From owner-freebsd-hackers@freebsd.org Thu Nov 26 03:28:16 2015 Return-Path: Delivered-To: freebsd-hackers@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 7EDB2A37519; Thu, 26 Nov 2015 03:28:16 +0000 (UTC) (envelope-from julian@freebsd.org) Received: from vps1.elischer.org (vps1.elischer.org [204.109.63.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 539AE1498; Thu, 26 Nov 2015 03:28:15 +0000 (UTC) (envelope-from julian@freebsd.org) Received: from Julian-MBP3.local (ppp121-45-251-140.lns20.per4.internode.on.net [121.45.251.140]) (authenticated bits=0) by vps1.elischer.org (8.15.2/8.15.2) with ESMTPSA id tAQ3RxZL074102 (version=TLSv1.2 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 25 Nov 2015 19:28:02 -0800 (PST) (envelope-from julian@freebsd.org) Subject: Re: Low-level trace-buffers in CAM To: John Baldwin , freebsd-hackers@freebsd.org References: <1676097.ULW1yzL7e7@ralph.baldwin.cx> Cc: Adrian Chadd , "freebsd-geom@freebsd.org" , "ken@freebsd.org" , "Pokala, Ravi" , "scottl@freebsd.org" , "freebsd-scsi@freebsd.org" , "imp@freebsd.org" From: Julian Elischer Message-ID: <56567C39.6050002@freebsd.org> Date: Thu, 26 Nov 2015 11:27:53 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1676097.ULW1yzL7e7@ralph.baldwin.cx> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Nov 2015 03:28:16 -0000 On 25/11/2015 10:07 AM, John Baldwin wrote: > On Monday, October 26, 2015 09:52:25 PM Adrian Chadd wrote: >> Hi, >> >> ok. So this is where I create work for people. :-) >> >> Something I've been tossing up for quite some time is a generic >> version of this that exposes a ring-buffer of entries back to >> userland. For things like this, things like ALQ/KTR, etc, it's all >> just a producer-consumer ring based thing. You don't even care about >> multiple readers; that's a userland thing. >> >> So, I'm a big fan of this. I did this for the ath driver to debug >> descriptors and register accesses and it was a big help. I'd really >> like to see a more generic way we can expose this data in an efficient >> manner! > I actually think bpf might not be a bad interface (as I suggested at > the vendor summit), though I think we need a way to enumerate BPF taps > that aren't network interfaces (if we fix this then we can remove the > fake USB ifnets and make glebius@ happy as well). Then you can look > at these things in wireshark (which would be a bit bizarre perhaps) I disagree. the advent of iSCSI makes this a natural thing. I would be very surprised if there were not already patches for wireshark to interpret scsi command blocks. I agree with you on this, it is a very logical way to do it. We may need to define a new form of interface for it but it makes perfect sense.