From d5db150801023c307fcbe1cd98b4fd8e2d27b55e Mon Sep 17 00:00:00 2001 From: Vito Caputo Date: Fri, 10 Jun 2022 20:11:23 -0700 Subject: til: introduce til_frame_plan_t and .cpu_affinity modules/checkers w/fill_module=$module requires a consistent mapping of cpu to fragnum since it creates a per-cpu til_module_context_t for the fill_module. The existing implementation for threaded rendering maximizes performance by letting *any* scheduled to run thread advance fragnum atomically and render the acquired fragnum indiscriminately. A side effect of this is any given frame, even rendered by the same module, will have a random mapping of cpus/threads to fragnums. With this change, the simple til_module_t.prepare_frame() API of returning a bare fragmenter function is changed to instead return a "frame plan" in til_frame_plan_t. Right now til_frame_plan_t just contains the same fragmenter as before, but also has a .cpu_affinity member for setting if the frame requires a stable relationship of cpu/thread to fragnum. Setting .cpu_affinity should be avoided if unnecessary, and that is the default if you don't mention .cpu_affinity at all when initializing the plan in the ergonomic manner w/designated initializers. This is because the way .cpu_affinity is implemented will leave threads spinning while they poll for *their* next fragnum using atomic intrinsics. There's probably some room for improvement here, but this is good enough for now to get things working and correct. --- src/til.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'src/til.h') diff --git a/src/til.h b/src/til.h index ab8f6b8..e38ad9c 100644 --- a/src/til.h +++ b/src/til.h @@ -5,10 +5,16 @@ #include "til_module_context.h" #include "til_setup.h" -/* til_fragmenter produces fragments from an input fragment, num being the desired fragment for the current call. +/* til_fragmenter_t produces fragments from an input fragment, num being the desired fragment for the current call. * return value of 1 means a fragment has been produced, 0 means num is beyond the end of fragments. */ typedef int (*til_fragmenter_t)(til_module_context_t *context, const til_fb_fragment_t *fragment, unsigned number, til_fb_fragment_t *res_fragment); +/* til_frame_plan_t is what til_module_t.prepare_frame() populates to return a fragmenter and any flags/rules */ +typedef struct til_frame_plan_t { + unsigned cpu_affinity:1; /* maintain a stable fragnum:cpu/thread mapping? (slower) */ + til_fragmenter_t fragmenter; /* fragmenter to use in rendering the frame */ +} til_frame_plan_t; + typedef struct til_settings_t settings; typedef struct til_setting_desc_t til_setting_desc_t; typedef struct til_knob_t til_knob_t; @@ -18,7 +24,7 @@ typedef struct til_knob_t til_knob_t; typedef struct til_module_t { til_module_context_t * (*create_context)(unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup); void (*destroy_context)(til_module_context_t *context); - void (*prepare_frame)(til_module_context_t *context, unsigned ticks, til_fb_fragment_t *fragment, til_fragmenter_t *res_fragmenter); + void (*prepare_frame)(til_module_context_t *context, unsigned ticks, til_fb_fragment_t *fragment, til_frame_plan_t *res_frame_plan); void (*render_fragment)(til_module_context_t *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment); void (*finish_frame)(til_module_context_t *context, unsigned ticks, til_fb_fragment_t *fragment); int (*setup)(const til_settings_t *settings, til_setting_t **res_setting, const til_setting_desc_t **res_desc, til_setup_t **res_setup); -- cgit v1.2.1