From patchwork Mon Jan 9 13:58:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 640725 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 C7227C678D5 for ; Mon, 9 Jan 2023 13:58:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234085AbjAIN6y (ORCPT ); Mon, 9 Jan 2023 08:58:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237225AbjAIN6i (ORCPT ); Mon, 9 Jan 2023 08:58:38 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D109F25CD; Mon, 9 Jan 2023 05:58:37 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 80ABAAD7; Mon, 9 Jan 2023 05:59:19 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A9AB63F23F; Mon, 9 Jan 2023 05:58:35 -0800 (PST) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com, lenb@kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, mhiramat@kernel.org, ndesaulniers@google.com, ojeda@kernel.org, peterz@infradead.org, rafael.j.wysocki@intel.com, revest@chromium.org, robert.moore@intel.com, rostedt@goodmis.org, will@kernel.org Subject: [PATCH 0/8] arm64/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS Date: Mon, 9 Jan 2023 13:58:20 +0000 Message-Id: <20230109135828.879136-1-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org This series adds a new DYNAMIC_FTRACE_WITH_CALL_OPS mechanism, and enables support for this on arm64. This significantly reduces the overhead of tracing when a callsite/tracee has a single associated tracer, avoids a number of issues that make it undesireably and infeasible to use dynamically-allocated trampolines (e.g. branch range limitations), and makes it possible to implement support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS in future. The main idea is to give each ftrace callsite an associated pointer to an ftrace_ops. The architecture's ftrace_caller trampoline can recover the ops pointer and invoke ops->func from this without needing to use ftrace_ops_list_func, which has to iterate through all registered ops. To do this, we use -fpatchable-function-entry=M,N, there N NOPs are placed before the function entry point. On arm64 NOPs are always 4 bytes, so by allocating 2 per-function NOPs, we have enaough space to place a 64-bit value. So that we can manipulate the pointer atomically, we need to align instrumented functions to at least 8 bytes. The first three patches enable this function alignment, requiring changes to the ACPICA Makefile, and working around cases where GCC drops alignment. The final four patches implement support for arm64. As noted in the final patch, this results in a significant reduction in overhead: Before this patch: Number of tracers || Total time | Per-call average time (ns) Relevant | Irrelevant || (ns) | Total | Overhead =========+============++=============+==============+============ 0 | 0 || 94,583 | 0.95 | - 0 | 1 || 93,709 | 0.94 | - 0 | 2 || 93,666 | 0.94 | - 0 | 10 || 93,709 | 0.94 | - 0 | 100 || 93,792 | 0.94 | - ---------+------------++-------------+--------------+------------ 1 | 1 || 6,467,833 | 64.68 | 63.73 1 | 2 || 7,509,708 | 75.10 | 74.15 1 | 10 || 23,786,792 | 237.87 | 236.92 1 | 100 || 106,432,500 | 1,064.43 | 1063.38 ---------+------------++-------------+--------------+------------ 1 | 0 || 1,431,875 | 14.32 | 13.37 2 | 0 || 6,456,334 | 64.56 | 63.62 10 | 0 || 22,717,000 | 227.17 | 226.22 100 | 0 || 103,293,667 | 1032.94 | 1031.99 ---------+------------++-------------+--------------+-------------- Note: per-call overhead is estiamated relative to the baseline case with 0 relevant tracers and 0 irrelevant tracers. After this patch Number of tracers || Total time | Per-call average time (ns) Relevant | Irrelevant || (ns) | Total | Overhead =========+============++=============+==============+============ 0 | 0 || 94,541 | 0.95 | - 0 | 1 || 93,666 | 0.94 | - 0 | 2 || 93,709 | 0.94 | - 0 | 10 || 93,667 | 0.94 | - 0 | 100 || 93,792 | 0.94 | - ---------+------------++-------------+--------------+------------ 1 | 1 || 281,000 | 2.81 | 1.86 1 | 2 || 281,042 | 2.81 | 1.87 1 | 10 || 280,958 | 2.81 | 1.86 1 | 100 || 281,250 | 2.81 | 1.87 ---------+------------++-------------+--------------+------------ 1 | 0 || 280,959 | 2.81 | 1.86 2 | 0 || 6,502,708 | 65.03 | 64.08 10 | 0 || 18,681,209 | 186.81 | 185.87 100 | 0 || 103,550,458 | 1,035.50 | 1034.56 ---------+------------++-------------+--------------+------------ Note: per-call overhead is estiamated relative to the baseline case with 0 relevant tracers and 0 irrelevant tracers. Thanks, Mark. Mark Rutland (8): Compiler attributes: GCC function alignment workarounds ACPI: Don't build ACPICA with '-Os' arm64: Extend support for CONFIG_FUNCTION_ALIGNMENT ftrace: Add DYNAMIC_FTRACE_WITH_CALL_OPS arm64: insn: Add helpers for BTI arm64: patching: Add aarch64_insn_write_literal_u64() arm64: ftrace: Update stale comment arm64: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS arch/arm64/Kconfig | 3 + arch/arm64/Makefile | 5 +- arch/arm64/include/asm/ftrace.h | 15 +-- arch/arm64/include/asm/insn.h | 1 + arch/arm64/include/asm/linkage.h | 10 +- arch/arm64/include/asm/patching.h | 2 + arch/arm64/kernel/asm-offsets.c | 4 + arch/arm64/kernel/entry-ftrace.S | 32 +++++- arch/arm64/kernel/ftrace.c | 158 +++++++++++++++++++++++++++- arch/arm64/kernel/patching.c | 17 +++ drivers/acpi/acpica/Makefile | 2 +- include/linux/compiler_attributes.h | 23 +++- include/linux/ftrace.h | 15 ++- kernel/trace/Kconfig | 7 ++ kernel/trace/ftrace.c | 109 ++++++++++++++++++- 15 files changed, 371 insertions(+), 32 deletions(-)