[PATCH v4 1/2] lib: Add DRM driver sysfs profiling knob toggling functions
Adrián Larumbe
adrian.larumbe at collabora.com
Thu May 23 11:45:43 UTC 2024
Some DRM drivers need to have their accounting HW toggled on demand from
user space so that fdinfo's drm-engine and drm-cycles tags can be updated
upon job completion.
A profiler such as gputop should be able to check which DRM devices have
such a sysfs knob, record its original state, toggle-enable it and revert
this operation right before exiting.
Also create a new static library dependency for this family of functions so
that it can later be linked against gputop.
Cc: Tvrtko Ursulin <tursulin at ursulin.net>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
Cc: Kamil Konieczny <kamil.konieczny at linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe at collabora.com>
---
lib/igt_profiling.c | 190 ++++++++++++++++++++++++++++++++++++++++++++
lib/igt_profiling.h | 22 +++++
lib/meson.build | 8 ++
3 files changed, 220 insertions(+)
create mode 100644 lib/igt_profiling.c
create mode 100644 lib/igt_profiling.h
diff --git a/lib/igt_profiling.c b/lib/igt_profiling.c
new file mode 100644
index 000000000000..0a21c1fa0672
--- /dev/null
+++ b/lib/igt_profiling.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Collabora Ltd.
+ *
+ * Author: Adrian Larumbe <adrian.larumbe at collabora.com>
+ *
+ */
+
+#include <unistd.h>
+#include <assert.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "igt_profiling.h"
+
+#define SYSFS_DRM "/sys/class/drm"
+#define NUM_DEVICES 10
+
+/**
+ * igt_devices_profiled
+ *
+ * Gives us an array of igt_profiled_device structures, each of which contains
+ * the full path of the DRM device's sysfs profiling knob and its original
+ * state, so that it can be restored later on.
+ *
+ * Returns: NULL-terminated array of struct igt_profiled_device pointers, or
+ * NULL on failure.
+ */
+struct igt_profiled_device *igt_devices_profiled(void)
+{
+ struct igt_profiled_device *profiled_devices;
+ unsigned int devlist_len = NUM_DEVICES;
+ unsigned int i = 0;
+ struct dirent *entry;
+ DIR *dev_dir;
+
+ /* The return array will be resized in case there are too many devices */
+ profiled_devices = malloc(devlist_len * sizeof(struct igt_profiled_device));
+ if (!profiled_devices)
+ return NULL;
+
+ dev_dir = opendir(SYSFS_DRM);
+ if (!dev_dir)
+ goto end;
+
+ while ((entry = readdir(dev_dir)) != NULL) {
+ char path[PATH_MAX];
+ char orig_state;
+ int sysfs_fd;
+
+ /* All DRM device entries are symlinks to other paths within sysfs */
+ if (entry->d_type != DT_LNK)
+ continue;
+
+ /* We're only interested in render nodes */
+ if (strstr(entry->d_name, "render") != entry->d_name)
+ continue;
+
+ snprintf(path, sizeof(path), "%s/%s/device/%s",
+ SYSFS_DRM, entry->d_name, "profiling");
+
+ if (access(path, F_OK))
+ continue;
+
+ sysfs_fd = open(path, O_RDONLY);
+ if (sysfs_fd == -1)
+ continue;
+
+ if (read(sysfs_fd, &orig_state, 1) <= 0) {
+ close(sysfs_fd);
+ continue;
+ }
+
+ if (i == (devlist_len - 1)) {
+ struct igt_profiled_device *new_profiled_devices;
+
+ devlist_len += NUM_DEVICES;
+ new_profiled_devices = realloc(profiled_devices, devlist_len);
+ if (!new_profiled_devices)
+ goto end;
+ profiled_devices = new_profiled_devices;
+ }
+
+ profiled_devices[i].syspath = strdup(path);
+ profiled_devices[i++].original_state = orig_state;
+
+ close(sysfs_fd);
+ }
+
+ if (i == 0)
+ goto end;
+ else
+ profiled_devices[i].syspath = NULL; /* Array terminator */
+
+ return profiled_devices;
+
+end:
+ free(profiled_devices);
+ return NULL;
+}
+
+/**
+ * igt_devices_configure_profiling
+ * @devices: NULL-terminated array of igt_profiled_device structures.
+ * @enable: If True, then enable profiling, otherwise restore to original state
+ *
+ * For every single device's profiling knob sysfs path in the NULL-terminated
+ * 'devices' array, set it to '1' if bool equals true. Otherwise set it to
+ * its original state at the time it was first probed in igt_devices_profiled
+ *
+ */
+void igt_devices_configure_profiling(struct igt_profiled_device *devices, bool enable)
+{
+ assert(devices);
+
+ for (unsigned int i = 0; devices[i].syspath; i++) {
+
+ int sysfs_fd = open(devices[i].syspath, O_WRONLY);
+
+ if (sysfs_fd < 0)
+ continue;
+
+ write(sysfs_fd, enable ? "1" : &devices[i].original_state, 1);
+ close(sysfs_fd);
+ }
+}
+
+/**
+ * igt_devices_configure_profiling
+ * @devices: NULL-terminated array of igt_profiled_device structures.
+ *
+ * For every single struct igt_profiled_device in the 'devices' array,
+ * free its duplicated syspath string, and then free the array itself.
+ *
+ */
+void igt_devices_free_profiling(struct igt_profiled_device *devices)
+{
+ assert(devices);
+
+ for (unsigned int i = 0; devices[i].syspath; i++)
+ free(devices[i].syspath);
+
+ free(devices);
+}
+
+/**
+ * igt_devices_configure_profiling
+ * @devices: NULL-terminated array of igt_profiled_device structures.
+ *
+ * For every single struct igt_profiled_device in the 'devices' array,
+ * check whether the sysfs profiling knob has changed its state since
+ * the last time its original state was registered, and then update it
+ * accordingly. This is usually a symptom that there are other profilers
+ * currently trying to toggle the sysfs knob, or perhaps more than one
+ * instance of the same profiler.
+ * The goal of this function is ensuring the sysfs knob is eventually
+ * restored to a coherent state, even though a small race window is
+ * possible. There's nothing we can do about this, so this function
+ * tries to mitigate that situation in a best-effort fashion.
+ *
+ */
+void igt_devices_update_original_profiling_state(struct igt_profiled_device *devices)
+{
+ assert(devices);
+
+ for (unsigned int i = 0; devices[i].syspath; i++) {
+ char new_state;
+ int sysfs_fd;
+
+ sysfs_fd = open(devices[i].syspath, O_RDWR);
+ if (sysfs_fd == -1)
+ continue;
+
+ if (!read(sysfs_fd, &new_state, 1)) {
+ close(sysfs_fd);
+ continue;
+ }
+
+ if (new_state == '0') {
+ write(sysfs_fd, "1", 1);
+ devices[i].original_state = new_state;
+ }
+
+ close(sysfs_fd);
+ }
+}
diff --git a/lib/igt_profiling.h b/lib/igt_profiling.h
new file mode 100644
index 000000000000..b711d2cd2d19
--- /dev/null
+++ b/lib/igt_profiling.h
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Collabora Ltd.
+ *
+ * Author: Adrian Larumbe <adrian.larumbe at collabora.com>
+ *
+ */
+
+#ifndef IGT_PROFILING_H
+#define IGT_PROFILING_H
+
+struct igt_profiled_device {
+ char *syspath;
+ char original_state;
+};
+
+void igt_devices_configure_profiling(struct igt_profiled_device *devices, bool enable);
+struct igt_profiled_device *igt_devices_profiled(void);
+void igt_devices_free_profiling(struct igt_profiled_device *devices);
+void igt_devices_update_original_profiling_state(struct igt_profiled_device *devices);
+
+#endif /* IGT_PROFILING_H */
diff --git a/lib/meson.build b/lib/meson.build
index e2f740c116f8..6f61ed5c558b 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -291,6 +291,14 @@ lib_igt_drm_fdinfo_build = static_library('igt_drm_fdinfo',
lib_igt_drm_fdinfo = declare_dependency(link_with : lib_igt_drm_fdinfo_build,
include_directories : inc)
+
+lib_igt_profiling_build = static_library('igt_profiling',
+ ['igt_profiling.c'],
+ include_directories : inc)
+
+lib_igt_profiling = declare_dependency(link_with : lib_igt_profiling_build,
+ include_directories : inc)
+
i915_perf_files = [
'igt_list.c',
'i915/perf.c',
--
2.45.1
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