Date: Tue, 5 Jun 2012 16:20:00 +0100 From: Attilio Rao <attilio@freebsd.org> To: =?UTF-8?Q?Dag=2DErling_Sm=C3=B8rgrav?= <des@des.no> Cc: arch@freebsd.org Subject: Re: KTR_SPAREx Message-ID: <CAJ-FndAadYbqiWUTupXLEcRMkYYL50Ssehi8f8vv6YXvQzy4OA@mail.gmail.com> In-Reply-To: <CAJ-FndAMsoB1RAyS-Pa1JCv7W0qsviRxtShZ3uk_Tpd%2BJ_EBaQ@mail.gmail.com> References: <86bokyvtc2.fsf@ds4.des.no> <CAJ-FndAMsoB1RAyS-Pa1JCv7W0qsviRxtShZ3uk_Tpd%2BJ_EBaQ@mail.gmail.com>
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2012/6/5 Attilio Rao <attilio@freebsd.org>: > 2012/6/5 Dag-Erling Sm=C3=B8rgrav <des@des.no>: >> While working on Capsicum last year, I noticed that some of the spare >> KTR types are (ab)used for different purposes by different parts of the >> code. =C2=A0KTR_SPARE[234] are all documented as "/* XXX Used by cxgb */= ", >> but KTR_SPARE3, for instance, is widely used for clock events. =C2=A0Her= e is >> a complete list: > > The truth is, KTR is thought to be a mechanism for catering > "on-the-fly" the tracing of the events, but the very limited > mask/classes of events it provides makes this completely useless. > I don't recall a case where I had to not patch manually KTR knobs to > do actual debugging. > > What I really would like to see is: > - Of course remove the bogus usage of KTR_SPAREX in the drivers > - Make the mask of events much bigger than the current one > - Enlarge the number of KTR_SPARE available (16 would be ok) > - By default have KTR_SPARE0-15 to be on in the kernel along with KTR > option, or maybe when the kernel is still in the debugging phase (but > leave in a knob for disabling it) > - Use the dynamic masking system to just mask the SPARE you are > interested into. This way your driver can simply use a KTR_SPARE for > development and you will mask out the right one at run time. Forgot to mention, even if this is mostly unrelated to your point: we should make a better job of breaking further the current set of KTR classes on a per-subsystem basis. KTR_VFS or KTR_VM (and others) are far too large right now. Attilio --=20 Peace can only be achieved by understanding - A. Einstein
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