From owner-svn-src-head@freebsd.org Thu Jan 21 00:16:03 2016 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id CB773A8AA33; Thu, 21 Jan 2016 00:16:03 +0000 (UTC) (envelope-from rpokala@mac.com) Received: from mr11p00im-asmtp002.me.com (mr11p00im-asmtp002.me.com [17.110.69.253]) (using TLSv1.2 with cipher DHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id AE34C1151; Thu, 21 Jan 2016 00:16:03 +0000 (UTC) (envelope-from rpokala@mac.com) Received: from [172.17.133.77] (dip-cali.panasas.com [64.80.217.3]) by mr11p00im-asmtp002.me.com (Oracle Communications Messaging Server 7.0.5.36.0 64bit (built Sep 8 2015)) with ESMTPSA id <0O1A004G20QJ3G10@mr11p00im-asmtp002.me.com>; Thu, 21 Jan 2016 00:15:57 +0000 (GMT) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-01-20_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 clxscore=1011 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1510270003 definitions=main-1601210003 User-Agent: Microsoft-MacOutlook/0.0.0.160109 Date: Wed, 20 Jan 2016 16:15:54 -0800 Subject: Re: svn commit: r294471 - head/sys/dev/usb/wlan From: Ravi Pokala Sender: "Pokala, Ravi" To: Adrian Chadd , Andriy Voskoboinyk Cc: "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" Message-id: <4FBE9133-AB30-4D30-A298-1742952700C5@panasas.com> Thread-topic: svn commit: r294471 - head/sys/dev/usb/wlan References: <201601202327.u0KNR2Hh066219@repo.freebsd.org> In-reply-to: MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 7bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 21 Jan 2016 00:16:03 -0000 -----Original Message----- From: on behalf of Adrian Chadd Date: 2016-01-20, Wednesday at 16:02 To: Andriy Voskoboinyk Cc: "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" Subject: Re: svn commit: r294471 - head/sys/dev/usb/wlan >Hi, > >So yeah, I think it's time we just bit the bullet and wrote a >generic-ish debug/ktr framework for drivers to use so drivers and >infrastructure doesn't keep spinning its own damned debugging stuff. > >(I know people keep saying "dtrace", but ...) > >Let's have a think about it. One issue I have with DTrace (and KTR, though I'm even less familiar with it than I am with DTrace) is that you only get a stream of what's happening right now - there's no way to see *what just happened*. For example, I wrote an ATA command tracing infrastructure for Panasas which keeps the last several thousand commands in a trace buffer, and a tool that extracts the buffer and saves it to a file. We can then feed that file into various analysis tools, which can show us exactly what we sent to the drive, and exactly what the drive sent back to us. (The nice thing is, the buffer is also in the vmcore, so we can easily extract it after a panic, and it's identical to what you get from the live system, so the same analysis tools can be used in both instances.) This has come in very handy when we want to see, for example, what new and stupid thing a drive did that caused an error, slowdown or panic. -Ravi (rpokala@) >-a