[Mesa-dev] [PATCH 1/2] st/mesa: regularly re-pin driver threads to the CCX where the app thread is

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

This is used when glthread is disabled.

Mesa pretty much chases the app thread on the CPU.
The performance is the same as pinning the app thread.
---
 src/mesa/state_tracker/st_context.h |  2 ++
 src/mesa/state_tracker/st_draw.c    | 32 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/mesa/state_tracker/st_context.h b/src/mesa/state_tracker/st_context.h
index 14b9b018809..95133c7020f 100644
--- a/src/mesa/state_tracker/st_context.h
+++ b/src/mesa/state_tracker/st_context.h
@@ -186,20 +186,22 @@ struct st_context
       uint8_t sample_locations[
          PIPE_MAX_SAMPLE_LOCATION_GRID_SIZE *
          PIPE_MAX_SAMPLE_LOCATION_GRID_SIZE * 32];
    } state;
 
    uint64_t dirty; /**< dirty states */
 
    /** This masks out unused shader resources. Only valid in draw calls. */
    uint64_t active_states;
 
+   unsigned pin_thread_counter; /* for L3 thread pinning on AMD Zen */
+
    /* If true, further analysis of states is required to know if something
     * has changed. Used mainly for shaders.
     */
    bool gfx_shaders_may_be_dirty;
    bool compute_shader_may_be_dirty;
 
    GLboolean vertdata_edgeflags;
    GLboolean edgeflag_culls_prims;
 
    struct st_vertex_program *vp;    /**< Currently bound vertex program */
diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
index eb52d9505b6..5910ffa5bda 100644
--- a/src/mesa/state_tracker/st_draw.c
+++ b/src/mesa/state_tracker/st_draw.c
@@ -51,28 +51,36 @@
 #include "st_atom.h"
 #include "st_cb_bitmap.h"
 #include "st_cb_bufferobjects.h"
 #include "st_cb_xformfb.h"
 #include "st_debug.h"
 #include "st_draw.h"
 #include "st_program.h"
 
 #include "pipe/p_context.h"
 #include "pipe/p_defines.h"
+#include "util/u_cpu_detect.h"
 #include "util/u_inlines.h"
 #include "util/u_format.h"
 #include "util/u_prim.h"
 #include "util/u_draw.h"
 #include "util/u_upload_mgr.h"
 #include "draw/draw_context.h"
 #include "cso_cache/cso_context.h"
 
+#ifdef PIPE_OS_LINUX
+#include <sched.h>
+#define HAVE_SCHED_GETCPU 1
+#else
+#define sched_getcpu() 0
+#define HAVE_SCHED_GETCPU 0
+#endif
 
 /**
  * Set the restart index.
  */
 static void
 setup_primitive_restart(struct gl_context *ctx, struct pipe_draw_info *info)
 {
    if (ctx->Array._PrimitiveRestart) {
       unsigned index_size = info->index_size;
 
@@ -115,20 +123,44 @@ prepare_draw(struct st_context *st, struct gl_context *ctx)
    if (unlikely(!st->bitmap.cache.empty))
       st_flush_bitmap_cache(st);
 
    st_invalidate_readpix_cache(st);
 
    /* Validate state. */
    if ((st->dirty | ctx->NewDriverState) & ST_PIPELINE_RENDER_STATE_MASK ||
        st->gfx_shaders_may_be_dirty) {
       st_validate_state(st, ST_PIPELINE_RENDER);
    }
+
+   struct pipe_context *pipe = st->pipe;
+
+   /* Pin threads regularly to the same Zen CCX that the main thread is
+    * running on. The main thread can move between CCXs.
+    */
+   if (unlikely(HAVE_SCHED_GETCPU && /* Linux */
+                /* AMD Zen */
+                util_cpu_caps.nr_cpus != util_cpu_caps.cores_per_L3 &&
+                /* no glthread */
+                ctx->CurrentClientDispatch != ctx->MarshalExec &&
+                /* driver support */
+                pipe->set_context_param &&
+                /* do it occasionally */
+                ++st->pin_thread_counter % 512 == 0)) {
+      int cpu = sched_getcpu();
+      if (cpu >= 0) {
+         unsigned L3_cache = cpu / util_cpu_caps.cores_per_L3;
+
+         pipe->set_context_param(pipe,
+                                 PIPE_CONTEXT_PARAM_PIN_THREADS_TO_L3_CACHE,
+                                 L3_cache);
+      }
+   }
 }
 
 /**
  * This function gets plugged into the VBO module and is called when
  * we have something to render.
  * Basically, translate the information into the format expected by gallium.
  */
 static void
 st_draw_vbo(struct gl_context *ctx,
             const struct _mesa_prim *prims,
-- 
2.17.1