From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30260 invoked by alias); 5 Jul 2008 13:50:24 -0000 Received: (qmail 30252 invoked by uid 22791); 5 Jul 2008 13:50:22 -0000 X-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00,SPF_PASS X-Spam-Check-By: sourceware.org Received: from accolon.hansenpartnership.com (HELO accolon.hansenpartnership.com) (76.243.235.52) by sourceware.org (qpsmtpd/0.31) with ESMTP; Sat, 05 Jul 2008 13:49:56 +0000 Received: from localhost (localhost [127.0.0.1]) by accolon.hansenpartnership.com (Postfix) with ESMTP id 2BFC2828D; Sat, 5 Jul 2008 08:49:52 -0500 (CDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=2007; t=1215265792; bh=5rRX5ZhKFw5yV7opNop12xZHUuu/aj/fTr+lxJikfa A=; l=1368; h=Subject:From:To:Cc:In-Reply-To:References: Content-Type:Date:Message-Id:Mime-Version: Content-Transfer-Encoding; b=BLjHW/u46+gApcN5n7jgggg0tXb1HsERw1U2R zs6tPZSJ9Wquw84zclApv3gX73XgjFovj8+H/mXS6El1xNrAIeLi6J5+9Jvptf3+Z5f iIMJbb0gbIy/+9UOQu+uL+WQRBA9XVX9XC54a1T7Sm77Zr5wsBxw0tys0JIIvgqU1HE = Received: from accolon.hansenpartnership.com ([127.0.0.1]) by localhost (redscar.int.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZViJi6uKkqI5; Sat, 5 Jul 2008 08:49:50 -0500 (CDT) Received: from [153.66.150.222] (mulgrave-w.int.hansenpartnership.com [153.66.150.222]) by accolon.hansenpartnership.com (Postfix) with ESMTP id 422DA81DD; Sat, 5 Jul 2008 08:49:49 -0500 (CDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=2007; t=1215265789; bh=5rRX5ZhKFw5yV7opNop12xZHUuu/aj/fTr+lxJikfa A=; l=1368; h=Subject:From:To:Cc:In-Reply-To:References: Content-Type:Date:Message-Id:Mime-Version: Content-Transfer-Encoding; b=cMNntxNGkwUaTqLhFmIVxlPsTqLCC+pGrp0NI B3dKZ5qI6ruepdVMQW9UgE9truYR9WXE4u3XwFDR0QJ+lxj6mDDhh5Qa8NJHtTE5V6J +grDYRHBTp4jLtO1YgucYsKyr9ejbiHDvGI1WSJohcFK+SkwLqvIzrRbcKjTUDxRNS8 = Subject: Re: [Ksummit-2008-discuss] DTrace From: James Bottomley To: Christoph Hellwig Cc: Peter Zijlstra , ksummit-2008-discuss@lists.linux-foundation.org, Roland McGrath , systemtap@sources.redhat.com In-Reply-To: <20080705100536.GA18534@lst.de> References: <20080630181959.GA7988@mit.edu> <20080630192533.GE21660@redhat.com> <20080630201031.GF7988@mit.edu> <20080630204219.GA6631@redhat.com> <20080701024140.GB28143@mit.edu> <20080701070746.C6DAD15420E@magilla.localdomain> <20080701101507.GB22717@mit.edu> <20080701200632.6790A1541F5@magilla.localdomain> <20080701231327.GA5829@mit.edu> <1215251049.6320.15.camel@lappy.programming.kicks-ass.net> <20080705100536.GA18534@lst.de> Content-Type: text/plain Date: Sat, 05 Jul 2008 13:50:00 -0000 Message-Id: <1215265789.3439.8.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 (2.22.2-2.fc9) Content-Transfer-Encoding: 7bit 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 X-SW-Source: 2008-q3/txt/msg00049.txt.bz2 On Sat, 2008-07-05 at 12:05 +0200, Christoph Hellwig wrote: > On Sat, Jul 05, 2008 at 11:44:09AM +0200, Peter Zijlstra wrote: > > Also, it would be really great if you could write probes in regular C, > > some pseudo C language just messes up my mind. > > You can write probes in plain C, in fact I do this all the time. what's > missing is a nice and easy to use channel to get the traces to userspace > and interpret them, and helper for poking at kernel data structures. To be fair, you can simply "just write" entry (jprobes) and return probes (kretprobes). For the entry probes, if you want access to the function arguments you need to know the deep magic of the calling conventions of your platform (pretty easy on x86, though). However, what you can't just write are the arbitrary kprobes in file x line y because you need to know all the nasty details of dwarf to have a clue what the absolute address is and where all the local varaibles you're trying to look at are. Now ... is using systemtap to do this easier than printk? For me, yes, since a recompile reboot sequence takes quite a while, perhaps for someone with a faster machine ... For getting information back, as you know, systemtap uses relayfs. It's not the most friendly or efficient thing in the world, so I'm happy to have it wrappered by systemtap ... James