Merge pull request #5002 from BrzVlad/feature-sgen-modes
[mono.git] / mono / sgen / sgen-gc.c
index fb6082ab6ab097da6911bab9a45fa1e0280ecead..6cd939553a99cb91d0553e6a2e80e035fccbae43 100644 (file)
 #include "mono/utils/hazard-pointer.h"
 
 #include <mono/utils/memcheck.h>
+#include <mono/utils/mono-mmap-internals.h>
 
 #undef pthread_create
 #undef pthread_join
@@ -235,6 +236,9 @@ static gboolean do_dump_nursery_content = FALSE;
 static gboolean enable_nursery_canaries = FALSE;
 
 static gboolean precleaning_enabled = TRUE;
+static gboolean dynamic_nursery = FALSE;
+static size_t min_nursery_size = 0;
+static size_t max_nursery_size = 0;
 
 #ifdef HEAVY_STATISTICS
 guint64 stat_objects_alloced_degraded = 0;
@@ -267,6 +271,8 @@ static guint64 stat_pinned_objects = 0;
 static guint64 time_minor_pre_collection_fragment_clear = 0;
 static guint64 time_minor_pinning = 0;
 static guint64 time_minor_scan_remsets = 0;
+static guint64 time_minor_scan_major_blocks = 0;
+static guint64 time_minor_scan_los = 0;
 static guint64 time_minor_scan_pinned = 0;
 static guint64 time_minor_scan_roots = 0;
 static guint64 time_minor_finish_gray_stack = 0;
@@ -285,6 +291,9 @@ static guint64 time_major_fragment_creation = 0;
 
 static guint64 time_max = 0;
 
+static int sgen_max_pause_time = SGEN_DEFAULT_MAX_PAUSE_TIME;
+static float sgen_max_pause_margin = SGEN_DEFAULT_MAX_PAUSE_MARGIN;
+
 static SGEN_TV_DECLARE (time_major_conc_collection_start);
 static SGEN_TV_DECLARE (time_major_conc_collection_end);
 
@@ -327,13 +336,32 @@ nursery_canaries_enabled (void)
 
 #if defined(HAVE_CONC_GC_AS_DEFAULT)
 /* Use concurrent major on deskstop platforms */
-#define DEFAULT_MAJOR_INIT sgen_marksweep_conc_init
-#define DEFAULT_MAJOR_NAME "marksweep-conc"
+#define DEFAULT_MAJOR SGEN_MAJOR_CONCURRENT
 #else
-#define DEFAULT_MAJOR_INIT sgen_marksweep_init
-#define DEFAULT_MAJOR_NAME "marksweep"
+#define DEFAULT_MAJOR SGEN_MAJOR_SERIAL
 #endif
 
+typedef enum {
+       SGEN_MAJOR_DEFAULT,
+       SGEN_MAJOR_SERIAL,
+       SGEN_MAJOR_CONCURRENT,
+       SGEN_MAJOR_CONCURRENT_PARALLEL
+} SgenMajor;
+
+typedef enum {
+       SGEN_MINOR_DEFAULT,
+       SGEN_MINOR_SIMPLE,
+       SGEN_MINOR_SIMPLE_PARALLEL,
+       SGEN_MINOR_SPLIT
+} SgenMinor;
+
+typedef enum {
+       SGEN_MODE_NONE,
+       SGEN_MODE_BALANCED,
+       SGEN_MODE_THROUGHPUT,
+       SGEN_MODE_PAUSE
+} SgenMode;
+
 /*
  * ######################################################################
  * ########  Global data.
@@ -354,7 +382,7 @@ static volatile mword highest_heap_address = 0;
 MonoCoopMutex sgen_interruption_mutex;
 
 int current_collection_generation = -1;
-static volatile gboolean concurrent_collection_in_progress = FALSE;
+volatile gboolean concurrent_collection_in_progress = FALSE;
 
 /* objects that are ready to be finalized */
 static SgenPointerQueue fin_ready_queue = SGEN_POINTER_QUEUE_INIT (INTERNAL_MEM_FINALIZE_READY);
@@ -426,8 +454,6 @@ sgen_workers_get_job_gray_queue (WorkerData *worker_data, SgenGrayQueue *default
 static void
 gray_queue_redirect (SgenGrayQueue *queue)
 {
-       SGEN_ASSERT (0, concurrent_collection_in_progress, "Where are we redirecting the gray queue to, without a concurrent collection?");
-
        sgen_workers_take_from_queue (queue);
 }
 
@@ -529,7 +555,7 @@ pin_objects_from_nursery_pin_queue (gboolean do_scan_objects, ScanCopyContext ct
        void **start =  sgen_pinning_get_entry (section->pin_queue_first_entry);
        void **end = sgen_pinning_get_entry (section->pin_queue_last_entry);
        void *start_nursery = section->data;
-       void *end_nursery = section->next_data;
+       void *end_nursery = section->end_data;
        void *last = NULL;
        int count = 0;
        void *search_start;
@@ -945,41 +971,51 @@ sgen_update_heap_boundaries (mword low, mword high)
  * in the nursery. The nursery is stored in nursery_section.
  */
 static void
-alloc_nursery (void)
+alloc_nursery (gboolean dynamic, size_t min_size, size_t max_size)
 {
-       GCMemSection *section;
        char *data;
        size_t scan_starts;
-       size_t alloc_size;
 
-       if (nursery_section)
-               return;
-       SGEN_LOG (2, "Allocating nursery size: %zu", (size_t)sgen_nursery_size);
-       /* later we will alloc a larger area for the nursery but only activate
-        * what we need. The rest will be used as expansion if we have too many pinned
-        * objects in the existing nursery.
-        */
-       /* FIXME: handle OOM */
-       section = (GCMemSection *)sgen_alloc_internal (INTERNAL_MEM_SECTION);
+       if (dynamic) {
+               if (!min_size)
+                       min_size = SGEN_DEFAULT_NURSERY_MIN_SIZE;
+               if (!max_size)
+                       max_size = SGEN_DEFAULT_NURSERY_MAX_SIZE;
+       } else {
+               SGEN_ASSERT (0, min_size == max_size, "We can't have nursery ranges for static configuration.");
+               if (!min_size)
+                       min_size = max_size = SGEN_DEFAULT_NURSERY_SIZE;
+       }
 
-       alloc_size = sgen_nursery_size;
+       SGEN_ASSERT (0, !nursery_section, "Why are we allocating the nursery twice?");
+       SGEN_LOG (2, "Allocating nursery size: %zu, initial %zu", max_size, min_size);
 
-       /* If there isn't enough space even for the nursery we should simply abort. */
-       g_assert (sgen_memgov_try_alloc_space (alloc_size, SPACE_NURSERY));
+       /* FIXME: handle OOM */
+       nursery_section = (GCMemSection *)sgen_alloc_internal (INTERNAL_MEM_SECTION);
 
-       data = (char *)major_collector.alloc_heap (alloc_size, alloc_size, DEFAULT_NURSERY_BITS);
-       sgen_update_heap_boundaries ((mword)data, (mword)(data + sgen_nursery_size));
-       SGEN_LOG (4, "Expanding nursery size (%p-%p): %lu, total: %lu", data, data + alloc_size, (unsigned long)sgen_nursery_size, (unsigned long)sgen_gc_get_total_heap_allocation ());
-       section->data = section->next_data = data;
-       section->size = alloc_size;
-       section->end_data = data + sgen_nursery_size;
-       scan_starts = (alloc_size + SCAN_START_SIZE - 1) / SCAN_START_SIZE;
-       section->scan_starts = (char **)sgen_alloc_internal_dynamic (sizeof (char*) * scan_starts, INTERNAL_MEM_SCAN_STARTS, TRUE);
-       section->num_scan_start = scan_starts;
+       /* If there isn't enough space even for the nursery we should simply abort. */
+       g_assert (sgen_memgov_try_alloc_space (max_size, SPACE_NURSERY));
 
-       nursery_section = section;
+       /*
+        * The nursery section range represents the memory section where objects
+        * can be found. This is used when iterating for objects in the nursery,
+        * pinning etc. sgen_nursery_max_size represents the total allocated space
+        * for the nursery. sgen_nursery_size represents the current size of the
+        * nursery and it is used for allocation limits, heuristics etc. The
+        * nursery section is not always identical to the current nursery size
+        * because it can contain pinned objects from when the nursery was larger.
+        *
+        * sgen_nursery_size <= nursery_section size <= sgen_nursery_max_size
+        */
+       data = (char *)major_collector.alloc_heap (max_size, max_size);
+       sgen_update_heap_boundaries ((mword)data, (mword)(data + max_size));
+       nursery_section->data = data;
+       nursery_section->end_data = data + min_size;
+       scan_starts = (max_size + SCAN_START_SIZE - 1) / SCAN_START_SIZE;
+       nursery_section->scan_starts = (char **)sgen_alloc_internal_dynamic (sizeof (char*) * scan_starts, INTERNAL_MEM_SCAN_STARTS, TRUE);
+       nursery_section->num_scan_start = scan_starts;
 
-       sgen_nursery_allocator_set_nursery_bounds (data, data + sgen_nursery_size);
+       sgen_nursery_allocator_set_nursery_bounds (data, min_size, max_size);
 }
 
 FILE *
@@ -1233,6 +1269,8 @@ init_stats (void)
        mono_counters_register ("Minor fragment clear", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_pre_collection_fragment_clear);
        mono_counters_register ("Minor pinning", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_pinning);
        mono_counters_register ("Minor scan remembered set", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_remsets);
+       mono_counters_register ("Minor scan major blocks", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_major_blocks);
+       mono_counters_register ("Minor scan los", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_los);
        mono_counters_register ("Minor scan pinned", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_pinned);
        mono_counters_register ("Minor scan roots", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_roots);
        mono_counters_register ("Minor fragment creation", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_fragment_creation);
@@ -1330,13 +1368,17 @@ scan_copy_context_for_scan_job (void *worker_data_untyped, ScanJob *job)
 {
        WorkerData *worker_data = (WorkerData *)worker_data_untyped;
 
-       return CONTEXT_FROM_OBJECT_OPERATIONS (job->ops, sgen_workers_get_job_gray_queue (worker_data, job->gc_thread_gray_queue));
-}
+       if (!job->ops) {
+               /*
+                * For jobs enqueued on workers we set the ops at job runtime in order
+                * to be able to profit from on the fly optimized object ops or other
+                * object ops changes, like forced concurrent finish.
+                */
+               SGEN_ASSERT (0, sgen_workers_is_worker_thread (mono_native_thread_id_get ()), "We need a context for the scan job");
+               job->ops = sgen_workers_get_idle_func_object_ops ();
+       }
 
-static void
-job_remembered_set_scan (void *worker_data_untyped, SgenThreadPoolJob *job)
-{
-       remset.scan_remsets (scan_copy_context_for_scan_job (worker_data_untyped, (ScanJob*)job));
+       return CONTEXT_FROM_OBJECT_OPERATIONS (job->ops, sgen_workers_get_job_gray_queue (worker_data, job->gc_thread_gray_queue));
 }
 
 typedef struct {
@@ -1384,6 +1426,43 @@ job_scan_finalizer_entries (void *worker_data_untyped, SgenThreadPoolJob *job)
        scan_finalizer_entries (job_data->queue, ctx);
 }
 
+static void
+job_scan_wbroots (void *worker_data_untyped, SgenThreadPoolJob *job)
+{
+       ScanJob *job_data = (ScanJob*)job;
+       ScanCopyContext ctx = scan_copy_context_for_scan_job (worker_data_untyped, job_data);
+
+       sgen_wbroots_scan_card_table (ctx);
+}
+
+static void
+job_scan_major_card_table (void *worker_data_untyped, SgenThreadPoolJob *job)
+{
+       SGEN_TV_DECLARE (atv);
+       SGEN_TV_DECLARE (btv);
+       ParallelScanJob *job_data = (ParallelScanJob*)job;
+       ScanCopyContext ctx = scan_copy_context_for_scan_job (worker_data_untyped, (ScanJob*)job_data);
+
+       SGEN_TV_GETTIME (atv);
+       major_collector.scan_card_table (CARDTABLE_SCAN_GLOBAL, ctx, job_data->job_index, sgen_workers_get_job_split_count ());
+       SGEN_TV_GETTIME (btv);
+       time_minor_scan_major_blocks += SGEN_TV_ELAPSED (atv, btv);
+}
+
+static void
+job_scan_los_card_table (void *worker_data_untyped, SgenThreadPoolJob *job)
+{
+       SGEN_TV_DECLARE (atv);
+       SGEN_TV_DECLARE (btv);
+       ParallelScanJob *job_data = (ParallelScanJob*)job;
+       ScanCopyContext ctx = scan_copy_context_for_scan_job (worker_data_untyped, (ScanJob*)job_data);
+
+       SGEN_TV_GETTIME (atv);
+       sgen_los_scan_card_table (CARDTABLE_SCAN_GLOBAL, ctx, job_data->job_index, sgen_workers_get_job_split_count ());
+       SGEN_TV_GETTIME (btv);
+       time_minor_scan_los += SGEN_TV_ELAPSED (atv, btv);
+}
+
 static void
 job_scan_major_mod_union_card_table (void *worker_data_untyped, SgenThreadPoolJob *job)
 {
@@ -1447,7 +1526,6 @@ workers_finish_callback (void)
        /* Mod union preclean jobs */
        for (i = 0; i < split_count; i++) {
                psj = (ParallelScanJob*)sgen_thread_pool_job_alloc ("preclean major mod union cardtable", job_major_mod_union_preclean, sizeof (ParallelScanJob));
-               psj->scan_job.ops = sgen_workers_get_idle_func_object_ops ();
                psj->scan_job.gc_thread_gray_queue = NULL;
                psj->job_index = i;
                sgen_workers_enqueue_job (&psj->scan_job.job, TRUE);
@@ -1455,14 +1533,12 @@ workers_finish_callback (void)
 
        for (i = 0; i < split_count; i++) {
                psj = (ParallelScanJob*)sgen_thread_pool_job_alloc ("preclean los mod union cardtable", job_los_mod_union_preclean, sizeof (ParallelScanJob));
-               psj->scan_job.ops = sgen_workers_get_idle_func_object_ops ();
                psj->scan_job.gc_thread_gray_queue = NULL;
                psj->job_index = i;
                sgen_workers_enqueue_job (&psj->scan_job.job, TRUE);
        }
 
        sj = (ScanJob*)sgen_thread_pool_job_alloc ("scan last pinned", job_scan_last_pinned, sizeof (ScanJob));
-       sj->ops = sgen_workers_get_idle_func_object_ops ();
        sj->gc_thread_gray_queue = NULL;
        sgen_workers_enqueue_job (&sj->job, TRUE);
 }
@@ -1475,6 +1551,34 @@ init_gray_queue (SgenGrayQueue *gc_thread_gray_queue, gboolean use_workers)
        sgen_gray_object_queue_init (gc_thread_gray_queue, NULL, TRUE);
 }
 
+static void
+enqueue_scan_remembered_set_jobs (SgenGrayQueue *gc_thread_gray_queue, SgenObjectOperations *ops, gboolean enqueue)
+{
+       int i, split_count = sgen_workers_get_job_split_count ();
+       ScanJob *sj;
+
+       sj = (ScanJob*)sgen_thread_pool_job_alloc ("scan wbroots", job_scan_wbroots, sizeof (ScanJob));
+       sj->ops = ops;
+       sj->gc_thread_gray_queue = gc_thread_gray_queue;
+       sgen_workers_enqueue_job (&sj->job, enqueue);
+
+       for (i = 0; i < split_count; i++) {
+               ParallelScanJob *psj;
+
+               psj = (ParallelScanJob*)sgen_thread_pool_job_alloc ("scan major remsets", job_scan_major_card_table, sizeof (ParallelScanJob));
+               psj->scan_job.ops = ops;
+               psj->scan_job.gc_thread_gray_queue = gc_thread_gray_queue;
+               psj->job_index = i;
+               sgen_workers_enqueue_job (&psj->scan_job.job, enqueue);
+
+               psj = (ParallelScanJob*)sgen_thread_pool_job_alloc ("scan LOS remsets", job_scan_los_card_table, sizeof (ParallelScanJob));
+               psj->scan_job.ops = ops;
+               psj->scan_job.gc_thread_gray_queue = gc_thread_gray_queue;
+               psj->job_index = i;
+               sgen_workers_enqueue_job (&psj->scan_job.job, enqueue);
+       }
+}
+
 static void
 enqueue_scan_from_roots_jobs (SgenGrayQueue *gc_thread_gray_queue, char *heap_start, char *heap_end, SgenObjectOperations *ops, gboolean enqueue)
 {
@@ -1535,13 +1639,10 @@ enqueue_scan_from_roots_jobs (SgenGrayQueue *gc_thread_gray_queue, char *heap_st
 static gboolean
 collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_queue)
 {
-       gboolean needs_major;
-       size_t max_garbage_amount;
-       char *nursery_next;
+       gboolean needs_major, is_parallel = FALSE;
        mword fragment_total;
-       ScanJob *sj;
        SgenGrayQueue gc_thread_gray_queue;
-       SgenObjectOperations *object_ops;
+       SgenObjectOperations *object_ops_nopar, *object_ops_par = NULL;
        ScanCopyContext ctx;
        TV_DECLARE (atv);
        TV_DECLARE (btv);
@@ -1556,10 +1657,16 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
 
        binary_protocol_collection_begin (gc_stats.minor_gc_count, GENERATION_NURSERY);
 
-       if (sgen_concurrent_collection_in_progress ())
-               object_ops = &sgen_minor_collector.serial_ops_with_concurrent_major;
-       else
-               object_ops = &sgen_minor_collector.serial_ops;
+       if (sgen_concurrent_collection_in_progress ()) {
+               /* FIXME Support parallel nursery collections with concurrent major */
+               object_ops_nopar = &sgen_minor_collector.serial_ops_with_concurrent_major;
+       } else {
+               object_ops_nopar = &sgen_minor_collector.serial_ops;
+               if (sgen_minor_collector.is_parallel && sgen_nursery_size >= SGEN_PARALLEL_MINOR_MIN_NURSERY_SIZE) {
+                       object_ops_par = &sgen_minor_collector.parallel_ops;
+                       is_parallel = TRUE;
+               }
+       }
 
        if (do_verify_nursery || do_dump_nursery_content)
                sgen_debug_verify_nursery (do_dump_nursery_content);
@@ -1576,13 +1683,8 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
 
        degraded_mode = 0;
        objects_pinned = 0;
-       nursery_next = sgen_nursery_alloc_get_upper_alloc_bound ();
-       /* FIXME: optimize later to use the higher address where an object can be present */
-       nursery_next = MAX (nursery_next, sgen_get_nursery_end ());
 
-       SGEN_LOG (1, "Start nursery collection %d %p-%p, size: %d", gc_stats.minor_gc_count, sgen_get_nursery_start (), nursery_next, (int)(nursery_next - sgen_get_nursery_start ()));
-       max_garbage_amount = nursery_next - sgen_get_nursery_start ();
-       g_assert (nursery_section->size >= max_garbage_amount);
+       SGEN_LOG (1, "Start nursery collection %d %p-%p, size: %d", gc_stats.minor_gc_count, nursery_section->data, nursery_section->end_data, (int)(nursery_section->end_data - nursery_section->data));
 
        /* world must be stopped already */
        TV_GETTIME (btv);
@@ -1590,14 +1692,12 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
 
        sgen_client_pre_collection_checks ();
 
-       nursery_section->next_data = nursery_next;
-
        major_collector.start_nursery_collection ();
 
        sgen_memgov_minor_collection_start ();
 
-       init_gray_queue (&gc_thread_gray_queue, FALSE);
-       ctx = CONTEXT_FROM_OBJECT_OPERATIONS (object_ops, &gc_thread_gray_queue);
+       init_gray_queue (&gc_thread_gray_queue, is_parallel);
+       ctx = CONTEXT_FROM_OBJECT_OPERATIONS (object_ops_nopar, &gc_thread_gray_queue);
 
        gc_stats.minor_gc_count ++;
 
@@ -1606,7 +1706,7 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
        /* pin from pinned handles */
        sgen_init_pinning ();
        sgen_client_binary_protocol_mark_start (GENERATION_NURSERY);
-       pin_from_roots (sgen_get_nursery_start (), nursery_next, ctx);
+       pin_from_roots (nursery_section->data, nursery_section->end_data, ctx);
        /* pin cemented objects */
        sgen_pin_cemented_objects ();
        /* identify pinned objects */
@@ -1629,10 +1729,9 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
        SGEN_LOG (2, "Finding pinned pointers: %zd in %lld usecs", sgen_get_pinned_count (), (long long)TV_ELAPSED (btv, atv));
        SGEN_LOG (4, "Start scan with %zd pinned objects", sgen_get_pinned_count ());
 
-       sj = (ScanJob*)sgen_thread_pool_job_alloc ("scan remset", job_remembered_set_scan, sizeof (ScanJob));
-       sj->ops = object_ops;
-       sj->gc_thread_gray_queue = &gc_thread_gray_queue;
-       sgen_workers_enqueue_job (&sj->job, FALSE);
+       remset.start_scan_remsets ();
+
+       enqueue_scan_remembered_set_jobs (&gc_thread_gray_queue, is_parallel ? NULL : object_ops_nopar, is_parallel);
 
        /* we don't have complete write barrier yet, so we scan all the old generation sections */
        TV_GETTIME (btv);
@@ -1647,7 +1746,13 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
        TV_GETTIME (atv);
        time_minor_scan_pinned += TV_ELAPSED (btv, atv);
 
-       enqueue_scan_from_roots_jobs (&gc_thread_gray_queue, sgen_get_nursery_start (), nursery_next, object_ops, FALSE);
+       enqueue_scan_from_roots_jobs (&gc_thread_gray_queue, nursery_section->data, nursery_section->end_data, is_parallel ? NULL : object_ops_nopar, is_parallel);
+
+       if (is_parallel) {
+               gray_queue_redirect (&gc_thread_gray_queue);
+               sgen_workers_start_all_workers (object_ops_nopar, object_ops_par, NULL);
+               sgen_workers_join ();
+       }
 
        TV_GETTIME (btv);
        time_minor_scan_roots += TV_ELAPSED (atv, btv);
@@ -1670,6 +1775,20 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
        if (remset_consistency_checks)
                sgen_check_remset_consistency ();
 
+
+       if (sgen_max_pause_time) {
+               int duration;
+
+               TV_GETTIME (btv);
+               duration = (int)(TV_ELAPSED (last_minor_collection_start_tv, btv) / 10000);
+               if (duration > (sgen_max_pause_time * sgen_max_pause_margin))
+                       sgen_resize_nursery (TRUE);
+               else
+                       sgen_resize_nursery (FALSE);
+       } else {
+                       sgen_resize_nursery (FALSE);
+       }
+
        /* walk the pin_queue, build up the fragment list of free memory, unmark
         * pinned objects as we go, memzero() the empty fragments so they are ready for the
         * next allocations.
@@ -1709,8 +1828,6 @@ collect_nursery (const char *reason, gboolean is_overflow, SgenGrayQueue *unpin_
 
        sgen_gray_object_queue_dispose (&gc_thread_gray_queue);
 
-       remset.finish_minor_collection ();
-
        check_scan_starts ();
 
        binary_protocol_flush_buffers (FALSE);
@@ -1774,12 +1891,6 @@ major_copy_or_mark_from_roots (SgenGrayQueue *gc_thread_gray_queue, size_t *old_
        TV_GETTIME (btv);
        time_major_pre_collection_fragment_clear += TV_ELAPSED (atv, btv);
 
-       if (!sgen_collection_is_concurrent ())
-               nursery_section->next_data = sgen_get_nursery_end ();
-       /* we should also coalesce scanning from sections close to each other
-        * and deal with pointers outside of the sections later.
-        */
-
        objects_pinned = 0;
 
        sgen_client_pre_collection_checks ();
@@ -1867,7 +1978,8 @@ major_copy_or_mark_from_roots (SgenGrayQueue *gc_thread_gray_queue, size_t *old_
 
        SGEN_ASSERT (0, sgen_workers_all_done (), "Why are the workers not done when we start or finish a major collection?");
        if (mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT) {
-               sgen_workers_set_num_active_workers (0);
+               if (object_ops_par != NULL)
+                       sgen_workers_set_num_active_workers (0);
                if (sgen_workers_have_idle_work ()) {
                        /*
                         * We force the finish of the worker with the new object ops context
@@ -1912,36 +2024,41 @@ major_copy_or_mark_from_roots (SgenGrayQueue *gc_thread_gray_queue, size_t *old_
 
        if (mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT) {
                int i, split_count = sgen_workers_get_job_split_count ();
+               gboolean parallel = object_ops_par != NULL;
 
-               gray_queue_redirect (gc_thread_gray_queue);
+               /* If we're not parallel we finish the collection on the gc thread */
+               if (parallel)
+                       gray_queue_redirect (gc_thread_gray_queue);
 
                /* Mod union card table */
                for (i = 0; i < split_count; i++) {
                        ParallelScanJob *psj;
 
                        psj = (ParallelScanJob*)sgen_thread_pool_job_alloc ("scan mod union cardtable", job_scan_major_mod_union_card_table, sizeof (ParallelScanJob));
-                       psj->scan_job.ops = object_ops_par ? object_ops_par : object_ops_nopar;
-                       psj->scan_job.gc_thread_gray_queue = NULL;
+                       psj->scan_job.ops = parallel ? NULL : object_ops_nopar;
+                       psj->scan_job.gc_thread_gray_queue = gc_thread_gray_queue;
                        psj->job_index = i;
-                       sgen_workers_enqueue_job (&psj->scan_job.job, TRUE);
+                       sgen_workers_enqueue_job (&psj->scan_job.job, parallel);
 
                        psj = (ParallelScanJob*)sgen_thread_pool_job_alloc ("scan LOS mod union cardtable", job_scan_los_mod_union_card_table, sizeof (ParallelScanJob));
-                       psj->scan_job.ops = object_ops_par ? object_ops_par : object_ops_nopar;
-                       psj->scan_job.gc_thread_gray_queue = NULL;
+                       psj->scan_job.ops = parallel ? NULL : object_ops_nopar;
+                       psj->scan_job.gc_thread_gray_queue = gc_thread_gray_queue;
                        psj->job_index = i;
-                       sgen_workers_enqueue_job (&psj->scan_job.job, TRUE);
+                       sgen_workers_enqueue_job (&psj->scan_job.job, parallel);
                }
 
-               /*
-                * If we enqueue a job while workers are running we need to sgen_workers_ensure_awake
-                * in order to make sure that we are running the idle func and draining all worker
-                * gray queues. The operation of starting workers implies this, so we start them after
-                * in order to avoid doing this operation twice. The workers will drain the main gray
-                * stack that contained roots and pinned objects and also scan the mod union card
-                * table.
-                */
-               sgen_workers_start_all_workers (object_ops_nopar, object_ops_par, NULL);
-               sgen_workers_join ();
+               if (parallel) {
+                       /*
+                        * If we enqueue a job while workers are running we need to sgen_workers_ensure_awake
+                        * in order to make sure that we are running the idle func and draining all worker
+                        * gray queues. The operation of starting workers implies this, so we start them after
+                        * in order to avoid doing this operation twice. The workers will drain the main gray
+                        * stack that contained roots and pinned objects and also scan the mod union card
+                        * table.
+                        */
+                       sgen_workers_start_all_workers (object_ops_nopar, object_ops_par, NULL);
+                       sgen_workers_join ();
+               }
        }
 
        sgen_pin_stats_report ();
@@ -2834,21 +2951,9 @@ mono_gc_wbarrier_generic_store_atomic (gpointer ptr, GCObject *value)
 }
 
 void
-sgen_wbarrier_value_copy_bitmap (gpointer _dest, gpointer _src, int size, unsigned bitmap)
+sgen_wbarrier_range_copy (gpointer _dest, gpointer _src, int size)
 {
-       GCObject **dest = (GCObject **)_dest;
-       GCObject **src = (GCObject **)_src;
-
-       while (size) {
-               if (bitmap & 0x1)
-                       mono_gc_wbarrier_generic_store (dest, *src);
-               else
-                       *dest = *src;
-               ++src;
-               ++dest;
-               size -= SIZEOF_VOID_P;
-               bitmap >>= 1;
-       }
+       remset.wbarrier_range_copy (_dest,_src, size);
 }
 
 /*
@@ -2881,7 +2986,7 @@ sgen_gc_get_used_size (void)
        gint64 tot = 0;
        LOCK_GC;
        tot = los_memory_usage;
-       tot += nursery_section->next_data - nursery_section->data;
+       tot += nursery_section->end_data - nursery_section->data;
        tot += major_collector.get_used_size ();
        /* FIXME: account for pinned objects */
        UNLOCK_GC;
@@ -2921,13 +3026,162 @@ parse_double_in_interval (const char *env_var, const char *opt_name, const char
        return TRUE;
 }
 
+static SgenMinor
+parse_sgen_minor (const char *opt)
+{
+       if (!opt)
+               return SGEN_MINOR_DEFAULT;
+
+       if (!strcmp (opt, "simple")) {
+               return SGEN_MINOR_SIMPLE;
+       } else if (!strcmp (opt, "simple-par")) {
+               return SGEN_MINOR_SIMPLE_PARALLEL;
+       } else if (!strcmp (opt, "split")) {
+               return SGEN_MINOR_SPLIT;
+       } else {
+               sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default instead.", "Unknown minor collector `%s'.", opt);
+               return SGEN_MINOR_DEFAULT;
+       }
+}
+
+static SgenMajor
+parse_sgen_major (const char *opt)
+{
+       if (!opt)
+               return SGEN_MAJOR_DEFAULT;
+
+       if (!strcmp (opt, "marksweep")) {
+               return SGEN_MAJOR_SERIAL;
+       } else if (!strcmp (opt, "marksweep-conc")) {
+               return SGEN_MAJOR_CONCURRENT;
+       } else if (!strcmp (opt, "marksweep-conc-par")) {
+               return SGEN_MAJOR_CONCURRENT_PARALLEL;
+       } else {
+               sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default instead.", "Unknown major collector `%s'.", opt);
+               return SGEN_MAJOR_DEFAULT;
+       }
+
+}
+
+static SgenMode
+parse_sgen_mode (const char *opt)
+{
+       if (!opt)
+               return SGEN_MODE_NONE;
+
+       if (!strcmp (opt, "balanced")) {
+               return SGEN_MODE_BALANCED;
+       } else if (!strcmp (opt, "throughput")) {
+               return SGEN_MODE_THROUGHPUT;
+       } else if (!strcmp (opt, "pause") || g_str_has_prefix (opt, "pause:")) {
+               return SGEN_MODE_PAUSE;
+       } else {
+               sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default configurations.", "Unknown mode `%s'.", opt);
+               return SGEN_MODE_NONE;
+       }
+}
+
+static void
+init_sgen_minor (SgenMinor minor)
+{
+       switch (minor) {
+       case SGEN_MINOR_DEFAULT:
+       case SGEN_MINOR_SIMPLE:
+               sgen_simple_nursery_init (&sgen_minor_collector, FALSE);
+               break;
+       case SGEN_MINOR_SIMPLE_PARALLEL:
+               sgen_simple_nursery_init (&sgen_minor_collector, TRUE);
+               break;
+       case SGEN_MINOR_SPLIT:
+               sgen_split_nursery_init (&sgen_minor_collector);
+               break;
+       default:
+               g_assert_not_reached ();
+       }
+}
+
+static void
+init_sgen_major (SgenMajor major)
+{
+       if (major == SGEN_MAJOR_DEFAULT)
+               major = DEFAULT_MAJOR;
+
+       switch (major) {
+       case SGEN_MAJOR_SERIAL:
+               sgen_marksweep_init (&major_collector);
+               break;
+       case SGEN_MAJOR_CONCURRENT:
+               sgen_marksweep_conc_init (&major_collector);
+               break;
+       case SGEN_MAJOR_CONCURRENT_PARALLEL:
+               sgen_marksweep_conc_par_init (&major_collector);
+               break;
+       default:
+               g_assert_not_reached ();
+       }
+}
+
+/*
+ * If sgen mode is set, major/minor configuration is fixed. The other gc_params
+ * are parsed and processed after major/minor initialization, so it can potentially
+ * override some knobs set by the sgen mode. We can consider locking out additional
+ * configurations when gc_modes are used.
+ */
+static void
+init_sgen_mode (SgenMode mode)
+{
+       SgenMinor minor = SGEN_MINOR_DEFAULT;
+       SgenMajor major = SGEN_MAJOR_DEFAULT;
+
+       switch (mode) {
+       case SGEN_MODE_BALANCED:
+               /*
+                * Use a dynamic parallel nursery with a major concurrent collector.
+                * This uses the default values for max pause time and nursery size.
+                */
+               minor = SGEN_MINOR_SIMPLE;
+               major = SGEN_MAJOR_CONCURRENT;
+               dynamic_nursery = TRUE;
+               break;
+       case SGEN_MODE_THROUGHPUT:
+               /*
+                * Use concurrent major to let the mutator do more work. Use a larger
+                * nursery, without pause time constraints, in order to collect more
+                * objects in parallel and avoid repetitive collection tasks (pinning,
+                * root scanning etc)
+                */
+               minor = SGEN_MINOR_SIMPLE_PARALLEL;
+               major = SGEN_MAJOR_CONCURRENT;
+               dynamic_nursery = TRUE;
+               sgen_max_pause_time = 0;
+               break;
+       case SGEN_MODE_PAUSE:
+               /*
+                * Use concurrent major and dynamic nursery with a more
+                * aggressive shrinking relative to pause times.
+                * FIXME use parallel minors
+                */
+               minor = SGEN_MINOR_SIMPLE;
+               major = SGEN_MAJOR_CONCURRENT;
+               dynamic_nursery = TRUE;
+               sgen_max_pause_margin = SGEN_PAUSE_MODE_MAX_PAUSE_MARGIN;
+               break;
+       default:
+               g_assert_not_reached ();
+       }
+
+       init_sgen_minor (minor);
+       init_sgen_major (major);
+}
+
 void
 sgen_gc_init (void)
 {
-       const char *env;
+       char *env;
        char **opts, **ptr;
-       char *major_collector_opt = NULL;
-       char *minor_collector_opt = NULL;
+       SgenMajor sgen_major = SGEN_MAJOR_DEFAULT;
+       SgenMinor sgen_minor = SGEN_MINOR_DEFAULT;
+       SgenMode sgen_mode = SGEN_MODE_NONE;
        char *params_opts = NULL;
        char *debug_opts = NULL;
        size_t max_heap = 0;
@@ -2969,6 +3223,7 @@ sgen_gc_init (void)
 
        if ((env = g_getenv (MONO_GC_PARAMS_NAME)) || gc_params_options) {
                params_opts = g_strdup_printf ("%s,%s", gc_params_options ? gc_params_options : "", env ? env : "");
+               g_free (env);
        }
 
        if (params_opts) {
@@ -2977,10 +3232,13 @@ sgen_gc_init (void)
                        char *opt = *ptr;
                        if (g_str_has_prefix (opt, "major=")) {
                                opt = strchr (opt, '=') + 1;
-                               major_collector_opt = g_strdup (opt);
+                               sgen_major = parse_sgen_major (opt);
                        } else if (g_str_has_prefix (opt, "minor=")) {
                                opt = strchr (opt, '=') + 1;
-                               minor_collector_opt = g_strdup (opt);
+                               sgen_minor = parse_sgen_minor (opt);
+                       } else if (g_str_has_prefix (opt, "mode=")) {
+                               opt = strchr (opt, '=') + 1;
+                               sgen_mode = parse_sgen_mode (opt);
                        }
                }
        } else {
@@ -3002,36 +3260,15 @@ sgen_gc_init (void)
 
        sgen_client_init ();
 
-       if (!minor_collector_opt) {
-               sgen_simple_nursery_init (&sgen_minor_collector);
+       if (sgen_mode != SGEN_MODE_NONE) {
+               if (sgen_minor != SGEN_MINOR_DEFAULT || sgen_major != SGEN_MAJOR_DEFAULT)
+                       sgen_env_var_error (MONO_GC_PARAMS_NAME, "Ignoring major/minor configuration", "Major/minor configurations cannot be used with sgen modes");
+               init_sgen_mode (sgen_mode);
        } else {
-               if (!strcmp (minor_collector_opt, "simple")) {
-               use_simple_nursery:
-                       sgen_simple_nursery_init (&sgen_minor_collector);
-               } else if (!strcmp (minor_collector_opt, "split")) {
-                       sgen_split_nursery_init (&sgen_minor_collector);
-               } else {
-                       sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using `simple` instead.", "Unknown minor collector `%s'.", minor_collector_opt);
-                       goto use_simple_nursery;
-               }
+               init_sgen_minor (sgen_minor);
+               init_sgen_major (sgen_major);
        }
 
-       if (!major_collector_opt) {
-       use_default_major:
-               DEFAULT_MAJOR_INIT (&major_collector);
-       } else if (!strcmp (major_collector_opt, "marksweep")) {
-               sgen_marksweep_init (&major_collector);
-       } else if (!strcmp (major_collector_opt, "marksweep-conc")) {
-               sgen_marksweep_conc_init (&major_collector);
-       } else if (!strcmp (major_collector_opt, "marksweep-conc-par")) {
-               sgen_marksweep_conc_par_init (&major_collector);
-       } else {
-               sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using `" DEFAULT_MAJOR_NAME "` instead.", "Unknown major collector `%s'.", major_collector_opt);
-               goto use_default_major;
-       }
-
-       sgen_nursery_size = DEFAULT_NURSERY_SIZE;
-
        if (opts) {
                gboolean usage_printed = FALSE;
 
@@ -3043,6 +3280,17 @@ sgen_gc_init (void)
                                continue;
                        if (g_str_has_prefix (opt, "minor="))
                                continue;
+                       if (g_str_has_prefix (opt, "mode=")) {
+                               if (g_str_has_prefix (opt, "mode=pause:")) {
+                                       char *str_pause = strchr (opt, ':') + 1;
+                                       int pause = atoi (str_pause);
+                                       if (pause)
+                                               sgen_max_pause_time = pause;
+                                       else
+                                               sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default", "Invalid maximum pause time for `pause` sgen mode");
+                               }
+                               continue;
+                       }
                        if (g_str_has_prefix (opt, "max-heap-size=")) {
                                size_t page_size = mono_pagesize ();
                                size_t max_heap_candidate = 0;
@@ -3068,8 +3316,6 @@ sgen_gc_init (void)
                                }
                                continue;
                        }
-
-#ifdef USER_CONFIG
                        if (g_str_has_prefix (opt, "nursery-size=")) {
                                size_t val;
                                opt = strchr (opt, '=') + 1;
@@ -3085,17 +3331,14 @@ sgen_gc_init (void)
                                                continue;
                                        }
 
-                                       sgen_nursery_size = val;
-                                       sgen_nursery_bits = 0;
-                                       while (ONE_P << (++ sgen_nursery_bits) != sgen_nursery_size)
-                                               ;
+                                       min_nursery_size = max_nursery_size = val;
+                                       dynamic_nursery = FALSE;
                                } else {
                                        sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default value.", "`nursery-size` must be an integer.");
                                        continue;
                                }
                                continue;
                        }
-#endif
                        if (g_str_has_prefix (opt, "save-target-ratio=")) {
                                double val;
                                opt = strchr (opt, '=') + 1;
@@ -3133,6 +3376,19 @@ sgen_gc_init (void)
                                continue;
                        }
 
+                       if (!strcmp (opt, "dynamic-nursery")) {
+                               if (sgen_minor_collector.is_split)
+                                       sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default value.",
+                                                       "dynamic-nursery not supported with split-nursery.");
+                               else
+                                       dynamic_nursery = TRUE;
+                               continue;
+                       }
+                       if (!strcmp (opt, "no-dynamic-nursery")) {
+                               dynamic_nursery = FALSE;
+                               continue;
+                       }
+
                        if (major_collector.handle_gc_param && major_collector.handle_gc_param (opt))
                                continue;
 
@@ -3150,11 +3406,13 @@ sgen_gc_init (void)
                        fprintf (stderr, "\n%s must be a comma-delimited list of one or more of the following:\n", MONO_GC_PARAMS_NAME);
                        fprintf (stderr, "  max-heap-size=N (where N is an integer, possibly with a k, m or a g suffix)\n");
                        fprintf (stderr, "  soft-heap-limit=n (where N is an integer, possibly with a k, m or a g suffix)\n");
+                       fprintf (stderr, "  mode=MODE (where MODE is 'balanced', 'throughput' or 'pause[:N]' and N is maximum pause in milliseconds)\n");
                        fprintf (stderr, "  nursery-size=N (where N is an integer, possibly with a k, m or a g suffix)\n");
                        fprintf (stderr, "  major=COLLECTOR (where COLLECTOR is `marksweep', `marksweep-conc', `marksweep-par')\n");
                        fprintf (stderr, "  minor=COLLECTOR (where COLLECTOR is `simple' or `split')\n");
                        fprintf (stderr, "  wbarrier=WBARRIER (where WBARRIER is `remset' or `cardtable')\n");
                        fprintf (stderr, "  [no-]cementing\n");
+                       fprintf (stderr, "  [no-]dynamic-nursery\n");
                        if (major_collector.print_gc_param_usage)
                                major_collector.print_gc_param_usage ();
                        if (sgen_minor_collector.print_gc_param_usage)
@@ -3170,22 +3428,17 @@ sgen_gc_init (void)
                g_strfreev (opts);
        }
 
-       if (major_collector_opt)
-               g_free (major_collector_opt);
-
-       if (minor_collector_opt)
-               g_free (minor_collector_opt);
-
        if (params_opts)
                g_free (params_opts);
 
-       alloc_nursery ();
+       alloc_nursery (dynamic_nursery, min_nursery_size, max_nursery_size);
 
        sgen_pinning_init ();
        sgen_cement_init (cement_enabled);
 
        if ((env = g_getenv (MONO_GC_DEBUG_NAME)) || gc_debug_options) {
                debug_opts = g_strdup_printf ("%s,%s", gc_debug_options ? gc_debug_options  : "", env ? env : "");
+               g_free (env);
        }
 
        if (debug_opts) {
@@ -3215,6 +3468,15 @@ sgen_gc_init (void)
                        } else if (!strcmp (opt, "verify-before-allocs")) {
                                verify_before_allocs = 1;
                                has_per_allocation_action = TRUE;
+                       } else if (g_str_has_prefix (opt, "max-valloc-size=")) {
+                               size_t max_valloc_size;
+                               char *arg = strchr (opt, '=') + 1;
+                               if (*opt && mono_gc_parse_environment_string_extract_number (arg, &max_valloc_size)) {
+                                       mono_valloc_set_limit (max_valloc_size);
+                               } else {
+                                       sgen_env_var_error (MONO_GC_DEBUG_NAME, NULL, "`max-valloc-size` must be an integer.");
+                               }
+                               continue;
                        } else if (g_str_has_prefix (opt, "verify-before-allocs=")) {
                                char *arg = strchr (opt, '=') + 1;
                                verify_before_allocs = atoi (arg);
@@ -3295,6 +3557,7 @@ sgen_gc_init (void)
                                fprintf (stderr, "Valid <option>s are:\n");
                                fprintf (stderr, "  collect-before-allocs[=<n>]\n");
                                fprintf (stderr, "  verify-before-allocs[=<n>]\n");
+                               fprintf (stderr, "  max-valloc-size=N (where N is an integer, possibly with a k, m or a g suffix)\n");
                                fprintf (stderr, "  check-remset-consistency\n");
                                fprintf (stderr, "  check-mark-bits\n");
                                fprintf (stderr, "  check-nursery-pinned\n");
@@ -3331,15 +3594,18 @@ sgen_gc_init (void)
        if (major_collector.post_param_init)
                major_collector.post_param_init (&major_collector);
 
-       if (major_collector.needs_thread_pool) {
+       if (major_collector.is_concurrent || sgen_minor_collector.is_parallel) {
                int num_workers = 1;
-               if (major_collector.is_parallel) {
-                       /* FIXME Detect the number of physical cores, instead of logical */
-                       num_workers = mono_cpu_count () / 2;
-                       if (num_workers < 1)
+               if (major_collector.is_parallel || sgen_minor_collector.is_parallel) {
+                       num_workers = mono_cpu_count ();
+                       if (num_workers <= 1) {
                                num_workers = 1;
+                               major_collector.is_parallel = FALSE;
+                               sgen_minor_collector.is_parallel = FALSE;
+                       }
                }
-               sgen_workers_init (num_workers, (SgenWorkerCallback) major_collector.worker_init_cb);
+               if (major_collector.is_concurrent || sgen_minor_collector.is_parallel)
+                       sgen_workers_init (num_workers, (SgenWorkerCallback) major_collector.worker_init_cb);
        }
 
        sgen_memgov_init (max_heap, soft_limit, debug_print_allowance, allowance_ratio, save_target);
@@ -3397,6 +3663,12 @@ sgen_get_major_collector (void)
        return &major_collector;
 }
 
+SgenMinorCollector*
+sgen_get_minor_collector (void)
+{
+       return &sgen_minor_collector;
+}
+
 SgenRememberedSet*
 sgen_get_remset (void)
 {