st/mesa: regularly re-pin driver threads to the CCX where the app thread is

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.

Reviewed-by: Dave Airlie <[email protected]>

2 files changed, 34 insertions, 0 deletions

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
@@ -193,6 +193,8 @@ struct st_context
    /** 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.
     */
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
@@ -58,6 +58,7 @@
 
 #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"
@@ -66,6 +67,13 @@
 #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.
@@ -122,6 +130,30 @@ prepare_draw(struct st_context *st, struct gl_context *ctx)
        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);
+      }
+   }
 }
 
 /**