Date: Tue, 24 Nov 2015 18:07:39 -0800 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Adrian Chadd <adrian.chadd@gmail.com>, "Pokala, Ravi" <rpokala@panasas.com>, "freebsd-geom@freebsd.org" <freebsd-geom@freebsd.org>, "ken@freebsd.org" <ken@freebsd.org>, "scottl@freebsd.org" <scottl@freebsd.org>, "freebsd-scsi@freebsd.org" <freebsd-scsi@freebsd.org>, "imp@freebsd.org" <imp@freebsd.org> Subject: Re: Low-level trace-buffers in CAM Message-ID: <1676097.ULW1yzL7e7@ralph.baldwin.cx> In-Reply-To: <CAJ-Vmo=cfvA5k5rQt=KHpuCypHn2%2BfqYm8gBiG5eMYspBwfuNw@mail.gmail.com> References: <A760883F-317D-46C9-AD7C-B8F5D96A49DA@panasas.com> <CAJ-Vmo=cfvA5k5rQt=KHpuCypHn2%2BfqYm8gBiG5eMYspBwfuNw@mail.gmail.com>
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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
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