From patchwork Mon Jan 29 14:27:56 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13535748 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 CFBC166B45 for ; Mon, 29 Jan 2024 14:28:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706538492; cv=none; b=a47QaVfruZz1ulPvxhP1qn85Qwej7ugNEFN+eyZt7J0VL1MiqFbLgW0XQX9IKQjAJ1NjFT3zhB8DfDvsdvJ0MVIV8ODGRFDGKwq4lQ7+EKYZpf26orEgdZMuPBIVHh5MfyBSgYhjyo00Cx0M3NUM7hH5XJrLOtxfsSHAF2sWyU4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706538492; c=relaxed/simple; bh=08vMVQVJ1OL1ZrKwTC27MiT2Y0Q66IzGXt2K5LTQM9o=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=Km4mpIgXPcO/zAgp35vdkwKUu7Bmikz0UvAk2XyDpC0KDqRXGtHeWPvWiRHAiBUB2yu+aNqE7vrO4jdp2y2lTXYt5SKt12KZBi0hf9/oHu1YngdVUteJ4RgUZOG7ikMbf7uY2Ua7UB1RolZNLW65olm4yEkN9dyIQ5BDSOk2gA4= 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=K3LyIwYC; arc=none smtp.client-ip=209.85.219.202 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="K3LyIwYC" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dc693399655so578833276.1 for ; Mon, 29 Jan 2024 06:28:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1706538490; x=1707143290; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=m6ix6w6jnc/r7m37oFEuHsrF8vE57HFuEmsPVrjGUaM=; b=K3LyIwYCK+G+Lo6hvBHjsL9NoQkKrNa0sqARrSDIjLJYoi1XfrwYBcvOy3VFGOuf3m iAefHLZWq7bbKHchUPh4fhgot3cD45M/+w1kxRrVSY0SpNi1tG5Ps4Xu+437n1Fuy2Tr B7vD69eoNZ5wNW4Lj/XkkcSDXOOCVUzc86rmImpwiIwse2WP1nYzkjpDa5UNqeEfQ+Cv oU7FaughFLMILAZ4UuJV6nbUzsMcXEquOVVYJri49nIt9GZHHMoLODj0QpQqlVwgg6kY IV+FzokgR2jr5mal2YU4g6qkFq8SxQISC6IDASozwQ3aREj3h3ZYglOiZg1LOH4CwhT0 7LEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706538490; x=1707143290; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=m6ix6w6jnc/r7m37oFEuHsrF8vE57HFuEmsPVrjGUaM=; b=rMg5Jb+/4+qozX+e9ILd/Qvy89IjpVo6y+z5030Y2idO9CTU1jJw+g2HbyN/oNbMye WyS/8a4xH1Wragv7lRG0ulIR82VZMkfqPDcVkUpvWWPQNLzUnzfo1dYoxpPPv2pbO+ay b4sY0CnTKYZiFoUk1SeFcbHltFli/fq3ljNNSULnPQnpEYmXAiBWsjBHjncD36oY/zEi XBQP3C9qjcCNn2aOHY9+yCpcvNF3kQKdDTHgsgPeRe1GZDpJsbOkAu4wOGNdw8SLKo1T aKrRy7bXXn2D1dZafJ/E6Tl7ed14fXkVkqROxVLI8UMttGlAzxJ88H/rpaL2ljoxTKci Ba6Q== X-Gm-Message-State: AOJu0YzkZV2t3XzLo2G4mX+MtRTy46ucDhAqObEwn2KTWpZ+kifL4Vjs dDpFHjL6cItazTgatjqyBrcylHUGSiGnJN/phHL/kzx1TaTjITE/4xtuL/sFNDuCPsnF6pevLWh PAP4lhMhak3jAXt4jQg== X-Google-Smtp-Source: AGHT+IFte0IYVAormlKW9S1uv8ALJPhQWbkSghp060KwuGekaE6Nm2aCF6VUI2ioQZuqMFJyJ+SRN1kWtMrBxlQh X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:6902:e0d:b0:dc6:785:1a10 with SMTP id df13-20020a0569020e0d00b00dc607851a10mr2227607ybb.4.1706538489812; Mon, 29 Jan 2024 06:28:09 -0800 (PST) Date: Mon, 29 Jan 2024 14:27:56 +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 2.43.0.429.g432eaa2c6b-goog Message-ID: <20240129142802.2145305-1-vdonnefort@google.com> Subject: [PATCH v13 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 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. (29142dc92c37d3259a33aef15b03e6ee25b0d188) * 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 | 45 +++ kernel/trace/ring_buffer.c | 335 +++++++++++++++++- kernel/trace/trace.c | 210 ++++++++++- kernel/trace/trace.h | 6 + kernel/trace/trace_events_trigger.c | 58 ++- tools/testing/selftests/ring-buffer/Makefile | 8 + tools/testing/selftests/ring-buffer/config | 1 + .../testing/selftests/ring-buffer/map_test.c | 183 ++++++++++ 11 files changed, 918 insertions(+), 40 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: 29142dc92c37d3259a33aef15b03e6ee25b0d188