From: firstname.lastname@example.org To: "Ville Syrjälä" <email@example.com> Cc: firstname.lastname@example.org, LKML <email@example.com>, David Airlie <firstname.lastname@example.org>, Jason Baron <email@example.com>, Thomas Zimmermann <firstname.lastname@example.org> Subject: Re: [RFC PATCH 1/2] drm: RFC add choice to use dynamic debug in drm-debug Date: Fri, 4 Dec 2020 12:20:21 -0700 [thread overview] Message-ID: <CAJfuBxysOxnm846u71f0rQCH9NX-7AMe4brmiD0vqfGeQKuVOw@mail.gmail.com> (raw) In-Reply-To: <X8pY/H512EMR3bUX@intel.com> On Fri, Dec 4, 2020 at 8:42 AM Ville Syrjälä <email@example.com> wrote: > > On Thu, Dec 03, 2020 at 08:53:17PM -0700, Jim Cromie wrote: > > drm's debug system uses distinct categories of debug messages, mapped > > to bits in drm.debug. Currently, code does a lot of unlikely bit-mask > > checks on drm.debug (in drm_debug_enabled), we can use dynamic debug > > instead, and get all that jump_label goodness. > > whatis jump_label? Sorry, I should have at least capitalized that, and spelled it differently kernel/Makefile 118:obj-$(CONFIG_JUMP_LABEL) += jump_label.o it is the hot-patching substrate underneath it all. static-key, static-call, etc? dynamic-debug uses static-key directly. > > One thing that bugs me about the current drm_dbg() stuff is that > it's a function, and thus we pay the cost of setting up the > arguments even when debugs are not enabled. I played around a bit > with making it a macro again with the unlikely bit check moved > into the macro. That did seem to make some of the asm a bit nicer > where the debug stuff got shoved out the main codepath, but > it did result in a slight net increase in code size. What I didn't > have time to do is check if this has any measurable speed effect > on eg. TEST_ONLY commits. > > And while doing that I started to ponder if we could use something > like the alternate() instruction stuff to patch the code at runtime > in order to turn all those debug checks into nops when debugging > is not enabled. But I couldn't immediately find any generic > infrastructure for it. So now I wonder if this jump_label is something > like that? > this is the droid youre looking for ;-) > > > -- > Ville Syrjälä > Intel
next prev parent reply other threads:[~2020-12-04 19:21 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-04 3:53 [RFC PATCH 0/2] drm: use dynamic_debug Jim Cromie 2020-12-04 3:53 ` [RFC PATCH 1/2] drm: RFC add choice to use dynamic debug in drm-debug Jim Cromie 2020-12-04 15:42 ` Ville Syrjälä 2020-12-04 19:20 ` jim.cromie [this message] 2020-12-11 15:30 ` Ville Syrjälä 2020-12-17 21:31 ` jim.cromie 2020-12-04 3:53 ` [RFC PATCH 2/2] i915: POC use dynamic_debug_exec_queries to control pr_debugs in gvt Jim Cromie
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