +2131,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, int submitted = 0; struct fd f; - if (flags & ~IORING_ENTER_GETEVENTS) + if (flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP)) return -EINVAL; f = fdget(fd); @@ -1926,6 +2147,18 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, if (!percpu_ref_tryget(&ctx->refs)) goto out_fput; + /* + * For SQ polling, the thread will do all submissions and completions. + * Just return the requested submit count, and wake the thread if + * we were asked to. + */ + if (ctx->flags & IORING_SETUP_SQPOLL) { + if (flags & IORING_ENTER_SQ_WAKEUP) + wake_up(&ctx->sqo_wait); + submitted = to_submit; + goto out_ctx; + } + if (to_submit) { to_submit = min(to_submit, ctx->sq_entries); @@ -2103,7 +2336,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) if (ret) goto err; - ret = io_sq_offload_start(ctx); + ret = io_sq_offload_start(ctx, p); if (ret) goto err; @@ -2151,7 +2384,8 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params) return -EINVAL; } - if (p.flags & ~IORING_SETUP_IOPOLL) + if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL | + IORING_SETUP_SQ_AFF)) return -EINVAL; ret = io_uring_create(entries, &p); diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 6257478d55e9..0ec74bab8dbe 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -42,6 +42,8 @@ struct io_uring_sqe { * io_uring_setup() flags */ #define IORING_SETUP_IOPOLL (1U << 0) /* io_context is polled */ +#define IORING_SETUP_SQPOLL (1U << 1) /* SQ poll thread */ +#define IORING_SETUP_SQ_AFF (1U << 2) /* sq_thread_cpu is valid */ #define IORING_OP_NOP 0 #define IORING_OP_READV 1 @@ -86,6 +88,11 @@ struct io_sqring_offsets { __u64 resv2; }; +/* + * sq_ring->flags + */ +#define IORING_SQ_NEED_WAKEUP (1U << 0) /* needs io_uring_enter wakeup */ + struct io_cqring_offsets { __u32 head; __u32 tail; @@ -100,6 +107,7 @@ struct io_cqring_offsets { * io_uring_enter(2) flags */ #define IORING_ENTER_GETEVENTS (1U << 0) +#define IORING_ENTER_SQ_WAKEUP (1U << 1) /* * Passed in for io_uring_setup(2). Copied back with updated info on success @@ -108,7 +116,9 @@ struct io_uring_params { __u32 sq_entries; __u32 cq_entries; __u32 flags; - __u32 resv[7]; + __u32 sq_thread_cpu; + __u32 sq_thread_idle; + __u32 resv[5]; struct io_sqring_offsets sq_off; struct io_cqring_offsets cq_off; };