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[2620:137:e000::1:20]) by mx.google.com with ESMTP id fr1-20020a17090ae2c100b002680f00f8f3si3016219pjb.17.2023.08.03.06.27.53; Thu, 03 Aug 2023 06:28:07 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20221208 header.b=m9ZVMP5e; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234346AbjHCMvy (ORCPT + 99 others); Thu, 3 Aug 2023 08:51:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232648AbjHCMvw (ORCPT ); Thu, 3 Aug 2023 08:51:52 -0400 Received: from mail-wr1-x449.google.com (mail-wr1-x449.google.com [IPv6:2a00:1450:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C9E43588 for ; Thu, 3 Aug 2023 05:51:50 -0700 (PDT) Received: by mail-wr1-x449.google.com with SMTP id ffacd0b85a97d-31400956ce8so668182f8f.3 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=iBh3AwY3tLw+z2ScS1mFvR0XDcjo1YKtRFvwSCU+MCBfox479f2EcKuDn6Ejd99Yob VsvsS4L1MgPQaKGRT1kjBm5RwPQDtV+MZkQXVrvvXxMLqlaMuCAUpZemIkl35fiEqiDC esZVbwMOO/wY6wFRL8nysytO3S+nPxVSlNn6gKeW6tWiiXW9O9zoEo5NqL0r94PA+vwE zrZa19qz1JnUOdNNT5EEzUlq6X10Ae9qaVOmB2BemcIozULBKl2LCsIw72WWUEmkObT2 5/RCXJIauDUz4y4Bhui9CeykkhO/AdZkbLbKnc5d23AhuMA7XbGLERF5QYMGBj4W8uFE YhuQ== X-Gm-Message-State: ABy/qLae5C+gKw8T1p5NYY5WQGAh9SV5GasG9gJNCkGj7HS93sKgJlWk OPf881Z/iOo+tZjiK5w0l7b7/rZvWzwqPO0D 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 X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1773214669475352843 X-GMAIL-MSGID: 1773214669475352843 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