From patchwork Mon Feb 5 16:34:04 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13545837 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 22CE43FE3D for ; Mon, 5 Feb 2024 16:34:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707150859; cv=none; b=i8JUSAsWPYMjbCuhXTSweFleB7B1DeRRSmKChZ9HES15QMPwiJPzywFzZq/0zSTZmlEYiXDOTGlD5f9cOggf+Z03YHym6ggqu1KmL+1x+GNwx/JcPBstv/VsXJdyVjq/EajAR3SZ5UTolQLd3Bx5sV+49p5GqnfdvLSAnUnogTw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707150859; c=relaxed/simple; bh=tZH2CeWzrF3LXwnsAv3jlMz5yaTDBOLavgTl2tFS9Bw=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=p8SUzHy3Clb8hnyBVD7hq3u0aFPNx22YjjbSElz27/xjJB/S9wYdNlMS6y2R9qyKAieR+LAR+VHwXlN+JymfreYMjLn+fSMWrBX8vv9vURC1EbQCYM3fIBj6oZwtjKi8NEsPcs/TwR07Jh7bjk9iVx9ThN/BTXpNQN+QHuD+GqQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=h7zxTkwI; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="h7zxTkwI" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-60444884b7dso24607197b3.1 for ; Mon, 05 Feb 2024 08:34:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1707150857; x=1707755657; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=PpJg+QSlnAWjjgOu3uofSR4E+hbgVBBN+bxzotDQEwU=; b=h7zxTkwIPDVLSvQDiWVx0qoiCXeDyGBbg59emV4SQrmdy+o518eMcsw2FcUdo5Lxuc QjTSLc78kmu/HqjEcn2NSnglU88w6ZecNspy+nOcJpl0WjjbANP3d35USNQbvFMzZtKk L1iaNyMclrBX6DYij7iG7DpGTPzlOgrw97cDgg9vi5rFThLIJfiHN/c6oVmjLVlxcBZB onT9QqSNY15IWcSLFPK6rzEjEtHbdFyocbuz5AUcPK0sAouDqZBj+CMF5tGDwQYGLpcb zE+/KXe/bSGpmhmyw3gX2n7G61jWD3AP/ojikwmFxTDT1U9JaLe/+wWC/FCuB/XZA2Oj Sbpw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707150857; x=1707755657; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=PpJg+QSlnAWjjgOu3uofSR4E+hbgVBBN+bxzotDQEwU=; b=UCAqVGz8s4vdsVbh93MfyX7wtxxke1aAIP/8ojCNR7a6kbPm6ccmrNsLpa1MiwjKX9 Q6emcZaIMvsA9C7ULZ80MAyHUVnpdbyqK35Tvc6bllxU6q3WnVNqQfluvembT+flnotY kYxpwKt7BhFwYSePArqf8ldZhnpOgzEJTMFM4fU/soPcruFEgF4acOg6sFPNtYkzQeBl kOZojzBiiLm2Ec6OHJHH4Xj05eJ9u16nS+CahHOMUk//IHuLmSmqikddXXqCcezNyVlf TTENghbYUSMo/btfIAuHvHvwWp1ktcGzkM1neFzUaYuw5ZKw2cDU/KinFS4cCmTzo7Ow J4Xg== X-Gm-Message-State: AOJu0YwfpDw/rF7Y3y9eaNeZn6c6NKyWRLrarHbmNAsUONXwNA87txP8 8E8LvjQbnGmxxwASYE/Cfpfp/PQ/3SwZrBvVgF+XPAukfx8UTf9dFSB0K08tF44pX+m7lMumQ0P 94bWHUYPryGpQbLwbYQ== X-Google-Smtp-Source: AGHT+IG9xRk/6XYsAS/orOHiz14UWutRLC9DGTBH6qjHxKsZJYds5u1iBQZr5mgmGlxbRyMQSvoRQspIEUVm1m1n X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:6902:10cd:b0:dc6:e647:3fae with SMTP id w13-20020a05690210cd00b00dc6e6473faemr448377ybu.2.1707150857143; Mon, 05 Feb 2024 08:34:17 -0800 (PST) Date: Mon, 5 Feb 2024 16:34:04 +0000 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.43.0.594.gd9cf4e227d-goog Message-ID: <20240205163410.2296552-1-vdonnefort@google.com> Subject: [PATCH v14 0/6] Introducing trace buffer mapping by user-space From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, Vincent Donnefort The tracing ring-buffers can be stored on disk or sent to network without any copy via splice. However the later doesn't allow real time processing of the traces. A solution is to give userspace direct access to the ring-buffer pages via a mapping. An application can now become a consumer of the ring-buffer, in a similar fashion to what trace_pipe offers. Support for this new feature can already be found in libtracefs from version 1.8, when built with EXTRA_CFLAGS=-DFORCE_MMAP_ENABLE. Vincent v13 -> v14: * All cpu_buffer->mapped readers use READ_ONCE (except for swap_cpu) * on unmap, sync meta-page teardown with the reader_lock instead of the synchronize_rcu. * Add a dedicated spinlock for trace_array ->snapshot and ->mapped. (intends to fix a lockdep issue) * Add kerneldoc for flags and Reserved fields. * Add kselftest for snapshot/map mutual exclusion. v12 -> v13: * Swap subbufs_{touched,lost} for Reserved fields. * Add a flag field in the meta-page. * Fix CONFIG_TRACER_MAX_TRACE. * Rebase on top of trace/urgent. * Add a comment for try_unregister_trigger() v11 -> v12: * Fix code sample mmap bug. * Add logging in sample code. * Reset tracer in selftest. * Add a refcount for the snapshot users. * Prevent mapping when there are snapshot users and vice versa. * Refine the meta-page. * Fix types in the meta-page. * Collect Reviewed-by. v10 -> v11: * Add Documentation and code sample. * Add a selftest. * Move all the update to the meta-page into a single rb_update_meta_page(). * rb_update_meta_page() is now called from ring_buffer_map_get_reader() to fix NOBLOCK callers. * kerneldoc for struct trace_meta_page. * Add a patch to zero all the ring-buffer allocations. v9 -> v10: * Refactor rb_update_meta_page() * In-loop declaration for foreach_subbuf_page() * Check for cpu_buffer->mapped overflow v8 -> v9: * Fix the unlock path in ring_buffer_map() * Fix cpu_buffer cast with rb_work_rq->is_cpu_buffer * Rebase on linux-trace/for-next (3cb3091138ca0921c4569bcf7ffa062519639b6a) v7 -> v8: * Drop the subbufs renaming into bpages * Use subbuf as a name when relevant v6 -> v7: * Rebase onto lore.kernel.org/lkml/20231215175502.106587604@goodmis.org/ * Support for subbufs * Rename subbufs into bpages v5 -> v6: * Rebase on next-20230802. * (unsigned long) -> (void *) cast for virt_to_page(). * Add a wait for the GET_READER_PAGE ioctl. * Move writer fields update (overrun/pages_lost/entries/pages_touched) in the irq_work. * Rearrange id in struct buffer_page. * Rearrange the meta-page. * ring_buffer_meta_page -> trace_buffer_meta_page. * Add meta_struct_len into the meta-page. v4 -> v5: * Trivial rebase onto 6.5-rc3 (previously 6.4-rc3) v3 -> v4: * Add to the meta-page: - pages_lost / pages_read (allow to compute how full is the ring-buffer) - read (allow to compute how many entries can be read) - A reader_page struct. * Rename ring_buffer_meta_header -> ring_buffer_meta * Rename ring_buffer_get_reader_page -> ring_buffer_map_get_reader_page * Properly consume events on ring_buffer_map_get_reader_page() with rb_advance_reader(). v2 -> v3: * Remove data page list (for non-consuming read) ** Implies removing order > 0 meta-page * Add a new meta page field ->read * Rename ring_buffer_meta_page_header into ring_buffer_meta_header v1 -> v2: * Hide data_pages from the userspace struct * Fix META_PAGE_MAX_PAGES * Support for order > 0 meta-page * Add missing page->mapping. Vincent Donnefort (6): ring-buffer: Zero ring-buffer sub-buffers ring-buffer: Introducing ring-buffer mapping functions tracing: Add snapshot refcount tracing: Allow user-space mapping of the ring-buffer Documentation: tracing: Add ring-buffer mapping ring-buffer/selftest: Add ring-buffer mapping test Documentation/trace/index.rst | 1 + Documentation/trace/ring-buffer-map.rst | 104 ++++++ include/linux/ring_buffer.h | 7 + include/uapi/linux/trace_mmap.h | 48 +++ kernel/trace/ring_buffer.c | 344 +++++++++++++++++- kernel/trace/trace.c | 221 +++++++++-- kernel/trace/trace.h | 9 +- kernel/trace/trace_events_trigger.c | 58 ++- tools/testing/selftests/ring-buffer/Makefile | 8 + tools/testing/selftests/ring-buffer/config | 2 + .../testing/selftests/ring-buffer/map_test.c | 273 ++++++++++++++ 11 files changed, 1029 insertions(+), 46 deletions(-) create mode 100644 Documentation/trace/ring-buffer-map.rst create mode 100644 include/uapi/linux/trace_mmap.h create mode 100644 tools/testing/selftests/ring-buffer/Makefile create mode 100644 tools/testing/selftests/ring-buffer/config create mode 100644 tools/testing/selftests/ring-buffer/map_test.c base-commit: e2412e51fdea837b50ce31fea8e5dfc885237f3a