On 28/04/2021 22:24, Jason Ekstrand wrote: > On Wed, Apr 28, 2021 at 3:43 AM Jani Nikula wrote: >> On Tue, 27 Apr 2021, Umesh Nerlige Ramappa wrote: >>> Perf measurements rely on CPU and engine timestamps to correlate >>> events of interest across these time domains. Current mechanisms get >>> these timestamps separately and the calculated delta between these >>> timestamps lack enough accuracy. >>> >>> To improve the accuracy of these time measurements to within a few us, >>> add a query that returns the engine and cpu timestamps captured as >>> close to each other as possible. >> Cc: dri-devel, Jason and Daniel for review. > Thanks! > >>> v2: (Tvrtko) >>> - document clock reference used >>> - return cpu timestamp always >>> - capture cpu time just before lower dword of cs timestamp >>> >>> v3: (Chris) >>> - use uncore-rpm >>> - use __query_cs_timestamp helper >>> >>> v4: (Lionel) >>> - Kernel perf subsytem allows users to specify the clock id to be used >>> in perf_event_open. This clock id is used by the perf subsystem to >>> return the appropriate cpu timestamp in perf events. Similarly, let >>> the user pass the clockid to this query so that cpu timestamp >>> corresponds to the clock id requested. >>> >>> v5: (Tvrtko) >>> - Use normal ktime accessors instead of fast versions >>> - Add more uApi documentation >>> >>> v6: (Lionel) >>> - Move switch out of spinlock >>> >>> v7: (Chris) >>> - cs_timestamp is a misnomer, use cs_cycles instead >>> - return the cs cycle frequency as well in the query >>> >>> v8: >>> - Add platform and engine specific checks >>> >>> v9: (Lionel) >>> - Return 2 cpu timestamps in the query - captured before and after the >>> register read >>> >>> v10: (Chris) >>> - Use local_clock() to measure time taken to read lower dword of >>> register and return it to user. >>> >>> v11: (Jani) >>> - IS_GEN deprecated. User GRAPHICS_VER instead. >>> >>> Signed-off-by: Umesh Nerlige Ramappa >>> --- >>> drivers/gpu/drm/i915/i915_query.c | 145 ++++++++++++++++++++++++++++++ >>> include/uapi/drm/i915_drm.h | 48 ++++++++++ >>> 2 files changed, 193 insertions(+) >>> >>> diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c >>> index fed337ad7b68..2594b93901ac 100644 >>> --- a/drivers/gpu/drm/i915/i915_query.c >>> +++ b/drivers/gpu/drm/i915/i915_query.c >>> @@ -6,6 +6,8 @@ >>> >>> #include >>> >>> +#include "gt/intel_engine_pm.h" >>> +#include "gt/intel_engine_user.h" >>> #include "i915_drv.h" >>> #include "i915_perf.h" >>> #include "i915_query.h" >>> @@ -90,6 +92,148 @@ static int query_topology_info(struct drm_i915_private *dev_priv, >>> return total_length; >>> } >>> >>> +typedef u64 (*__ktime_func_t)(void); >>> +static __ktime_func_t __clock_id_to_func(clockid_t clk_id) >>> +{ >>> + /* >>> + * Use logic same as the perf subsystem to allow user to select the >>> + * reference clock id to be used for timestamps. >>> + */ >>> + switch (clk_id) { >>> + case CLOCK_MONOTONIC: >>> + return &ktime_get_ns; >>> + case CLOCK_MONOTONIC_RAW: >>> + return &ktime_get_raw_ns; >>> + case CLOCK_REALTIME: >>> + return &ktime_get_real_ns; >>> + case CLOCK_BOOTTIME: >>> + return &ktime_get_boottime_ns; >>> + case CLOCK_TAI: >>> + return &ktime_get_clocktai_ns; >>> + default: >>> + return NULL; >>> + } >>> +} >>> + >>> +static inline int >>> +__read_timestamps(struct intel_uncore *uncore, >>> + i915_reg_t lower_reg, >>> + i915_reg_t upper_reg, >>> + u64 *cs_ts, >>> + u64 *cpu_ts, >>> + __ktime_func_t cpu_clock) >>> +{ >>> + u32 upper, lower, old_upper, loop = 0; >>> + >>> + upper = intel_uncore_read_fw(uncore, upper_reg); >>> + do { >>> + cpu_ts[1] = local_clock(); >>> + cpu_ts[0] = cpu_clock(); >>> + lower = intel_uncore_read_fw(uncore, lower_reg); >>> + cpu_ts[1] = local_clock() - cpu_ts[1]; >>> + old_upper = upper; >>> + upper = intel_uncore_read_fw(uncore, upper_reg); >>> + } while (upper != old_upper && loop++ < 2); >>> + >>> + *cs_ts = (u64)upper << 32 | lower; >>> + >>> + return 0; >>> +} >>> + >>> +static int >>> +__query_cs_cycles(struct intel_engine_cs *engine, >>> + u64 *cs_ts, u64 *cpu_ts, >>> + __ktime_func_t cpu_clock) >>> +{ >>> + struct intel_uncore *uncore = engine->uncore; >>> + enum forcewake_domains fw_domains; >>> + u32 base = engine->mmio_base; >>> + intel_wakeref_t wakeref; >>> + int ret; >>> + >>> + fw_domains = intel_uncore_forcewake_for_reg(uncore, >>> + RING_TIMESTAMP(base), >>> + FW_REG_READ); >>> + >>> + with_intel_runtime_pm(uncore->rpm, wakeref) { >>> + spin_lock_irq(&uncore->lock); >>> + intel_uncore_forcewake_get__locked(uncore, fw_domains); >>> + >>> + ret = __read_timestamps(uncore, >>> + RING_TIMESTAMP(base), >>> + RING_TIMESTAMP_UDW(base), >>> + cs_ts, >>> + cpu_ts, >>> + cpu_clock); >>> + >>> + intel_uncore_forcewake_put__locked(uncore, fw_domains); >>> + spin_unlock_irq(&uncore->lock); >>> + } >>> + >>> + return ret; >>> +} >>> + >>> +static int >>> +query_cs_cycles(struct drm_i915_private *i915, >>> + struct drm_i915_query_item *query_item) >>> +{ >>> + struct drm_i915_query_cs_cycles __user *query_ptr; >>> + struct drm_i915_query_cs_cycles query; >>> + struct intel_engine_cs *engine; >>> + __ktime_func_t cpu_clock; >>> + int ret; >>> + >>> + if (GRAPHICS_VER(i915) < 6) >>> + return -ENODEV; >>> + >>> + query_ptr = u64_to_user_ptr(query_item->data_ptr); >>> + ret = copy_query_item(&query, sizeof(query), sizeof(query), query_item); >>> + if (ret != 0) >>> + return ret; >>> + >>> + if (query.flags) >>> + return -EINVAL; >>> + >>> + if (query.rsvd) >>> + return -EINVAL; >>> + >>> + cpu_clock = __clock_id_to_func(query.clockid); >>> + if (!cpu_clock) >>> + return -EINVAL; >>> + >>> + engine = intel_engine_lookup_user(i915, >>> + query.engine.engine_class, >>> + query.engine.engine_instance); >>> + if (!engine) >>> + return -EINVAL; >>> + >>> + if (GRAPHICS_VER(i915) == 6 && >>> + query.engine.engine_class != I915_ENGINE_CLASS_RENDER) >>> + return -ENODEV; >>> + >>> + query.cs_frequency = engine->gt->clock_frequency; >>> + ret = __query_cs_cycles(engine, >>> + &query.cs_cycles, >>> + query.cpu_timestamp, >>> + cpu_clock); >>> + if (ret) >>> + return ret; >>> + >>> + if (put_user(query.cs_frequency, &query_ptr->cs_frequency)) >>> + return -EFAULT; >>> + >>> + if (put_user(query.cpu_timestamp[0], &query_ptr->cpu_timestamp[0])) >>> + return -EFAULT; >>> + >>> + if (put_user(query.cpu_timestamp[1], &query_ptr->cpu_timestamp[1])) >>> + return -EFAULT; >>> + >>> + if (put_user(query.cs_cycles, &query_ptr->cs_cycles)) >>> + return -EFAULT; >>> + >>> + return sizeof(query); >>> +} >>> + >>> static int >>> query_engine_info(struct drm_i915_private *i915, >>> struct drm_i915_query_item *query_item) >>> @@ -424,6 +568,7 @@ static int (* const i915_query_funcs[])(struct drm_i915_private *dev_priv, >>> query_topology_info, >>> query_engine_info, >>> query_perf_config, >>> + query_cs_cycles, >>> }; >>> >>> int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file) >>> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h >>> index 6a34243a7646..08b00f1709b5 100644 >>> --- a/include/uapi/drm/i915_drm.h >>> +++ b/include/uapi/drm/i915_drm.h >>> @@ -2230,6 +2230,10 @@ struct drm_i915_query_item { >>> #define DRM_I915_QUERY_TOPOLOGY_INFO 1 >>> #define DRM_I915_QUERY_ENGINE_INFO 2 >>> #define DRM_I915_QUERY_PERF_CONFIG 3 >>> + /** >>> + * Query Command Streamer timestamp register. >>> + */ >>> +#define DRM_I915_QUERY_CS_CYCLES 4 >>> /* Must be kept compact -- no holes and well documented */ >>> >>> /** >>> @@ -2397,6 +2401,50 @@ struct drm_i915_engine_info { >>> __u64 rsvd1[4]; >>> }; >>> >>> +/** >>> + * struct drm_i915_query_cs_cycles >>> + * >>> + * The query returns the command streamer cycles and the frequency that can be >>> + * used to calculate the command streamer timestamp. In addition the query >>> + * returns a set of cpu timestamps that indicate when the command streamer cycle >>> + * count was captured. >>> + */ >>> +struct drm_i915_query_cs_cycles { >>> + /** Engine for which command streamer cycles is queried. */ >>> + struct i915_engine_class_instance engine; > Why is this per-engine? Do we actually expect it to change between > engines? Each engine has its own timestamp register. > If so, we may have a problem because Vulkan expects a > unified timestamp domain for all command streamer timestamp queries. I don't think it does : " Timestamps*may*only be meaningfully compared if they are written by commands submitted to the same queue. " [1] [1] : https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkCmdWriteTimestamp.html -Lionel > > --Jason > > >>> + /** Must be zero. */ >>> + __u32 flags; >>> + >>> + /** >>> + * Command streamer cycles as read from the command streamer >>> + * register at 0x358 offset. >>> + */ >>> + __u64 cs_cycles; >>> + >>> + /** Frequency of the cs cycles in Hz. */ >>> + __u64 cs_frequency; >>> + >>> + /** >>> + * CPU timestamps in ns. cpu_timestamp[0] is captured before reading the >>> + * cs_cycles register using the reference clockid set by the user. >>> + * cpu_timestamp[1] is the time taken in ns to read the lower dword of >>> + * the cs_cycles register. >>> + */ >>> + __u64 cpu_timestamp[2]; >>> + >>> + /** >>> + * Reference clock id for CPU timestamp. For definition, see >>> + * clock_gettime(2) and perf_event_open(2). Supported clock ids are >>> + * CLOCK_MONOTONIC, CLOCK_MONOTONIC_RAW, CLOCK_REALTIME, CLOCK_BOOTTIME, >>> + * CLOCK_TAI. >>> + */ >>> + __s32 clockid; >>> + >>> + /** Must be zero. */ >>> + __u32 rsvd; >>> +}; >>> + >>> /** >>> * struct drm_i915_query_engine_info >>> * >> -- >> Jani Nikula, Intel Open Source Graphics Center