Lazier zero_dirty_pages in gencgc
[sbcl.git] / src / runtime / gencgc.c
index 9680743..be5cc4b 100644 (file)
@@ -41,6 +41,7 @@
 #include "gc.h"
 #include "gc-internal.h"
 #include "thread.h"
+#include "pseudo-atomic.h"
 #include "alloc.h"
 #include "genesis/vector.h"
 #include "genesis/weak-pointer.h"
@@ -54,6 +55,9 @@
 #if defined(LUTEX_WIDETAG)
 #include "pthread-lutex.h"
 #endif
+#if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
+#include "genesis/cons.h"
+#endif
 
 /* forward declarations */
 page_index_t  gc_find_freeish_pages(long *restart_page_ptr, long nbytes,
@@ -68,9 +72,7 @@ page_index_t  gc_find_freeish_pages(long *restart_page_ptr, long nbytes,
  * scratch space by the collector, and should never get collected.
  */
 enum {
-    HIGHEST_NORMAL_GENERATION = 5,
-    PSEUDO_STATIC_GENERATION,
-    SCRATCH_GENERATION,
+    SCRATCH_GENERATION = PSEUDO_STATIC_GENERATION+1,
     NUM_GENERATIONS
 };
 
@@ -88,7 +90,7 @@ long large_object_size = 4 * PAGE_BYTES;
 
 /* the verbosity level. All non-error messages are disabled at level 0;
  * and only a few rare messages are printed at level 1. */
-#ifdef QSHOW
+#if QSHOW
 boolean gencgc_verbose = 1;
 #else
 boolean gencgc_verbose = 0;
@@ -256,7 +258,12 @@ size_t void_diff(void *x, void *y)
     return (pointer_sized_uint_t)x - (pointer_sized_uint_t)y;
 }
 
-/* a structure to hold the state of a generation */
+/* a structure to hold the state of a generation
+ *
+ * CAUTION: If you modify this, make sure to touch up the alien
+ * definition in src/code/gc.lisp accordingly. ...or better yes,
+ * deal with the FIXME there...
+ */
 struct generation {
 
     /* the first page that gc_alloc() checks on its next call */
@@ -286,9 +293,9 @@ struct generation {
     /* the number of GCs since the last raise */
     int num_gc;
 
-    /* the average age after which a GC will raise objects to the
+    /* the number of GCs to run on the generations before raising objects to the
      * next generation */
-    int trigger_age;
+    int number_of_gcs_before_promotion;
 
     /* the cumulative sum of the bytes allocated to this generation. It is
      * cleared after a GC on this generations, and update before new
@@ -300,7 +307,7 @@ struct generation {
     /* a minimum average memory age before a GC will occur helps
      * prevent a GC when a large number of new live objects have been
      * added, in which case a GC could be a waste of time */
-    double min_av_mem_age;
+    double minimum_age_before_gc;
 
     /* A linked list of lutex structures in this generation, used for
      * implementing lutex finalization. */
@@ -383,7 +390,7 @@ count_generation_pages(generation_index_t generation)
     return count;
 }
 
-#ifdef QSHOW
+#if QSHOW
 static long
 count_dont_move_pages(void)
 {
@@ -415,8 +422,8 @@ count_generation_bytes_allocated (generation_index_t gen)
 }
 
 /* Return the average age of the memory in a generation. */
-static double
-gen_av_mem_age(generation_index_t gen)
+extern double
+generation_average_age(generation_index_t gen)
 {
     if (generations[gen].bytes_allocated == 0)
         return 0.0;
@@ -426,12 +433,10 @@ gen_av_mem_age(generation_index_t gen)
         / ((double)generations[gen].bytes_allocated);
 }
 
-/* The verbose argument controls how much to print: 0 for normal
- * level of detail; 1 for debugging. */
-static void
-print_generation_stats(int verbose) /* FIXME: should take FILE argument */
+extern void
+write_generation_stats(FILE *file)
 {
-    generation_index_t i, gens;
+    generation_index_t i;
 
 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 #define FPU_STATE_SIZE 27
@@ -445,17 +450,11 @@ print_generation_stats(int verbose) /* FIXME: should take FILE argument */
      * so they need to be saved and reset for C. */
     fpu_save(fpu_state);
 
-    /* highest generation to print */
-    if (verbose)
-        gens = SCRATCH_GENERATION;
-    else
-        gens = PSEUDO_STATIC_GENERATION;
-
     /* Print the heap stats. */
-    fprintf(stderr,
+    fprintf(file,
             " Gen StaPg UbSta LaSta LUbSt Boxed Unboxed LB   LUB  !move  Alloc  Waste   Trig    WP  GCs Mem-age\n");
 
-    for (i = 0; i < gens; i++) {
+    for (i = 0; i < SCRATCH_GENERATION; i++) {
         page_index_t j;
         long boxed_cnt = 0;
         long unboxed_cnt = 0;
@@ -487,7 +486,7 @@ print_generation_stats(int verbose) /* FIXME: should take FILE argument */
 
         gc_assert(generations[i].bytes_allocated
                   == count_generation_bytes_allocated(i));
-        fprintf(stderr,
+        fprintf(file,
                 "   %1d: %5ld %5ld %5ld %5ld %5ld %5ld %5ld %5ld %5ld %8ld %5ld %8ld %4ld %3d %7.4f\n",
                 i,
                 generations[i].alloc_start_page,
@@ -505,13 +504,77 @@ print_generation_stats(int verbose) /* FIXME: should take FILE argument */
                 generations[i].gc_trigger,
                 count_write_protect_generation_pages(i),
                 generations[i].num_gc,
-                gen_av_mem_age(i));
+                generation_average_age(i));
     }
-    fprintf(stderr,"   Total bytes allocated    = %lu\n", bytes_allocated);
-    fprintf(stderr,"   Dynamic-space-size bytes = %u\n", dynamic_space_size);
+    fprintf(file,"   Total bytes allocated    = %lu\n", bytes_allocated);
+    fprintf(file,"   Dynamic-space-size bytes = %lu\n", (unsigned long)dynamic_space_size);
 
     fpu_restore(fpu_state);
 }
+
+extern void
+write_heap_exhaustion_report(FILE *file, long available, long requested,
+                             struct thread *thread)
+{
+    fprintf(file,
+            "Heap exhausted during %s: %ld bytes available, %ld requested.\n",
+            gc_active_p ? "garbage collection" : "allocation",
+            available,
+            requested);
+    write_generation_stats(file);
+    fprintf(file, "GC control variables:\n");
+    fprintf(file, "   *GC-INHIBIT* = %s\n   *GC-PENDING* = %s\n",
+            SymbolValue(GC_INHIBIT,thread)==NIL ? "false" : "true",
+            (SymbolValue(GC_PENDING, thread) == T) ?
+            "true" : ((SymbolValue(GC_PENDING, thread) == NIL) ?
+                      "false" : "in progress"));
+#ifdef LISP_FEATURE_SB_THREAD
+    fprintf(file, "   *STOP-FOR-GC-PENDING* = %s\n",
+            SymbolValue(STOP_FOR_GC_PENDING,thread)==NIL ? "false" : "true");
+#endif
+}
+
+extern void
+print_generation_stats(void)
+{
+    write_generation_stats(stderr);
+}
+
+extern char* gc_logfile;
+char * gc_logfile = NULL;
+
+extern void
+log_generation_stats(char *logfile, char *header)
+{
+    if (logfile) {
+        FILE * log = fopen(logfile, "a");
+        if (log) {
+            fprintf(log, "%s\n", header);
+            write_generation_stats(log);
+            fclose(log);
+        } else {
+            fprintf(stderr, "Could not open gc logfile: %s\n", logfile);
+            fflush(stderr);
+        }
+    }
+}
+
+extern void
+report_heap_exhaustion(long available, long requested, struct thread *th)
+{
+    if (gc_logfile) {
+        FILE * log = fopen(gc_logfile, "a");
+        if (log) {
+            write_heap_exhaustion_report(log, available, requested, th);
+            fclose(log);
+        } else {
+            fprintf(stderr, "Could not open gc logfile: %s\n", gc_logfile);
+            fflush(stderr);
+        }
+    }
+    /* Always to stderr as well. */
+    write_heap_exhaustion_report(stderr, available, requested, th);
+}
 \f
 
 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
@@ -564,13 +627,13 @@ zero_pages(page_index_t start, page_index_t end) {
  */
 static void
 zero_dirty_pages(page_index_t start, page_index_t end) {
-    page_index_t i;
+    page_index_t i, j;
 
     for (i = start; i <= end; i++) {
-        if (page_table[i].need_to_zero == 1) {
-            zero_pages(start, end);
-            break;
-        }
+        if (!page_table[i].need_to_zero) continue;
+        for (j = i+1; (j <= end) && (page_table[j].need_to_zero); j++);
+        zero_pages(i, j-1);
+        i = j;
     }
 
     for (i = start; i <= end; i++) {
@@ -1160,22 +1223,11 @@ gc_heap_exhausted_error_or_lose (long available, long requested)
      * the danger that we bounce back here before the error has been
      * handled, or indeed even printed.
      */
-    fprintf(stderr, "Heap exhausted during %s: %ld bytes available, %ld requested.\n",
-            gc_active_p ? "garbage collection" : "allocation",
-            available, requested);
+    report_heap_exhaustion(available, requested, thread);
     if (gc_active_p || (available == 0)) {
         /* If we are in GC, or totally out of memory there is no way
          * to sanely transfer control to the lisp-side of things.
          */
-        print_generation_stats(1);
-        fprintf(stderr, "GC control variables:\n");
-        fprintf(stderr, "          *GC-INHIBIT* = %s\n          *GC-PENDING* = %s\n",
-                SymbolValue(GC_INHIBIT,thread)==NIL ? "false" : "true",
-                SymbolValue(GC_PENDING,thread)==NIL ? "false" : "true");
-#ifdef LISP_FEATURE_SB_THREAD
-        fprintf(stderr, " *STOP-FOR-GC-PENDING* = %s\n",
-                SymbolValue(STOP_FOR_GC_PENDING,thread)==NIL ? "false" : "true");
-#endif
         lose("Heap exhausted, game over.");
     }
     else {
@@ -1412,15 +1464,11 @@ copy_large_object(lispobj object, long nwords)
             gc_assert(page_table[next_page].region_start_offset ==
                       npage_bytes(next_page-first_page));
             gc_assert(page_table[next_page].bytes_used == PAGE_BYTES);
+            /* Should have been unprotected by unprotect_oldspace(). */
+            gc_assert(page_table[next_page].write_protected == 0);
 
             page_table[next_page].gen = new_space;
 
-            /* Remove any write-protection. We should be able to rely
-             * on the write-protect flag to avoid redundant calls. */
-            if (page_table[next_page].write_protected) {
-                os_protect(page_address(next_page), PAGE_BYTES, OS_VM_PROT_ALL);
-                page_table[next_page].write_protected = 0;
-            }
             remaining_bytes -= PAGE_BYTES;
             next_page++;
         }
@@ -1681,7 +1729,7 @@ sniff_code_object(struct code *code, unsigned long displacement)
         unsigned d2 = *((unsigned char *)p - 2);
         unsigned d3 = *((unsigned char *)p - 3);
         unsigned d4 = *((unsigned char *)p - 4);
-#ifdef QSHOW
+#if QSHOW
         unsigned d5 = *((unsigned char *)p - 5);
         unsigned d6 = *((unsigned char *)p - 6);
 #endif
@@ -2218,8 +2266,6 @@ search_dynamic_space(void *pointer)
                             (lispobj *)pointer));
 }
 
-#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
-
 /* Helper for valid_lisp_pointer_p and
  * possibly_valid_dynamic_space_pointer.
  *
@@ -2241,8 +2287,12 @@ looks_like_valid_lisp_pointer_p(lispobj *pointer, lispobj *start_addr)
          * header. */
         switch (widetag_of(*start_addr)) {
         case CODE_HEADER_WIDETAG:
-            /* This case is probably caught above. */
-            break;
+          /* Make sure we actually point to a function in the code object,
+           * as opposed to a random point there. */
+          if (SIMPLE_FUN_HEADER_WIDETAG==widetag_of(*(pointer-FUN_POINTER_LOWTAG)))
+            return 1;
+          else
+            return 0;
         case CLOSURE_HEADER_WIDETAG:
         case FUNCALLABLE_INSTANCE_HEADER_WIDETAG:
             if ((unsigned long)pointer !=
@@ -2308,6 +2358,23 @@ looks_like_valid_lisp_pointer_p(lispobj *pointer, lispobj *start_addr)
         }
         break;
     case OTHER_POINTER_LOWTAG:
+
+#if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
+        /* The all-architecture test below is good as far as it goes,
+         * but an LRA object is similar to a FUN-POINTER: It is
+         * embedded within a CODE-OBJECT pointed to by start_addr, and
+         * cannot be found by simply walking the heap, therefore we
+         * need to check for it. -- AB, 2010-Jun-04 */
+        if ((widetag_of(start_addr[0]) == CODE_HEADER_WIDETAG)) {
+            lispobj *potential_lra =
+                (lispobj *)(((unsigned long)pointer) - OTHER_POINTER_LOWTAG);
+            if ((widetag_of(potential_lra[0]) == RETURN_PC_HEADER_WIDETAG) &&
+                ((potential_lra - HeaderValue(potential_lra[0])) == start_addr)) {
+                return 1; /* It's as good as we can verify. */
+            }
+        }
+#endif
+
         if ((unsigned long)pointer !=
             ((unsigned long)start_addr+OTHER_POINTER_LOWTAG)) {
             if (gencgc_verbose) {
@@ -2503,6 +2570,8 @@ valid_lisp_pointer_p(lispobj *pointer)
         return 0;
 }
 
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
+
 /* Is there any possibility that pointer is a valid Lisp object
  * reference, and/or something else (e.g. subroutine call return
  * address) which should prevent us from moving the referred-to thing?
@@ -2520,6 +2589,8 @@ possibly_valid_dynamic_space_pointer(lispobj *pointer)
     return looks_like_valid_lisp_pointer_p(pointer, start_addr);
 }
 
+#endif  // defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
+
 /* Adjust large bignum and vector objects. This will adjust the
  * allocated region if the size has shrunk, and move unboxed objects
  * into unboxed pages. The pages are not promoted here, and the
@@ -2738,11 +2809,17 @@ preserve_pointer(void *addr)
      * address referring to something in a CodeObject). This is
      * expensive but important, since it vastly reduces the
      * probability that random garbage will be bogusly interpreted as
-     * a pointer which prevents a page from moving. */
+     * a pointer which prevents a page from moving.
+     *
+     * This only needs to happen on x86oids, where this is used for
+     * conservative roots.  Non-x86oid systems only ever call this
+     * function on known-valid lisp objects. */
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
     if (!(code_page_p(addr_page_index)
           || (is_lisp_pointer((lispobj)addr) &&
               possibly_valid_dynamic_space_pointer(addr))))
         return;
+#endif
 
     /* Find the beginning of the region.  Note that there may be
      * objects in the region preceding the one that we were passed a
@@ -2821,9 +2898,6 @@ preserve_pointer(void *addr)
     /* Check that the page is now static. */
     gc_assert(page_table[addr_page_index].dont_move != 0);
 }
-
-#endif  // defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
-
 \f
 /* If the given page is not write-protected, then scan it for pointers
  * to younger generations or the top temp. generation, if no
@@ -3245,23 +3319,41 @@ static void
 unprotect_oldspace(void)
 {
     page_index_t i;
+    void *region_addr = 0;
+    void *page_addr = 0;
+    unsigned long region_bytes = 0;
 
     for (i = 0; i < last_free_page; i++) {
         if (page_allocated_p(i)
             && (page_table[i].bytes_used != 0)
             && (page_table[i].gen == from_space)) {
-            void *page_start;
-
-            page_start = (void *)page_address(i);
 
             /* Remove any write-protection. We should be able to rely
              * on the write-protect flag to avoid redundant calls. */
             if (page_table[i].write_protected) {
-                os_protect(page_start, PAGE_BYTES, OS_VM_PROT_ALL);
                 page_table[i].write_protected = 0;
+                page_addr = page_address(i);
+                if (!region_addr) {
+                    /* First region. */
+                    region_addr = page_addr;
+                    region_bytes = PAGE_BYTES;
+                } else if (region_addr + region_bytes == page_addr) {
+                    /* Region continue. */
+                    region_bytes += PAGE_BYTES;
+                } else {
+                    /* Unprotect previous region. */
+                    os_protect(region_addr, region_bytes, OS_VM_PROT_ALL);
+                    /* First page in new region. */
+                    region_addr = page_addr;
+                    region_bytes = PAGE_BYTES;
+                }
             }
         }
     }
+    if (region_addr) {
+        /* Unprotect last region. */
+        os_protect(region_addr, region_bytes, OS_VM_PROT_ALL);
+    }
 }
 
 /* Work through all the pages and free any in from_space. This
@@ -3297,17 +3389,8 @@ free_oldspace(void)
                 page_table[last_page].bytes_used;
             page_table[last_page].allocated = FREE_PAGE_FLAG;
             page_table[last_page].bytes_used = 0;
-
-            /* Remove any write-protection. We should be able to rely
-             * on the write-protect flag to avoid redundant calls. */
-            {
-                void  *page_start = (void *)page_address(last_page);
-
-                if (page_table[last_page].write_protected) {
-                    os_protect(page_start, PAGE_BYTES, OS_VM_PROT_ALL);
-                    page_table[last_page].write_protected = 0;
-                }
-            }
+            /* Should already be unprotected by unprotect_oldspace(). */
+            gc_assert(!page_table[last_page].write_protected);
             last_page++;
         }
         while ((last_page < last_free_page)
@@ -3357,6 +3440,23 @@ print_ptr(lispobj *addr)
 }
 #endif
 
+static int
+is_in_stack_space(lispobj ptr)
+{
+    /* For space verification: Pointers can be valid if they point
+     * to a thread stack space.  This would be faster if the thread
+     * structures had page-table entries as if they were part of
+     * the heap space. */
+    struct thread *th;
+    for_each_thread(th) {
+        if ((th->control_stack_start <= (lispobj *)ptr) &&
+            (th->control_stack_end >= (lispobj *)ptr)) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
 static void
 verify_space(lispobj *start, size_t words)
 {
@@ -3384,15 +3484,15 @@ verify_space(lispobj *start, size_t words)
                  * page. XX Could check the offset too. */
                 if (page_allocated_p(page_index)
                     && (page_table[page_index].bytes_used == 0))
-                    lose ("Ptr %x @ %x sees free page.\n", thing, start);
+                    lose ("Ptr %p @ %p sees free page.\n", thing, start);
                 /* Check that it doesn't point to a forwarding pointer! */
                 if (*((lispobj *)native_pointer(thing)) == 0x01) {
-                    lose("Ptr %x @ %x sees forwarding ptr.\n", thing, start);
+                    lose("Ptr %p @ %p sees forwarding ptr.\n", thing, start);
                 }
                 /* Check that its not in the RO space as it would then be a
                  * pointer from the RO to the dynamic space. */
                 if (is_in_readonly_space) {
-                    lose("ptr to dynamic space %x from RO space %x\n",
+                    lose("ptr to dynamic space %p from RO space %x\n",
                          thing, start);
                 }
                 /* Does it point to a plausible object? This check slows
@@ -3406,13 +3506,16 @@ verify_space(lispobj *start, size_t words)
                  * dynamically. */
                 /*
                 if (!possibly_valid_dynamic_space_pointer((lispobj *)thing)) {
-                    lose("ptr %x to invalid object %x\n", thing, start);
+                    lose("ptr %p to invalid object %p\n", thing, start);
                 }
                 */
             } else {
+                extern void funcallable_instance_tramp;
                 /* Verify that it points to another valid space. */
-                if (!to_readonly_space && !to_static_space) {
-                    lose("Ptr %x @ %x sees junk.\n", thing, start);
+                if (!to_readonly_space && !to_static_space
+                    && (thing != (lispobj)&funcallable_instance_tramp)
+                    && !is_in_stack_space(thing)) {
+                    lose("Ptr %p @ %p sees junk.\n", thing, start);
                 }
             }
         } else {
@@ -3489,7 +3592,7 @@ verify_space(lispobj *start, size_t words)
                             /* Only when enabled */
                             && verify_dynamic_code_check) {
                             FSHOW((stderr,
-                                   "/code object at %x in the dynamic space\n",
+                                   "/code object at %p in the dynamic space\n",
                                    start));
                         }
 
@@ -3605,7 +3708,7 @@ verify_space(lispobj *start, size_t words)
                     break;
 
                 default:
-                    lose("Unhandled widetag 0x%x at 0x%x\n",
+                    lose("Unhandled widetag %p at %p\n",
                          widetag_of(*start), start);
                 }
             }
@@ -3780,165 +3883,19 @@ write_protect_generation_pages(generation_index_t generation)
 }
 
 #if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
-
 static void
-scavenge_control_stack()
+scavenge_control_stack(struct thread *th)
 {
-    unsigned long control_stack_size;
-
-    /* This is going to be a big problem when we try to port threads
-     * to PPC... CLH */
-    struct thread *th = arch_os_get_current_thread();
     lispobj *control_stack =
         (lispobj *)(th->control_stack_start);
+    unsigned long control_stack_size =
+        access_control_stack_pointer(th) - control_stack;
 
-    control_stack_size = current_control_stack_pointer - control_stack;
     scavenge(control_stack, control_stack_size);
 }
-
-/* Scavenging Interrupt Contexts */
-
-static int boxed_registers[] = BOXED_REGISTERS;
-
-static void
-scavenge_interrupt_context(os_context_t * context)
-{
-    int i;
-
-#ifdef reg_LIP
-    unsigned long lip;
-    unsigned long lip_offset;
-    int lip_register_pair;
-#endif
-    unsigned long pc_code_offset;
-
-#ifdef ARCH_HAS_LINK_REGISTER
-    unsigned long lr_code_offset;
-#endif
-#ifdef ARCH_HAS_NPC_REGISTER
-    unsigned long npc_code_offset;
-#endif
-
-#ifdef reg_LIP
-    /* Find the LIP's register pair and calculate it's offset */
-    /* before we scavenge the context. */
-
-    /*
-     * I (RLT) think this is trying to find the boxed register that is
-     * closest to the LIP address, without going past it.  Usually, it's
-     * reg_CODE or reg_LRA.  But sometimes, nothing can be found.
-     */
-    lip = *os_context_register_addr(context, reg_LIP);
-    lip_offset = 0x7FFFFFFF;
-    lip_register_pair = -1;
-    for (i = 0; i < (sizeof(boxed_registers) / sizeof(int)); i++) {
-        unsigned long reg;
-        long offset;
-        int index;
-
-        index = boxed_registers[i];
-        reg = *os_context_register_addr(context, index);
-        if ((reg & ~((1L<<N_LOWTAG_BITS)-1)) <= lip) {
-            offset = lip - reg;
-            if (offset < lip_offset) {
-                lip_offset = offset;
-                lip_register_pair = index;
-            }
-        }
-    }
-#endif /* reg_LIP */
-
-    /* Compute the PC's offset from the start of the CODE */
-    /* register. */
-    pc_code_offset = *os_context_pc_addr(context)
-        - *os_context_register_addr(context, reg_CODE);
-#ifdef ARCH_HAS_NPC_REGISTER
-    npc_code_offset = *os_context_npc_addr(context)
-        - *os_context_register_addr(context, reg_CODE);
-#endif /* ARCH_HAS_NPC_REGISTER */
-
-#ifdef ARCH_HAS_LINK_REGISTER
-    lr_code_offset =
-        *os_context_lr_addr(context) -
-        *os_context_register_addr(context, reg_CODE);
-#endif
-
-    /* Scanvenge all boxed registers in the context. */
-    for (i = 0; i < (sizeof(boxed_registers) / sizeof(int)); i++) {
-        int index;
-        lispobj foo;
-
-        index = boxed_registers[i];
-        foo = *os_context_register_addr(context, index);
-        scavenge(&foo, 1);
-        *os_context_register_addr(context, index) = foo;
-
-        scavenge((lispobj*) &(*os_context_register_addr(context, index)), 1);
-    }
-
-#ifdef reg_LIP
-    /* Fix the LIP */
-
-    /*
-     * But what happens if lip_register_pair is -1?
-     * *os_context_register_addr on Solaris (see
-     * solaris_register_address in solaris-os.c) will return
-     * &context->uc_mcontext.gregs[2]. But gregs[2] is REG_nPC. Is
-     * that what we really want? My guess is that that is not what we
-     * want, so if lip_register_pair is -1, we don't touch reg_LIP at
-     * all. But maybe it doesn't really matter if LIP is trashed?
-     */
-    if (lip_register_pair >= 0) {
-        *os_context_register_addr(context, reg_LIP) =
-            *os_context_register_addr(context, lip_register_pair)
-            + lip_offset;
-    }
-#endif /* reg_LIP */
-
-    /* Fix the PC if it was in from space */
-    if (from_space_p(*os_context_pc_addr(context)))
-        *os_context_pc_addr(context) =
-            *os_context_register_addr(context, reg_CODE) + pc_code_offset;
-
-#ifdef ARCH_HAS_LINK_REGISTER
-    /* Fix the LR ditto; important if we're being called from
-     * an assembly routine that expects to return using blr, otherwise
-     * harmless */
-    if (from_space_p(*os_context_lr_addr(context)))
-        *os_context_lr_addr(context) =
-            *os_context_register_addr(context, reg_CODE) + lr_code_offset;
-#endif
-
-#ifdef ARCH_HAS_NPC_REGISTER
-    if (from_space_p(*os_context_npc_addr(context)))
-        *os_context_npc_addr(context) =
-            *os_context_register_addr(context, reg_CODE) + npc_code_offset;
-#endif /* ARCH_HAS_NPC_REGISTER */
-}
-
-void
-scavenge_interrupt_contexts(void)
-{
-    int i, index;
-    os_context_t *context;
-
-    struct thread *th=arch_os_get_current_thread();
-
-    index = fixnum_value(SymbolValue(FREE_INTERRUPT_CONTEXT_INDEX,0));
-
-#if defined(DEBUG_PRINT_CONTEXT_INDEX)
-    printf("Number of active contexts: %d\n", index);
 #endif
 
-    for (i = 0; i < index; i++) {
-        context = th->interrupt_contexts[i];
-        scavenge_interrupt_context(context);
-    }
-}
-
-#endif
-
-#if defined(LISP_FEATURE_SB_THREAD)
+#if defined(LISP_FEATURE_SB_THREAD) && (defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64))
 static void
 preserve_context_registers (os_context_t *c)
 {
@@ -3989,9 +3946,8 @@ garbage_collect_generation(generation_index_t generation, int raise)
     unsigned long bytes_freed;
     page_index_t i;
     unsigned long static_space_size;
-#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
     struct thread *th;
-#endif
+
     gc_assert(generation <= HIGHEST_NORMAL_GENERATION);
 
     /* The oldest generation can't be raised. */
@@ -4091,9 +4047,22 @@ garbage_collect_generation(generation_index_t generation, int raise)
             }
         }
     }
+#else
+    /* Non-x86oid systems don't have "conservative roots" as such, but
+     * the same mechanism is used for objects pinned for use by alien
+     * code. */
+    for_each_thread(th) {
+        lispobj pin_list = SymbolTlValue(PINNED_OBJECTS,th);
+        while (pin_list != NIL) {
+            struct cons *list_entry =
+                (struct cons *)native_pointer(pin_list);
+            preserve_pointer(list_entry->car);
+            pin_list = list_entry->cdr;
+        }
+    }
 #endif
 
-#ifdef QSHOW
+#if QSHOW
     if (gencgc_verbose > 1) {
         long num_dont_move_pages = count_dont_move_pages();
         fprintf(stderr,
@@ -4110,8 +4079,18 @@ garbage_collect_generation(generation_index_t generation, int raise)
      * If not x86, we need to scavenge the interrupt context(s) and the
      * control stack.
      */
-    scavenge_interrupt_contexts();
-    scavenge_control_stack();
+    {
+        struct thread *th;
+        for_each_thread(th) {
+            scavenge_interrupt_contexts(th);
+            scavenge_control_stack(th);
+        }
+
+        /* Scrub the unscavenged control stack space, so that we can't run
+         * into any stale pointers in a later GC (this is done by the
+         * stop-for-gc handler in the other threads). */
+        scrub_control_stack();
+    }
 #endif
 
     /* Scavenge the Lisp functions of the interrupt handlers, taking
@@ -4329,6 +4308,7 @@ collect_garbage(generation_index_t last_gen)
     static page_index_t high_water_mark = 0;
 
     FSHOW((stderr, "/entering collect_garbage(%d)\n", last_gen));
+    log_generation_stats(gc_logfile, "=== GC Start ===");
 
     gc_active_p = 1;
 
@@ -4349,7 +4329,7 @@ collect_garbage(generation_index_t last_gen)
     }
 
     if (gencgc_verbose > 1)
-        print_generation_stats(0);
+        print_generation_stats();
 
     do {
         /* Collect the generation. */
@@ -4360,7 +4340,7 @@ collect_garbage(generation_index_t last_gen)
         } else {
             raise =
                 (gen < last_gen)
-                || (generations[gen].num_gc >= generations[gen].trigger_age);
+                || (generations[gen].num_gc >= generations[gen].number_of_gcs_before_promotion);
         }
 
         if (gencgc_verbose > 1) {
@@ -4387,7 +4367,7 @@ collect_garbage(generation_index_t last_gen)
 
         if (gencgc_verbose > 1) {
             FSHOW((stderr, "GC of generation %d finished:\n", gen));
-            print_generation_stats(0);
+            print_generation_stats();
         }
 
         gen++;
@@ -4397,8 +4377,8 @@ collect_garbage(generation_index_t last_gen)
                      && raise
                      && (generations[gen].bytes_allocated
                          > generations[gen].gc_trigger)
-                     && (gen_av_mem_age(gen)
-                         > generations[gen].min_av_mem_age))));
+                     && (generation_average_age(gen)
+                         > generations[gen].minimum_age_before_gc))));
 
     /* Now if gen-1 was raised all generations before gen are empty.
      * If it wasn't raised then all generations before gen-1 are empty.
@@ -4453,6 +4433,7 @@ collect_garbage(generation_index_t last_gen)
 
     gc_active_p = 0;
 
+    log_generation_stats(gc_logfile, "=== GC End ===");
     SHOW("returning from collect_garbage");
 }
 
@@ -4533,7 +4514,7 @@ gc_free_heap(void)
     }
 
     if (gencgc_verbose > 1)
-        print_generation_stats(0);
+        print_generation_stats();
 
     /* Initialize gc_alloc(). */
     gc_alloc_generation = 0;
@@ -4561,6 +4542,10 @@ gc_init(void)
     page_table_pages = dynamic_space_size/PAGE_BYTES;
     gc_assert(dynamic_space_size == npage_bytes(page_table_pages));
 
+    /* The page_table must be allocated using "calloc" to initialize
+     * the page structures correctly. There used to be a separate
+     * initialization loop (now commented out; see below) but that was
+     * unnecessary and did hurt startup time. */
     page_table = calloc(page_table_pages, sizeof(struct page));
     gc_assert(page_table);
 
@@ -4576,14 +4561,38 @@ gc_init(void)
 
     heap_base = (void*)DYNAMIC_SPACE_START;
 
-    /* Initialize each page structure. */
-    for (i = 0; i < page_table_pages; i++) {
-        /* Initialize all pages as free. */
-        page_table[i].allocated = FREE_PAGE_FLAG;
-        page_table[i].bytes_used = 0;
-
-        /* Pages are not write-protected at startup. */
-        page_table[i].write_protected = 0;
+    /* The page structures are initialized implicitly when page_table
+     * is allocated with "calloc" above. Formerly we had the following
+     * explicit initialization here (comments converted to C99 style
+     * for readability as C's block comments don't nest):
+     *
+     * // Initialize each page structure.
+     * for (i = 0; i < page_table_pages; i++) {
+     *     // Initialize all pages as free.
+     *     page_table[i].allocated = FREE_PAGE_FLAG;
+     *     page_table[i].bytes_used = 0;
+     *
+     *     // Pages are not write-protected at startup.
+     *     page_table[i].write_protected = 0;
+     * }
+     *
+     * Without this loop the image starts up much faster when dynamic
+     * space is large -- which it is on 64-bit platforms already by
+     * default -- and when "calloc" for large arrays is implemented
+     * using copy-on-write of a page of zeroes -- which it is at least
+     * on Linux. In this case the pages that page_table_pages is stored
+     * in are mapped and cleared not before the corresponding part of
+     * dynamic space is used. For example, this saves clearing 16 MB of
+     * memory at startup if the page size is 4 KB and the size of
+     * dynamic space is 4 GB.
+     * FREE_PAGE_FLAG must be 0 for this to work correctly which is
+     * asserted below: */
+    {
+      /* Compile time assertion: If triggered, declares an array
+       * of dimension -1 forcing a syntax error. The intent of the
+       * assignment is to avoid an "unused variable" warning. */
+      char assert_free_page_flag_0[(FREE_PAGE_FLAG) ? -1 : 1];
+      assert_free_page_flag_0[0] = assert_free_page_flag_0[0];
     }
 
     bytes_allocated = 0;
@@ -4602,8 +4611,8 @@ gc_init(void)
         generations[i].cum_sum_bytes_allocated = 0;
         /* the tune-able parameters */
         generations[i].bytes_consed_between_gc = 2000000;
-        generations[i].trigger_age = 1;
-        generations[i].min_av_mem_age = 0.75;
+        generations[i].number_of_gcs_before_promotion = 1;
+        generations[i].minimum_age_before_gc = 0.75;
         generations[i].lutexes = NULL;
     }
 
@@ -4629,18 +4638,24 @@ gencgc_pickup_dynamic(void)
     generation_index_t gen = PSEUDO_STATIC_GENERATION;
     do {
         lispobj *first,*ptr= (lispobj *)page_address(page);
-        page_table[page].allocated = BOXED_PAGE_FLAG;
-        page_table[page].gen = gen;
-        page_table[page].bytes_used = PAGE_BYTES;
-        page_table[page].large_object = 0;
-        page_table[page].write_protected = 0;
-        page_table[page].write_protected_cleared = 0;
-        page_table[page].dont_move = 0;
-        page_table[page].need_to_zero = 1;
+
+        if (!gencgc_partial_pickup || page_allocated_p(page)) {
+          /* It is possible, though rare, for the saved page table
+           * to contain free pages below alloc_ptr. */
+          page_table[page].gen = gen;
+          page_table[page].bytes_used = PAGE_BYTES;
+          page_table[page].large_object = 0;
+          page_table[page].write_protected = 0;
+          page_table[page].write_protected_cleared = 0;
+          page_table[page].dont_move = 0;
+          page_table[page].need_to_zero = 1;
+        }
 
         if (!gencgc_partial_pickup) {
+            page_table[page].allocated = BOXED_PAGE_FLAG;
             first=gc_search_space(prev,(ptr+2)-prev,ptr);
-            if(ptr == first)  prev=ptr;
+            if(ptr == first)
+                prev=ptr;
             page_table[page].region_start_offset =
                 page_address(page) - (void *)prev;
         }
@@ -4720,8 +4735,21 @@ general_alloc_internal(long nbytes, int page_type_flag, struct alloc_region *reg
             /* set things up so that GC happens when we finish the PA
              * section */
             SetSymbolValue(GC_PENDING,T,thread);
-            if (SymbolValue(GC_INHIBIT,thread) == NIL)
-              set_pseudo_atomic_interrupted(thread);
+            if (SymbolValue(GC_INHIBIT,thread) == NIL) {
+                set_pseudo_atomic_interrupted(thread);
+#ifdef LISP_FEATURE_PPC
+                /* PPC calls alloc() from a trap or from pa_alloc(),
+                 * look up the most context if it's from a trap. */
+                {
+                    os_context_t *context =
+                        thread->interrupt_data->allocation_trap_context;
+                    maybe_save_gc_mask_and_block_deferrables
+                        (context ? os_context_sigmask_addr(context) : NULL);
+                }
+#else
+                maybe_save_gc_mask_and_block_deferrables(NULL);
+#endif
+            }
         }
     }
     new_obj = gc_alloc_with_region(nbytes, page_type_flag, region, 0);
@@ -4731,7 +4759,7 @@ general_alloc_internal(long nbytes, int page_type_flag, struct alloc_region *reg
     if ((alloc_signal & FIXNUM_TAG_MASK) == 0) {
         if ((signed long) alloc_signal <= 0) {
             SetSymbolValue(ALLOC_SIGNAL, T, thread);
-            thread_kill(thread->os_thread, SIGPROF);
+            raise(SIGPROF);
         } else {
             SetSymbolValue(ALLOC_SIGNAL,
                            alloc_signal - (1 << N_FIXNUM_TAG_BITS),
@@ -4771,6 +4799,7 @@ general_alloc(long nbytes, int page_type_flag)
 lispobj *
 alloc(long nbytes)
 {
+    gc_assert(get_pseudo_atomic_atomic(arch_os_get_current_thread()));
     return general_alloc(nbytes, BOXED_PAGE_FLAG);
 }
 \f
@@ -4795,7 +4824,7 @@ gencgc_handle_wp_violation(void* fault_addr)
 {
     page_index_t page_index = find_page_index(fault_addr);
 
-#ifdef QSHOW_SIGNALS
+#if QSHOW_SIGNALS
     FSHOW((stderr, "heap WP violation? fault_addr=%x, page_index=%d\n",
            fault_addr, page_index));
 #endif
@@ -4811,6 +4840,9 @@ gencgc_handle_wp_violation(void* fault_addr)
         return 0;
 
     } else {
+        int ret;
+        ret = thread_mutex_lock(&free_pages_lock);
+        gc_assert(ret == 0);
         if (page_table[page_index].write_protected) {
             /* Unprotect the page. */
             os_protect(page_address(page_index), PAGE_BYTES, OS_VM_PROT_ALL);
@@ -4828,6 +4860,8 @@ gencgc_handle_wp_violation(void* fault_addr)
                      page_index, boxed_region.first_page,
                      boxed_region.last_page);
         }
+        ret = thread_mutex_unlock(&free_pages_lock);
+        gc_assert(ret == 0);
         /* Don't worry, we can handle it. */
         return 1;
     }