From patchwork Fri Feb 9 10:21:56 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13551024 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (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 35B336996E for ; Fri, 9 Feb 2024 10:22:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707474133; cv=none; b=W3vEy6VuBHDDtgpONeYnzLA1DO7S1X8jcDssUQ9fD2db/gVuBjocvNkrMrXfJJepcMynZl1Yi1jHuSj3bDTetrW/z4dNdMyJzc9OdbgSuWMpoB+LV3wOObnxXTbwlZYsm36lPJPMeaVBPtMarjy7KuYJ67GZr/lgdLbBXTn7XXw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707474133; c=relaxed/simple; bh=qxJhumotfzjeTVZ55n5PKmjmcyo982hoJ1QPQeDy8UU=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=uBLpKG+2fhrrXrmpZ2svQypjWlK5rRf/x35DVnXj7XRj4k8ZM6KWsogYVRYf3+5/PPw9q4utQnkZzS+iXbKlYlzsTp0W5fkzluazPrfBf7D5ZYuCMfaLG8NZOP9ji+HBHFs2Eo2iu9emtbH+gUpR0hiQQz4tBKXrH4dewcfE3zE= 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=Sum5qYrR; arc=none smtp.client-ip=209.85.128.201 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="Sum5qYrR" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-60492d6bfc0so14194917b3.2 for ; Fri, 09 Feb 2024 02:22:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1707474131; x=1708078931; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=Ykp0H7Zv6C2KOkWrdkAm5rJrFsTMhgnYXj5UC2NL3Ic=; b=Sum5qYrRAqPYgj1icsn/qLF6v20zis6BMndLYug1E7ILHS2DHmX5olriOH8eiGJ/eg LLn0WSnaV8Nrda61XrqKRju3WAzl69FFOqndXldys32Vlw8jnMxcABQ3ywXjz4xUIpTA pczRiUCwZrDRpt/IUXrR7NcWwvruw618WjFjkzLYD4UnDiTzx1AP0X+vdupbfEdmm9t1 pTYV+EPAx+FEtHXZSFkDsOO8Z53BxbLrzEaA7WygNhlkLymmgqXtaiobEqDBVG2e1PJr eFhan8zrysmgFfOgiHwV/aA3Lq087tWSxY1f82exQ9GlIcqWLia/CLPNOUQWa2i7BEMC iqTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707474131; x=1708078931; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=Ykp0H7Zv6C2KOkWrdkAm5rJrFsTMhgnYXj5UC2NL3Ic=; b=wK5sOAE0L796qZnWAopqpMa1iI9UuCCYzvaQ3YHLhCQUPhC2LJ++cRCdLgEMgJ/nuP Jlz+RbK0Y8HDZZksv/oMByJSWrKfmvWVW/0TMWn8MWosxtuDorCPm9wclz9dSKGhgXmh ycW31JG/fvPKDKUtxTRv+rP6evftEPvbCUh/zFMmSE3nP4uhdoMkV4php+uptKrHANeY 6LUWLvbO8sweTVRfLGQrHZfJYQcL9qRAJDVQ+WVxDJMILGngrMFtA6Mw00q1HofQihJn tqGFSb7BhR6B7pVuLEQGYtkVAld8p5TZNMN43CmpMOaomTgJFStxY+/zvEJGyrIW/oKA soLQ== X-Gm-Message-State: AOJu0YxiUcO4/Z4PcVFnianLIh349TJrlf/UUmMr+YXxsZiN6VYEmFuL aW5TCJQk3yqBMw7HWLcm/jUWGRUUX5aOGluH3lu3DPOuLfXsV00RlWko+8ZaUxwE5eaqsBbhU2E lqD/V9S40b6acyA/ubQ== X-Google-Smtp-Source: AGHT+IHenUou1H2Fm7+c/27dCYqsj3x3wxGdPS2prYEzdDzDon3dWjp5qzuJb8jAol+N7nDfjplcTBz/YwqYgMSm X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:690c:368e:b0:604:b83:9cad with SMTP id fu14-20020a05690c368e00b006040b839cadmr177147ywb.5.1707474131271; Fri, 09 Feb 2024 02:22:11 -0800 (PST) Date: Fri, 9 Feb 2024 10:21:56 +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 2.43.0.687.g38aa6559b0-goog Message-ID: <20240209102202.649049-1-vdonnefort@google.com> Subject: [PATCH v15 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 v14 -> v15: * Add meta-page and reader-page flush. Intends to fix the mapping for VIVT and aliasing-VIPT data caches. * -EPERM on VM_EXEC. * Fix build warning !CONFIG_TRACER_MAX_TRACE. 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 | 349 +++++++++++++++++- 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, 1034 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: ca185770db914869ff9fe773bac5e0e5e4165b83