Date: Wed, 25 Nov 2015 23:18:37 +0000 From: "Pokala, Ravi" <rpokala@panasas.com> To: John Baldwin <jhb@freebsd.org>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Cc: Adrian Chadd <adrian.chadd@gmail.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: <4C8D47C3-CA6C-46DA-A318-98E114B2A506@panasas.com> In-Reply-To: <1676097.ULW1yzL7e7@ralph.baldwin.cx> References: <A760883F-317D-46C9-AD7C-B8F5D96A49DA@panasas.com> <CAJ-Vmo=cfvA5k5rQt=KHpuCypHn2%2BfqYm8gBiG5eMYspBwfuNw@mail.gmail.com> <1676097.ULW1yzL7e7@ralph.baldwin.cx>
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-----Original Message----- From: John Baldwin <jhb@freebsd.org> Date: 2015-11-24, Tuesday at 18:07 To: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Cc: Adrian Chadd <adrian.chadd@gmail.com>, Ravi Pokala <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 >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) Wait, you're talking about using Berkeley Packet Filter in the context of storage command tracing? That's giving me a major parse error... -Ravi >-- >John Baldwin
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