From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756275AbaDQITv (ORCPT ); Thu, 17 Apr 2014 04:19:51 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:41335 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751025AbaDQITq (ORCPT ); Thu, 17 Apr 2014 04:19:46 -0400 Subject: [PATCH -tip v9 26/26] ftrace: Introduce FTRACE_OPS_FL_SELF_FILTER for ftrace-kprobe From: Masami Hiramatsu To: linux-kernel@vger.kernel.org, Ingo Molnar Cc: Andi Kleen , Ananth N Mavinakayanahalli , Sandeepa Prabhu , Frederic Weisbecker , x86@kernel.org, Steven Rostedt , fche@redhat.com, mingo@redhat.com, systemtap@sourceware.org, "H. Peter Anvin" , Thomas Gleixner Date: Thu, 17 Apr 2014 17:19:38 +0900 Message-ID: <20140417081937.26341.73274.stgit@ltc230.yrl.intra.hitachi.co.jp> In-Reply-To: <20140417081636.26341.87858.stgit@ltc230.yrl.intra.hitachi.co.jp> References: <20140417081636.26341.87858.stgit@ltc230.yrl.intra.hitachi.co.jp> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since the kprobes itself owns a hash table to get a kprobe data structure corresponding to the given ip address, there is no need to test ftrace hash in ftrace side. To achive better performance on ftrace-based kprobe, FTRACE_OPS_FL_SELF_FILTER flag to ftrace_ops which means that ftrace skips testing its own hash table. Without this patch, ftrace_lookup_ip() is biggest cycles consumer when 20,000 kprobes are enabled. ---- Samples: 1K of event 'cycles', Event count (approx.): 340068894 + 20.77% [k] ftrace_lookup_ip + 8.33% [k] kprobe_trace_func + 4.83% [k] get_kprobe_cached ---- With this patch, ftrace_lookup_ip() vanished from the cycles consumer list (of course, there is no caller on hotpath anymore :)) ---- Samples: 1K of event 'cycles', Event count (approx.): 186861492 + 9.95% [k] kprobe_trace_func + 6.00% [k] kprobe_ftrace_handler + 5.53% [k] get_kprobe_cached ---- Changes from v7: - Re-evaluate the performance improvement. Signed-off-by: Masami Hiramatsu Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: Ingo Molnar --- include/linux/ftrace.h | 3 +++ kernel/kprobes.c | 2 +- kernel/trace/ftrace.c | 3 ++- 3 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 9212b01..36e4cb5 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -93,6 +93,8 @@ typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip, * INITIALIZED - The ftrace_ops has already been initialized (first use time * register_ftrace_function() is called, it will initialized the ops) * DELETED - The ops are being deleted, do not let them be registered again. + * SELF_FILTER - The ftrace_ops function filters ip by itself. Do not need to + * check hash table on each hit. */ enum { FTRACE_OPS_FL_ENABLED = 1 << 0, @@ -105,6 +107,7 @@ enum { FTRACE_OPS_FL_STUB = 1 << 7, FTRACE_OPS_FL_INITIALIZED = 1 << 8, FTRACE_OPS_FL_DELETED = 1 << 9, + FTRACE_OPS_FL_SELF_FILTER = 1 << 10, }; /* diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 465e912..af1ff6a 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1020,7 +1020,7 @@ static struct kprobe *alloc_aggr_kprobe(struct kprobe *p) #ifdef CONFIG_KPROBES_ON_FTRACE static struct ftrace_ops kprobe_ftrace_ops __read_mostly = { .func = kprobe_ftrace_handler, - .flags = FTRACE_OPS_FL_SAVE_REGS, + .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_SELF_FILTER, }; static int kprobe_ftrace_enabled; diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 1fd4b94..4235851 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4520,7 +4520,8 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, */ preempt_disable_notrace(); do_for_each_ftrace_op(op, ftrace_ops_list) { - if (ftrace_ops_test(op, ip, regs)) + if (op->flags & FTRACE_OPS_FL_SELF_FILTER || + ftrace_ops_test(op, ip, regs)) op->func(ip, parent_ip, op, regs); } while_for_each_ftrace_op(op); preempt_enable_notrace();