From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13966 invoked by alias); 5 Mar 2014 12:01:56 -0000 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Received: (qmail 13922 invoked by uid 89); 5 Mar 2014 12:01:55 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.2 required=5.0 tests=AWL,BAYES_00,KHOP_BIG_TO_CC,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=no version=3.3.2 X-HELO: mail9.hitachi.co.jp Received: from mail9.hitachi.co.jp (HELO mail9.hitachi.co.jp) (133.145.228.44) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 05 Mar 2014 12:01:54 +0000 Received: from mlsv6.hitachi.co.jp (unknown [133.144.234.166]) by mail9.hitachi.co.jp (Postfix) with ESMTP id 62E1E37C86; Wed, 5 Mar 2014 21:01:52 +0900 (JST) Received: from mfilter06.hitachi.co.jp by mlsv6.hitachi.co.jp (8.13.1/8.13.1) id s25C1qwP027669; Wed, 5 Mar 2014 21:01:52 +0900 Received: from vshuts04.hitachi.co.jp (vshuts04.hitachi.co.jp [10.201.6.86]) by mfilter06.hitachi.co.jp (Switch-3.3.4/Switch-3.3.4) with ESMTP id s25C1oHc022203; Wed, 5 Mar 2014 21:01:51 +0900 Received: from gxml20a.ad.clb.hitachi.co.jp (unknown [158.213.157.160]) by vshuts04.hitachi.co.jp (Postfix) with ESMTP id 7D84E14004C; Wed, 5 Mar 2014 21:01:50 +0900 (JST) Received: from ltc230.yrl.intra.hitachi.co.jp by gxml20a.ad.clb.hitachi.co.jp (Switch-3.1.10/Switch-3.1.9) id 625C11D9S00006488; Wed, 05 Mar 2014 21:01:49 +0900 Subject: [PATCH -tip v8 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: Wed, 05 Mar 2014 12:01:00 -0000 Message-ID: <20140305120144.22766.73188.stgit@ltc230.yrl.intra.hitachi.co.jp> In-Reply-To: <20140305115843.22766.8355.stgit@ltc230.yrl.intra.hitachi.co.jp> References: <20140305115843.22766.8355.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 X-IsSubscribed: yes X-SW-Source: 2014-q1/txt/msg00246.txt.bz2 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 f4233b1..1842334 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -92,6 +92,8 @@ typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip, * STUB - The ftrace_ops is just a place holder. * INITIALIZED - The ftrace_ops has already been initialized (first use time * register_ftrace_function() is called, it will initialized the ops) + * 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, @@ -103,6 +105,7 @@ enum { FTRACE_OPS_FL_RECURSION_SAFE = 1 << 6, FTRACE_OPS_FL_STUB = 1 << 7, FTRACE_OPS_FL_INITIALIZED = 1 << 8, + FTRACE_OPS_FL_SELF_FILTER = 1 << 9, }; struct ftrace_ops { 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 cd7f76d..2734f20 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4502,7 +4502,8 @@ __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();