linux-kernel - Re: [RFC 1/2] kernel patch for dump user space stack tool

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Message-ID: <1334914719.2463.32.camel@laptop>
Date:	Fri, 20 Apr 2012 11:38:39 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	"Tu, Xiaobing" <xiaobing.tu@...el.com>,
	Lin Ming <mlin@...pku.edu.cn>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"Zuo, Jiao" <jiao.zuo@...el.com>
Subject: Re: [RFC 1/2] kernel patch for dump user space stack tool

On Thu, 2012-04-19 at 13:17 +0800, Yanmin Zhang wrote:
> Although not checking the source codes of pstack (sorry, I'm busy in debugging
> many critical issues), I think pstack is based on ptrace interface, which means:
> 1) It need traps into system for many times to collect call frames of one
> task.
> 2) It need send signal to the ptraced process to stop it. Such behavior
> might have some impact if the ptraced process also processes many signals.

Yeah, but who cares.. its debugging stuff..

> 3) The data parsing to get symbols might not be split from data collection.
> I mean, it collects call frames of one process, then parses it; then collects the 2nd
> task's. If there are many processes, it couldn't collect the data just at the monitor
> time point. 

This is equally true for your silly patch.

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