From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754023AbaEHK7x (ORCPT ); Thu, 8 May 2014 06:59:53 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:22471 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753903AbaEHK7w (ORCPT ); Thu, 8 May 2014 06:59:52 -0400 Date: Thu, 8 May 2014 06:59:47 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andi Kleen , Ananth N Mavinakayanahalli , Sandeepa Prabhu , Frederic Weisbecker , x86@kernel.org, fche@redhat.com, mingo@redhat.com, systemtap@sourceware.org, "H. Peter Anvin" , Thomas Gleixner Subject: Re: [PATCH -tip v10 7/7] ftrace: Introduce FTRACE_OPS_FL_SELF_FILTER for ftrace-kprobe Message-ID: <20140508065947.214f4951@gandalf.local.home> In-Reply-To: <20140508093930.31767.86419.stgit@ltc230.yrl.intra.hitachi.co.jp> References: <20140508093842.31767.43766.stgit@ltc230.yrl.intra.hitachi.co.jp> <20140508093930.31767.86419.stgit@ltc230.yrl.intra.hitachi.co.jp> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 08 May 2014 18:39:30 +0900 Masami Hiramatsu wrote: > 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 I should look at your filtering methods, maybe it can make ftrace filtering better? > ---- > > 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 ae9504b..f1fa7d27 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. - The ftrace_ops function has its own ip filter and does not need to rely on the ftrace internal ip filtering. > */ > 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 0f5f23c..5c6e410 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1027,7 +1027,7 @@ 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 4a54a25..062ca20 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -4501,7 +4501,8 @@ __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)) Hmm, I wonder if I should add the check for: !(op->flags & FTRACE_OPS_FL_STUB) here too? But that's another change that I'll do. Just update the flag description as I commented and the rest looks good. -- Steve > op->func(ip, parent_ip, op, regs); > } while_for_each_ftrace_op(op); > preempt_enable_notrace(); >