From patchwork Thu Aug 3 12:51:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13339957 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 569E3C04A94 for ; Thu, 3 Aug 2023 12:51:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234689AbjHCMvx (ORCPT ); Thu, 3 Aug 2023 08:51:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232519AbjHCMvw (ORCPT ); Thu, 3 Aug 2023 08:51:52 -0400 Received: from mail-wm1-x34a.google.com (mail-wm1-x34a.google.com [IPv6:2a00:1450:4864:20::34a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C928110 for ; Thu, 3 Aug 2023 05:51:50 -0700 (PDT) Received: by mail-wm1-x34a.google.com with SMTP id 5b1f17b1804b1-3fd2209bde4so8512535e9.1 for ; Thu, 03 Aug 2023 05:51:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691067108; x=1691671908; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=386r6j4QMFbfOrIdvcLgjW0KP9NvXLmpvV5c26bmV8M=; b=m9ZVMP5eY+0b5z9eWP3eZHDamK+vbZ8J03CJptG9y9KX630jiL/EiWxcqk4KYB9Ixl +HeEuLS8YeL2OqVKNWYTX6QShao4xucTFdAtqe2s61kEFBgwIwXp7wCJ6zsn5Jc03soz R4vHoWcqweYalxbXx69J64Qb0V7SnChL152xScnq7pcG8WRs6pWfBAOM6P3mXJ6Oi3M1 B5a+PuIpg01BrVv7D4M+yg968ud8fgqxDxZUkEFmTJRlGWpKFgKrCjS+qlzoMKpzdyUs HTRi7UgLNxg1H7Hzj81O1BWRfuAdVzebU4svc9FPJlD+sRux8LxRUO24kGEIleafqZIt EuNQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691067108; x=1691671908; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=386r6j4QMFbfOrIdvcLgjW0KP9NvXLmpvV5c26bmV8M=; b=c9h0Vj17SWsNKTa0efXtN7KnRtSbQ2Cxpj15eEkr9FPeEuDkfhWi09ZZa3XL2rNJus XraAg9etU/4ai2yGVCFVcIj71xauXLB2h7+jX0J5WaN4yjglqUEdfXZ1XDMDxam4TVWC oTW/HNcFlfIL8VzswTkIUz8zeN7XWin7PQEmFzJWBaW9yN7HP3jwvTotZ+5ga29Of/Bq lNSeXwWT+RJcLsqe4dQPyQk6qxIErsNkF1ZZxTFbau8A/LngrAzZnHPOEfFhxtyTxQLH mjJ0VnpfcAjyd5nb7qFMzBzPsRJ1lMRgBeFaVcki0Tz6noJUhA8FMO+SYijRbzb6BGgv kTWQ== X-Gm-Message-State: ABy/qLbqonDvdo4peQ2ubyLfEF7LHNbv6RJT6zUMdN3cY0S0MAvivU2J bne5Q6Ls/DSwAK9b4tgd2VjDFKvp1KXmQ3et X-Google-Smtp-Source: APBJJlEMCWM5NeRkHmGQry3+/bOgGmpHiP0VNvs210IGDy1wU9DxkGtBcvjjlQX6+zmh8gXkqO9az/JjiJ+Hl4vH X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:adf:f20a:0:b0:314:1ac7:2763 with SMTP id p10-20020adff20a000000b003141ac72763mr52577wro.0.1691067108515; Thu, 03 Aug 2023 05:51:48 -0700 (PDT) Date: Thu, 3 Aug 2023 13:51:35 +0100 Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.585.gd2178a4bd4-goog Message-ID: <20230803125137.1779474-1-vdonnefort@google.com> Subject: [PATCH v6 0/2] 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: kernel-team@android.com, Vincent Donnefort Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org 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 access to userspace to the ring-buffer pages directly via a mapping. A piece of software can now become a reader of the ring-buffer, and drive a consuming or non-consuming read in a similar fashion to what trace and trace_pipe offer. Attached to this cover letter an example of consuming read for a ring-buffer, using libtracefs. Vincent 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 | 326 +++++++++++++++++++++++++++++++- kernel/trace/trace.c | 82 +++++++- 4 files changed, 440 insertions(+), 6 deletions(-) create mode 100644 include/uapi/linux/trace_mmap.h base-commit: 626c67169f9972fffcdf3bc3864de421f162ebf5