From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760298AbZBXRj2 (ORCPT ); Tue, 24 Feb 2009 12:39:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757319AbZBXRjP (ORCPT ); Tue, 24 Feb 2009 12:39:15 -0500 Received: from nf-out-0910.google.com ([64.233.182.188]:5795 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760189AbZBXRjO (ORCPT ); Tue, 24 Feb 2009 12:39:14 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=wBGo3tIU5u+iryZJIfHF48PaYlyXA7DsXY2M443lwZc389DZ7IAwe+4QB85nC4/w/R CGJ/ptTlkyhRmoYOCzohlp9RVgUvaoI8+gwKE5PYCqSJYIKxVPpNyQPdh1t0oeHcLubt YVWt1K+QboEMKUTawk1SHMeMVSdTiBlMvDPpc= Date: Tue, 24 Feb 2009 18:39:09 +0100 From: Frederic Weisbecker To: Ingo Molnar Cc: Jason Baron , linux-kernel@vger.kernel.org, Steven Rostedt , Lai Jiangshan , Peter Zijlstra , Arnaldo Carvalho de Melo Subject: Re: [PATCH 0/3] tracing/ftrace: ftrace_bprintk Message-ID: <20090224173908.GF5765@nowhere> References: <20090224051618.GA5142@nowhere> <20090224171718.GA3189@redhat.com> <20090224172530.GD14553@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090224172530.GD14553@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 24, 2009 at 06:25:30PM +0100, Ingo Molnar wrote: > > * Jason Baron wrote: > > > On Tue, Feb 24, 2009 at 06:16:18AM +0100, Frederic Weisbecker wrote: > > > Hi, > > > > > > These three patches are part of a patchset posted by Lai Jiangshan in december 2008. > > > They introduce a binary version of ftrace_printk() called ftrace_bprintk() > > > > > > While having the same goal: print a generic message entry into the ring buffer, > > > their approaches are very different. > > > > > > - ftrace_printk() does the formatting job on tracing time, insert the whole resulting string > > > into the ring buffer, and then the string is printed on output time without a lot of modifications. > > > > > > - ftrace_bprintk() does no formatting on tracing time. Instead, it looks at the format string > > > to find the types and the numbers of the arguments and directly stores them as-is into the > > > ring-buffer. Then the format string is stored into the ring-buffer too, but only by its address, > > > it is not copied. Then on output time only, the final string is formatted and sent to the user. > > > This gives a result about as fast as a traditional tracer with fixed fields types, except that > > > we can print random types and numbers of fields here. > > > > > > > > > The first patch adds the generic support for binary formatting. > > > The second adds the support for binary print types on ftrace > > > and the last introduces ftrace_bprintk() which supports safely the modules > > > by listening on the module loading/unloading notifier to keep track of > > > unwanted freed format strings. > > > > > > Lai Jiangshan (3): > > > add binary printf > > > ftrace: infrastructure for supporting binary record > > > ftrace: add ftrace_bprintk() > > > > > > > hi, > > > > this seems like a really valuable feature....I'm just > > wondering about a couple of things.... > > > > If the 'brpintk tracer' in trace/trace_bprintk.c is just being > > used to set an enabled flag for printing out these binary > > records, then are we better off with just an option flag in > > the 'trace_options' file? > > > > Second, can we somehow combine ftrace_printk() and > > ftrace_bprintk(), so that a developer can just use one > > interface? Perhaps, ftrace_printk calls ftrace_bprintk if > > binary option flag is set, otherwise, it just outputs things > > normally. > > Well, ftrace_bprintk() seems to be a worthy and transparent > replacement for ftrace_printk() to me. I.e. lets just use this > as the new implementation for ftrace_printk(). > > Would there be any downsides of doing so? I dont see any. > > Ingo That's what I think too. For now I posted Lai's patchset, but my purpose is to replace the old ftrace_printk by this new one. Once it is merged on -tip I'll start iterating around to improve it and replace ftrace_printk. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/