From patchwork Fri Jan 5 09:47:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13511898 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (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 F361724201 for ; Fri, 5 Jan 2024 09:47:56 +0000 (UTC) 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="LmLOlNsn" Received: by mail-wr1-f73.google.com with SMTP id ffacd0b85a97d-33697cbd035so844631f8f.2 for ; Fri, 05 Jan 2024 01:47:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704448075; x=1705052875; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=q0Ihtvt7Jj4Snjis0kK23Nx0/swAE/PC+E/mPrecld0=; b=LmLOlNsnZmza2P3eYQ8JsQN4FGmhZQX9Bm64JH8qrDZiDhs1LUmwVY8YcsEmmCV7/F hR6czpd0+1+eE467H0ztdmVxfu4XMVuVloxuCeq6OIUn/FfwdZ7qceYLFIwmGn/Wtoa3 +BYe3I0eRPFukzRyvL/G/rKyvCe8VvbOEzLwwMyxrG+pOUNB3xYxnWGlA8YXDwHeeKnS 79YmS4tYuJjMu6EdyvNqWc3lCZexxHR+Q0dtA6VBUQhJ8gRQdEwIVt2T1CjaSJ8Yjnvb 5i6bwRp+eDQ7emL90UiJdwratem+4vYJUJqXwaAQuLYE53z+rM1W1DkOHA2zBAkxR2kp lp/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704448075; x=1705052875; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=q0Ihtvt7Jj4Snjis0kK23Nx0/swAE/PC+E/mPrecld0=; b=o9wMr3CJ02rr3eaRklUAD7JBiiJortQ590djTeyIYoCjcWJiR3xfcERdVq5n9iSxSI YCs07iMKn4yU9sdsrcBSYOCm7mrDicnwOiZbI3Bp8kTyEC7N+jXinYLfH3mL5/V6toft 50wPuXzD8wmL7CqY3YVV1xkthvnT0/DJx9hqu157gtNVmzNhokPy5s/iLkl+JU78LZJq 3ei18pQdEPGFbiv8paCkKesOF6GUfMDZuqIYMad/223bRKmyZApC2uGnyVWE7JbyawHZ frWouDGFQR55hVBSX4foz/vMfueT5dhG/Xj5Lg1xlo/IJyJ4uAey/YvHHqTMOcZSUq6x pRGw== X-Gm-Message-State: AOJu0Yyz8dNtayYLkMa8mbBhYsSXQnAua3c+BRqICWYcrGoCuWIePmBj OWHcP5kE3R7htuVUAVIB0QSWBq/Ihoi6Nxt38GEY55M= X-Google-Smtp-Source: AGHT+IG64AclkTmLjZ3ZiUvCGdQtiKG1ldPrkaBk0dq6wGG+h3Wsm35YjzdWzGU8u+5jW//xLNF+vvuWehnJDCgw X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a5d:64ed:0:b0:336:ec41:8d35 with SMTP id g13-20020a5d64ed000000b00336ec418d35mr8879wri.3.1704448074909; Fri, 05 Jan 2024 01:47:54 -0800 (PST) Date: Fri, 5 Jan 2024 09:47:27 +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 2.43.0.472.g3155946c3a-goog Message-ID: <20240105094729.2363579-1-vdonnefort@google.com> Subject: [PATCH v10 0/2] Introducing trace buffer mapping by user-space From: Vincent Donnefort To: rostedt@goodmis.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mhiramat@kernel.org, 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 in libtracefs can be found here: https://lore.kernel.org/all/20231228201100.78aae259@rorschach.local.home Vincent 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 (2): ring-buffer: Introducing ring-buffer mapping functions tracing: Allow user-space mapping of the ring-buffer include/linux/ring_buffer.h | 7 + include/uapi/linux/trace_mmap.h | 31 +++ kernel/trace/ring_buffer.c | 384 +++++++++++++++++++++++++++++++- kernel/trace/trace.c | 79 ++++++- 4 files changed, 497 insertions(+), 4 deletions(-) create mode 100644 include/uapi/linux/trace_mmap.h base-commit: 3cb3091138ca0921c4569bcf7ffa062519639b6a