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[98.38.17.99]) by smtp.googlemail.com with ESMTPSA id 586e51a60fabf-41cc7760c08sm3075171fac.4.2026.03.26.11.55.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2026 11:55:35 -0700 (PDT) From: Jim Cromie To: linux-kernel@vger.kernel.org, airlied@gmail.com, simona@ffwll.ch, jbaron@akamai.com, gregkh@linuxfoundation.org Cc: jim.cromie@gmail.com, mripard@kernel.org, tzimmermann@suse.de, maarten.lankhorst@linux.intel.com, jani.nikula@intel.com, ville.syrjala@linux.intel.com, christian.koenig@amd.com, matthew.auld@intel.com, arunpravin.paneerselvam@amd.com, louis.chauvet@bootlin.com, skhan@linuxfoundation.org, pmladek@suse.com, ukaszb@chromium.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, amd-gfx@lists.freedesktop.org Subject: [PATCH v12 41/69] drm_vblank: avoid bit-test when DRM_USE_DYNAMIC_DEBUG=y Date: Thu, 26 Mar 2026 12:53:45 -0600 Message-ID: <20260326185413.1205870-42-jim.cromie@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260326185413.1205870-1-jim.cromie@gmail.com> References: <20260326185413.1205870-1-jim.cromie@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" drm_crtc_vblank_helper_get_vblank_timestamp_internal() is called about ~100 times per sec, on a single display. It currently calls drm_debug_enabled(DRM_UT_VBL) to avoid doing ktime_to_timespec64() conversions when drm_dbg_vbl() is disabled. When CONFIG_DRM_USE_DYNAMIC_DEBUG=3DY, that bit-test is redundant, because its also done by the static-key inside drm_dbg_vbl(). In this case, we can move the ktime conversions into the drm_dbg_vbl() argument list (using a comma operator to evaluate the assignment, then pass the address of its LHS). Then the __dynamic_func_call() wrapping the func guards the arg-list too, avoiding its evaluation when its not being printed. When CONFIG_DRM_USE_DYNAMIC_DEBUG=3DN, the bit-test is needed, because the conversion in the arg-list is not guarded, and we'd do the conversions even when the callsite is disabled. We can optimize for both Y/N cases by changing drm_debug_enabled(DRM_UT_VBL) to __drm_debug_enabled(DRM_UT_VBL). This gives us the short-circuit when the static-key guard is there, and the bit-test by drm_debug_enabled_raw() otherwise. TLDR: we could change __drm_debug_enabled() to call _instrumented() instead of _raw() for the =3DN case, but that should be accompanied by some experiments and results. Signed-off-by: Jim Cromie --- -v12- restore (previously dropped) drm_debug_enabled, with __ alterations. --- drivers/gpu/drm/drm_vblank.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index f78bf37f1e0a..8ec025e12c67 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -803,15 +803,14 @@ drm_crtc_vblank_helper_get_vblank_timestamp_internal( */ *vblank_time =3D ktime_sub_ns(etime, delta_ns); =20 - if (!drm_debug_enabled(DRM_UT_VBL)) + if (!__drm_debug_enabled(DRM_UT_VBL)) return true; =20 - ts_etime =3D ktime_to_timespec64(etime); - ts_vblank_time =3D ktime_to_timespec64(*vblank_time); - drm_dbg_vbl(dev, "crtc %u : v p(%d,%d)@ %ptSp -> %ptSp [e %d us, %d rep]\n", - pipe, hpos, vpos, &ts_etime, &ts_vblank_time, + pipe, hpos, vpos, + (ts_etime =3D ktime_to_timespec64(etime), &ts_etime), + (ts_vblank_time =3D ktime_to_timespec64(*vblank_time), &ts_vblank_ti= me), duration_ns / 1000, i); =20 return true; --=20 2.53.0