From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [RFC PATCH v3 1/5] irq: add tracepoint to softirq_raise Date: Wed, 21 Jul 2010 22:01:34 +0900 (JST) Message-ID: <20100721215836.86F9.A69D9226@jp.fujitsu.com> References: <4C469A41.4020807@jp.fujitsu.com> <20100721111419.GB21259@hmsreliant.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Cc: kosaki.motohiro@jp.fujitsu.com, Koki Sanagi , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, kaneshige.kenji@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, laijs@cn.fujitsu.com, scott.a.mcmillan@intel.com, rostedt@goodmis.org, eric.dumazet@gmail.com, fweisbec@gmail.com, mathieu.desnoyers@polymtl.ca To: Neil Horman Return-path: Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:49647 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753336Ab0GUNBi (ORCPT ); Wed, 21 Jul 2010 09:01:38 -0400 In-Reply-To: <20100721111419.GB21259@hmsreliant.think-freely.org> Sender: netdev-owner@vger.kernel.org List-ID: > > >> #endif /* _TRACE_IRQ_H */ > > >> diff --git a/kernel/softirq.c b/kernel/softirq.c > > >> index 825e112..6790599 100644 > > >> --- a/kernel/softirq.c > > >> +++ b/kernel/softirq.c > > >> @@ -215,9 +215,9 @@ restart: > > >> int prev_count = preempt_count(); > > >> kstat_incr_softirqs_this_cpu(h - softirq_vec); > > >> > > >> - trace_softirq_entry(h, softirq_vec); > > >> + trace_softirq_entry(h - softirq_vec); > > >> h->action(h); > > >> - trace_softirq_exit(h, softirq_vec); > > >> + trace_softirq_exit(h - softirq_vec); > > > > > > You're loosing information here by reducing the numbers of parameters in this > > > tracepoint. How many other tracepoint scripts rely on having both pointers > > > handy? Why not just do the pointer math inside your tracehook instead? > > > > In __raise_softirq_irqoff macro there is no method to refer softirq_vec, so it > > can't use softirq DECLARE_EVENT_CLASS as is. > > Currently, there is no script using softirq_entry or softirq_exit. > > > That shouldn't matter, just pass in NULL for softirq_vec in > __raise_softirq_irqoff as the second argument to the trace function. You may > need to fix up the class definition so that the assignment or printk doesn't try > to dereference that pointer when its NULL, but thats easy enough, and it avoids > breaking any other perf scripts floating out there. please see 5 lines above. we already have 'h - softirq_vec' calculation in this function. so, Sanagi-san's change don't makes any overhead. So, if the overhead is zero, I'd prefer simplest tracepoint definition :)