From owner-freebsd-hackers@freebsd.org Wed Nov 25 02:27:05 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 DB060A37F1F; Wed, 25 Nov 2015 02:27:05 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id B5EF01097; Wed, 25 Nov 2015 02:27:05 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from ralph.baldwin.cx (c-73-231-226-104.hsd1.ca.comcast.net [73.231.226.104]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id C7840B95B; Tue, 24 Nov 2015 21:27:04 -0500 (EST) From: John Baldwin To: freebsd-hackers@freebsd.org Cc: Adrian Chadd , "Pokala, Ravi" , "freebsd-geom@freebsd.org" , "ken@freebsd.org" , "scottl@freebsd.org" , "freebsd-scsi@freebsd.org" , "imp@freebsd.org" Subject: Re: Low-level trace-buffers in CAM Date: Tue, 24 Nov 2015 18:07:39 -0800 Message-ID: <1676097.ULW1yzL7e7@ralph.baldwin.cx> User-Agent: KMail/4.14.3 (FreeBSD/10.2-STABLE; KDE/4.14.3; amd64; ; ) In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Tue, 24 Nov 2015 21:27:04 -0500 (EST) 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: Wed, 25 Nov 2015 02:27:06 -0000 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) -- John Baldwin