diff --git a/docs/sources/mono-api-gc.html b/docs/sources/mono-api-gc.html index 20d6cb9dc9b3..cddef0364cbf 100644 --- a/docs/sources/mono-api-gc.html +++ b/docs/sources/mono-api-gc.html @@ -40,9 +40,8 @@

SGen Bridge

The output of the SCC analysis is passed to the `cross_references()` callback. It is expected to set the `is_alive` flag on those strongly connected components that it - wishes to be kept alive. Only bridged objects will be - reported to the callback, i.e., non-bridged objects are - removed from the callback graph. + wishes to be kept alive. The value of `is_alive` will be + ignored on any SCCs which lack bridges.

In monodroid each bridged object has a corresponding Java mirror object. In the bridge callback it reifies the Mono @@ -63,7 +62,7 @@

SGen Bridge

enum { - SGEN_BRIDGE_VERSION = 4 + SGEN_BRIDGE_VERSION = 5 }; typedef enum { diff --git a/mono/metadata/sgen-bridge.h b/mono/metadata/sgen-bridge.h index b11df8a17b5e..a03b0a81bfd5 100644 --- a/mono/metadata/sgen-bridge.h +++ b/mono/metadata/sgen-bridge.h @@ -17,8 +17,8 @@ * When SGen is done marking, it puts together a list of all dead bridged * objects. This is passed to the bridge processor, which does an analysis to * simplify the graph: It replaces strongly-connected components with single - * nodes, and then removes any nodes corresponding to components which do not - * contain bridged objects. + * nodes, and may remove nodes corresponding to components which do not contain + * bridged objects. * * The output of the SCC analysis is passed to the client's `cross_references()` * callback. This consists of 2 arrays, an array of SCCs (MonoGCBridgeSCC), @@ -54,7 +54,7 @@ MONO_BEGIN_DECLS enum { - SGEN_BRIDGE_VERSION = 4 + SGEN_BRIDGE_VERSION = 5 }; typedef enum { diff --git a/mono/metadata/sgen-tarjan-bridge.c b/mono/metadata/sgen-tarjan-bridge.c index c4087a6076e3..69230336141a 100644 --- a/mono/metadata/sgen-tarjan-bridge.c +++ b/mono/metadata/sgen-tarjan-bridge.c @@ -122,7 +122,15 @@ typedef struct _ScanData { unsigned obj_state : 2; } ScanData; +// Should color be made visible to client even though it has no bridges? +static inline gboolean bridgeless_color_is_heavy (ColorData *data) { + return TRUE; +} +// Should color be made visible to client? +static inline gboolean color_visible_to_client (ColorData *data) { + return dyn_array_ptr_size (&data->bridges) || bridgeless_color_is_heavy (data); +} // Stacks of ScanData objects used for tarjan algorithm. // The Tarjan algorithm is normally defined recursively; here scan_stack simulates the call stack of a recursive algorithm, @@ -159,6 +167,7 @@ static ObjectBucket *root_object_bucket; static ObjectBucket *cur_object_bucket; static int object_data_count; +// Arenas to allocate ScanData from static ObjectBucket* new_object_bucket (void) { @@ -211,7 +220,7 @@ free_object_buckets (void) //ColorData buckets #define NUM_COLOR_ENTRIES ((BUCKET_SIZE - SIZEOF_VOID_P * 2) / sizeof (ColorData)) -// Same as ObjectBucket except NUM_COLOR_ENTRIES and NUM_SCAN_ENTRIES differ +// Arenas for ColorDatas, same as ObjectBucket except items-per-bucket differs typedef struct _ColorBucket ColorBucket; struct _ColorBucket { ColorBucket *next; @@ -358,7 +367,9 @@ typedef struct { } HashEntry; /* -We tried 2/32, 2/128, 4/32, 4/128, 6/128 and 8/128. +The merge cache maps an ordered list of ColorDatas [the color_merge_array] to a single ColorData. + +About cache bucket tuning: We tried 2/32, 2/128, 4/32, 4/128, 6/128 and 8/128. The performance cost between 4/128 and 8/128 is so small since cache movement happens completely in the same cacheline, making the extra space pretty much free. @@ -409,8 +420,9 @@ match_colors (DynPtrArray *a, DynPtrArray *b) return TRUE; } -static int cache_hits, cache_misses; +static int cache_hits, cache_misses, cache_abstains; +// The cache contains only non-bridged colors. static ColorData* find_in_cache (int *insert_index) { @@ -419,8 +431,10 @@ find_in_cache (int *insert_index) size = dyn_array_ptr_size (&color_merge_array); /* Cache checking is very ineficient with a lot of elements*/ - if (size > 3) + if (size > 3) { + ++cache_abstains; return NULL; + } hash = 0; for (i = 0 ; i < size; ++i) @@ -448,13 +462,15 @@ find_in_cache (int *insert_index) return NULL; } +// A color is needed for an SCC. If the SCC has bridges, the color MUST be newly allocated. +// If the SCC lacks bridges, the allocator MAY use the cache to merge it with an existing one. static ColorData* -new_color (gboolean force_new) +new_color (gboolean has_bridges) { int i = -1; ColorData *cd; /* XXX Try to find an equal one and return it */ - if (!force_new) { + if (!has_bridges) { cd = find_in_cache (&i); if (cd) return cd; @@ -606,16 +622,24 @@ compute_low (ScanData *data) #include "sgen/sgen-scan-object.h" } +// A non-bridged object needs a single color describing the current merge array. static ColorData* reduce_color (void) { ColorData *color = NULL; int size = dyn_array_ptr_size (&color_merge_array); + // Merge array is empty-- this SCC points to no bridged colors. + // This SCC can be ignored completely. if (size == 0) color = NULL; + + // Merge array has one item-- this SCC points to a single bridged color. + // This SCC can be forwarded to the pointed-to color. else if (size == 1) { color = (ColorData *)dyn_array_ptr_get (&color_merge_array, 0); + + // This SCC gets to talk to the color allocator. } else color = new_color (FALSE); @@ -889,7 +913,7 @@ gather_xrefs (ColorData *color) if (src->visited) continue; src->visited = TRUE; - if (dyn_array_ptr_size (&src->bridges)) + if (color_visible_to_client (src)) dyn_array_ptr_add (&color_merge_array, src); else gather_xrefs (src); @@ -905,7 +929,7 @@ reset_xrefs (ColorData *color) if (!src->visited) continue; src->visited = FALSE; - if (!dyn_array_ptr_size (&src->bridges)) + if (!color_visible_to_client (src)) reset_xrefs (src); } } @@ -934,15 +958,26 @@ processing_build_callback_data (int generation) printf ("number of SCCs %d\n", num_colors_with_bridges); #endif + // Count the number of SCCs visible to the client + int num_sccs = 0; + for (cur = root_color_bucket; cur; cur = cur->next) { + ColorData *cd; + for (cd = &cur->data [0]; cd < cur->next_data; ++cd) { + if (color_visible_to_client (cd)) + num_sccs++; + } + } + /* This is a straightforward translation from colors to the bridge callback format. */ - api_sccs = (MonoGCBridgeSCC **)sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC*) * num_colors_with_bridges, INTERNAL_MEM_BRIDGE_DATA, TRUE); + api_sccs = (MonoGCBridgeSCC **)sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC*) * num_sccs, INTERNAL_MEM_BRIDGE_DATA, TRUE); api_index = xref_count = 0; + // Convert visible SCCs, along with their bridged object list, to MonoGCBridgeSCCs in the client's SCC list for (cur = root_color_bucket; cur; cur = cur->next) { ColorData *cd; for (cd = &cur->data [0]; cd < cur->next_data; ++cd) { int bridges = dyn_array_ptr_size (&cd->bridges); - if (!bridges) + if (!(bridges || bridgeless_color_is_heavy (cd))) continue; api_sccs [api_index] = (MonoGCBridgeSCC *)sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC) + sizeof (MonoObject*) * bridges, INTERNAL_MEM_BRIDGE_DATA, TRUE); @@ -959,11 +994,11 @@ processing_build_callback_data (int generation) scc_setup_time = step_timer (&curtime); + // Eliminate non-visible SCCs from the SCC list and redistribute xrefs for (cur = root_color_bucket; cur; cur = cur->next) { ColorData *cd; for (cd = &cur->data [0]; cd < cur->next_data; ++cd) { - int bridges = dyn_array_ptr_size (&cd->bridges); - if (!bridges) + if (!color_visible_to_client (cd)) continue; dyn_array_ptr_empty (&color_merge_array); @@ -981,18 +1016,18 @@ processing_build_callback_data (int generation) dump_color_table (" after xref pass", TRUE); #endif + // Write out xrefs array api_xrefs = (MonoGCBridgeXRef *)sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeXRef) * xref_count, INTERNAL_MEM_BRIDGE_DATA, TRUE); api_index = 0; for (cur = root_color_bucket; cur; cur = cur->next) { ColorData *src; for (src = &cur->data [0]; src < cur->next_data; ++src) { - int bridges = dyn_array_ptr_size (&src->bridges); - if (!bridges) + if (!color_visible_to_client (src)) continue; for (j = 0; j < dyn_array_ptr_size (&src->other_colors); ++j) { ColorData *dest = (ColorData *)dyn_array_ptr_get (&src->other_colors, j); - g_assert (dyn_array_ptr_size (&dest->bridges)); /* We flattened the color graph, so this must never happen. */ + g_assert (color_visible_to_client (dest)); /* Supposedly we already eliminated all xrefs to non-visible objects. */ api_xrefs [api_index].src_scc_index = src->api_index; api_xrefs [api_index].dst_scc_index = dest->api_index; @@ -1011,7 +1046,7 @@ processing_build_callback_data (int generation) #endif //FIXME move half of the cleanup to before the bridge callback? - bridge_processor->num_sccs = num_colors_with_bridges; + bridge_processor->num_sccs = num_sccs; bridge_processor->api_sccs = api_sccs; bridge_processor->num_xrefs = xref_count; bridge_processor->api_xrefs = api_xrefs; @@ -1033,10 +1068,10 @@ processing_after_callback (int generation) cleanup_time = step_timer (&curtime); - mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC, "GC_TAR_BRIDGE bridges %d objects %d colors %d ignored %d sccs %d xref %d cache %d/%d setup %.2fms tarjan %.2fms scc-setup %.2fms gather-xref %.2fms xref-setup %.2fms cleanup %.2fms", + mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC, "GC_TAR_BRIDGE bridges %d objects %d colors %d ignored %d sccs %d xref %d cache %d/%d/%d setup %.2fms tarjan %.2fms scc-setup %.2fms gather-xref %.2fms xref-setup %.2fms cleanup %.2fms", bridge_count, object_count, color_count, ignored_objects, scc_count, xref_count, - cache_hits, cache_misses, + cache_hits, cache_misses, cache_abstains, setup_time / 10000.0f, tarjan_time / 10000.0f, scc_setup_time / 10000.0f, @@ -1044,7 +1079,7 @@ processing_after_callback (int generation) xref_setup_time / 10000.0f, cleanup_time / 10000.0f); - cache_hits = cache_misses = 0; + cache_hits = cache_misses = cache_abstains = 0; ignored_objects = 0; }