[PATCH] drop heap page support for Ruby <= 3.0

[Eric Wong <e@80x24.org>]

Ruby 3.1 uses mmap, nowadays, and I don't think it's worth the
effort to suport it since mmap and munmap don't require the
symmetry *memalign + free do.
---
 Keeping this separate from the upcoming mwrap-perl merge which
 features major changes including more common code.

 ext/mwrap/extconf.rb |   7 -
 ext/mwrap/mwrap.c    | 327 ++-----------------------------------------
 lib/mwrap_rack.rb    |  51 -------
 test/test_mwrap.rb   |  38 -----
 4 files changed, 12 insertions(+), 411 deletions(-)

diff --git a/ext/mwrap/extconf.rb b/ext/mwrap/extconf.rb
index 1828407..e8d3cc6 100644
--- a/ext/mwrap/extconf.rb
+++ b/ext/mwrap/extconf.rb
@@ -25,11 +25,4 @@ else
   abort 'missing __builtin_add_overflow'
 end
 
-begin
-  if n = GC::INTERNAL_CONSTANTS[:HEAP_PAGE_SIZE]
-    $defs << "-DHEAP_PAGE_SIZE=#{n}"
-  end
-rescue NameError
-end
-
 create_makefile 'mwrap'
diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
index 08761d6..6875486 100644
--- a/ext/mwrap/mwrap.c
+++ b/ext/mwrap/mwrap.c
@@ -51,19 +51,6 @@ static size_t total_bytes_inc, total_bytes_dec;
 /* true for glibc/dlmalloc/ptmalloc, not sure about jemalloc */
 #define ASSUMED_MALLOC_ALIGNMENT (sizeof(void *) * 2)
 
-/* match values in Ruby gc.c */
-#define HEAP_PAGE_ALIGN_LOG 14
-enum {
-	HEAP_PAGE_ALIGN = (1UL << HEAP_PAGE_ALIGN_LOG)
-#ifndef HEAP_PAGE_SIZE /* Ruby 2.6-2.7 only */
-	,
-	REQUIRED_SIZE_BY_MALLOC = (sizeof(size_t) * 5),
-	HEAP_PAGE_SIZE = (HEAP_PAGE_ALIGN - REQUIRED_SIZE_BY_MALLOC)
-#endif
-};
-
-#define IS_HEAP_PAGE_BODY ((struct src_loc *)-1)
-
 #ifdef __FreeBSD__
 void *__malloc(size_t);
 void __free(void *);
@@ -111,33 +98,6 @@ static union padded_mutex mutexes[MUTEX_NR] = {
 #endif
 };
 
-#define ACC_INIT(name) { .nr=0, .min=INT64_MAX, .max=-1, .m2=0, .mean=0 }
-struct acc {
-	uint64_t nr;
-	int64_t min;
-	int64_t max;
-	double m2;
-	double mean;
-};
-
-/* for tracking 16K-aligned heap page bodies (protected by GVL) */
-struct {
-	pthread_mutex_t lock;
-	struct cds_list_head bodies;
-	struct cds_list_head freed;
-
-	struct acc alive;
-	struct acc reborn;
-} hpb_stats = {
-#if STATIC_MTX_INIT_OK
-	.lock = PTHREAD_MUTEX_INITIALIZER,
-#endif
-	.bodies = CDS_LIST_HEAD_INIT(hpb_stats.bodies),
-	.freed = CDS_LIST_HEAD_INIT(hpb_stats.freed),
-	.alive = ACC_INIT(hpb_stats.alive),
-	.reborn = ACC_INIT(hpb_stats.reborn)
-};
-
 static pthread_mutex_t *mutex_assign(void)
 {
 	return &mutexes[uatomic_add_return(&mutex_i, 1) & MUTEX_MASK].mtx;
@@ -168,11 +128,6 @@ __attribute__((constructor)) static void resolve_malloc(void)
 				_exit(1);
 			}
 		}
-		err = pthread_mutex_init(&hpb_stats.lock, 0);
-		if (err) {
-			fprintf(stderr, "error: %s\n", strerror(err));
-			_exit(1);
-		}
 		/* initialize mutexes used by urcu-bp */
 		rcu_read_lock();
 		rcu_read_unlock();
@@ -300,9 +255,6 @@ struct alloc_hdr {
 			struct src_loc *loc;
 		} live;
 		struct rcu_head dead;
-		struct {
-			size_t at; /* rb_gc_count() */
-		} hpb_freed;
 	} as;
 	void *real; /* what to call real_free on */
 	size_t size;
@@ -344,64 +296,6 @@ static int loc_eq(struct cds_lfht_node *node, const void *key)
 		memcmp(k->k, existing->k, loc_size(k)) == 0);
 }
 
-/* note: not atomic */
-static void
-acc_add(struct acc *acc, size_t val)
-{
-	double delta = val - acc->mean;
-	uint64_t nr = ++acc->nr;
-
-	/* just don't divide-by-zero if we ever hit this (unlikely :P) */
-	if (nr)
-		acc->mean += delta / nr;
-
-	acc->m2 += delta * (val - acc->mean);
-	if ((int64_t)val < acc->min)
-		acc->min = (int64_t)val;
-	if ((int64_t)val > acc->max)
-		acc->max = (int64_t)val;
-}
-
-#if SIZEOF_LONG == 8
-# define INT64toNUM(x) LONG2NUM((long)x)
-#elif defined(HAVE_LONG_LONG) && SIZEOF_LONG_LONG == 8
-# define INT64toNUM(x) LL2NUM((LONG_LONG)x)
-#endif
-
-static VALUE
-acc_max(const struct acc *acc)
-{
-	return INT64toNUM(acc->max);
-}
-
-static VALUE
-acc_min(const struct acc *acc)
-{
-	return acc->min == INT64_MAX ? INT2FIX(-1) : INT64toNUM(acc->min);
-}
-
-static VALUE
-acc_mean(const struct acc *acc)
-{
-	return DBL2NUM(acc->nr ? acc->mean : HUGE_VAL);
-}
-
-static double
-acc_stddev_dbl(const struct acc *acc)
-{
-	if (acc->nr > 1) {
-		double variance = acc->m2 / (acc->nr - 1);
-		return sqrt(variance);
-	}
-	return 0.0;
-}
-
-static VALUE
-acc_stddev(const struct acc *acc)
-{
-	return DBL2NUM(acc_stddev_dbl(acc));
-}
-
 static struct src_loc *totals_add_rcu(const struct src_loc *k)
 {
 	struct cds_lfht_iter iter;
@@ -519,7 +413,7 @@ void free(void *p)
 		struct src_loc *l = h->as.live.loc;
 
 		if (!real_free) return; /* oh well, leak a little */
-		if (l && l != IS_HEAP_PAGE_BODY) {
+		if (l) {
 			size_t age = generation - h->as.live.gen;
 
 			uatomic_add(&total_bytes_dec, h->size);
@@ -534,19 +428,6 @@ void free(void *p)
 			mutex_unlock(l->mtx);
 
 			call_rcu(&h->as.dead, free_hdr_rcu);
-		} else if (l == IS_HEAP_PAGE_BODY) {
-			size_t gen = generation;
-			size_t age = gen - h->as.live.gen;
-
-			h->as.hpb_freed.at = gen;
-
-			mutex_lock(&hpb_stats.lock);
-			acc_add(&hpb_stats.alive, age);
-
-			/* hpb_stats.bodies => hpb_stats.freed */
-			cds_list_move(&h->anode, &hpb_stats.freed);
-
-			mutex_unlock(&hpb_stats.lock);
 		} else {
 			real_free(h->real);
 		}
@@ -614,65 +495,18 @@ internal_memalign(void **pp, size_t alignment, size_t size, uintptr_t caller)
 		return ENOMEM;
 
 
-	if (alignment == HEAP_PAGE_ALIGN && size == HEAP_PAGE_SIZE) {
-		if (has_ec_p()) generation = rb_gc_count();
-		l = IS_HEAP_PAGE_BODY;
-	} else {
-		l = update_stats_rcu_lock(size, caller);
-	}
+	l = update_stats_rcu_lock(size, caller);
 
-	if (l == IS_HEAP_PAGE_BODY) {
-		void *p;
-		size_t gen = generation;
-
-		mutex_lock(&hpb_stats.lock);
-
-		/* reuse existing entry */
-		if (!cds_list_empty(&hpb_stats.freed)) {
-			size_t deathspan;
-
-			h = cds_list_first_entry(&hpb_stats.freed,
-						 struct alloc_hdr, anode);
-			/* hpb_stats.freed => hpb_stats.bodies */
-			cds_list_move(&h->anode, &hpb_stats.bodies);
-			assert(h->size == size);
-			assert(h->real);
-			real = h->real;
-			p = hdr2ptr(h);
-			assert(ptr_is_aligned(p, alignment));
-
-			deathspan = gen - h->as.hpb_freed.at;
-			acc_add(&hpb_stats.reborn, deathspan);
-		}
-		else {
-			real = real_malloc(asize);
-			if (!real) return ENOMEM;
-
-			p = hdr2ptr(real);
-			if (!ptr_is_aligned(p, alignment))
-				p = ptr_align(p, alignment);
-			h = ptr2hdr(p);
-			h->size = size;
-			h->real = real;
-			cds_list_add(&h->anode, &hpb_stats.bodies);
-		}
-		mutex_unlock(&hpb_stats.lock);
-		h->as.live.loc = l;
-		h->as.live.gen = gen;
+	real = real_malloc(asize);
+	if (real) {
+		void *p = hdr2ptr(real);
+		if (!ptr_is_aligned(p, alignment))
+			p = ptr_align(p, alignment);
+		h = ptr2hdr(p);
+		alloc_insert_rcu(l, h, size, real);
 		*pp = p;
 	}
-	else {
-		real = real_malloc(asize);
-		if (real) {
-			void *p = hdr2ptr(real);
-			if (!ptr_is_aligned(p, alignment))
-				p = ptr_align(p, alignment);
-			h = ptr2hdr(p);
-			alloc_insert_rcu(l, h, size, real);
-			*pp = p;
-		}
-		update_stats_rcu_unlock(l);
-	}
+	update_stats_rcu_unlock(l);
 
 	return real ? 0 : ENOMEM;
 }
@@ -1243,73 +1077,6 @@ static VALUE total_dec(VALUE mod)
 	return SIZET2NUM(total_bytes_dec);
 }
 
-static VALUE hpb_each_yield(VALUE ignore)
-{
-	struct alloc_hdr *h, *next;
-
-	cds_list_for_each_entry_safe(h, next, &hpb_stats.bodies, anode) {
-		VALUE v[2]; /* [ generation, address ] */
-		void *addr = hdr2ptr(h);
-		assert(ptr_is_aligned(addr, HEAP_PAGE_ALIGN));
-		v[0] = LONG2NUM((long)addr);
-		v[1] = SIZET2NUM(h->as.live.gen);
-		rb_yield_values2(2, v);
-	}
-	return Qnil;
-}
-
-/*
- * call-seq:
- *
- *     Mwrap::HeapPageBody.each { |gen, addr| } -> Integer
- *
- * Yields the generation (GC.count) the heap page body was created
- * and address of the heap page body as an Integer.  Returns the
- * number of allocated pages as an Integer.  This return value should
- * match the result of GC.stat(:heap_allocated_pages)
- */
-static VALUE hpb_each(VALUE mod)
-{
-	++locating;
-	return rb_ensure(hpb_each_yield, Qfalse, reset_locating, 0);
-}
-
-/*
- * call-seq:
- *
- *	Mwrap::HeapPageBody.stat -> Hash
- *	Mwrap::HeapPageBody.stat(hash) -> hash
- *
- * The maximum lifespan of a heap page body in the Ruby VM.
- * This may be Infinity if no heap page bodies were ever freed.
- */
-static VALUE hpb_stat(int argc, VALUE *argv, VALUE hpb)
-{
-	VALUE h;
-
-	rb_scan_args(argc, argv, "01", &h);
-	if (NIL_P(h))
-		h = rb_hash_new();
-	else if (!RB_TYPE_P(h, T_HASH))
-		rb_raise(rb_eTypeError, "not a hash %+"PRIsVALUE, h);
-
-	++locating;
-#define S(x) ID2SYM(rb_intern(#x))
-	rb_hash_aset(h, S(lifespan_max), acc_max(&hpb_stats.alive));
-	rb_hash_aset(h, S(lifespan_min), acc_min(&hpb_stats.alive));
-	rb_hash_aset(h, S(lifespan_mean), acc_mean(&hpb_stats.alive));
-	rb_hash_aset(h, S(lifespan_stddev), acc_stddev(&hpb_stats.alive));
-	rb_hash_aset(h, S(deathspan_max), acc_max(&hpb_stats.reborn));
-	rb_hash_aset(h, S(deathspan_min), acc_min(&hpb_stats.reborn));
-	rb_hash_aset(h, S(deathspan_mean), acc_mean(&hpb_stats.reborn));
-	rb_hash_aset(h, S(deathspan_stddev), acc_stddev(&hpb_stats.reborn));
-	rb_hash_aset(h, S(resurrects), SIZET2NUM(hpb_stats.reborn.nr));
-#undef S
-	--locating;
-
-	return h;
-}
-
 /*
  * Document-module: Mwrap
  *
@@ -1328,19 +1095,13 @@ static VALUE hpb_stat(int argc, VALUE *argv, VALUE hpb)
  * * dump_fd: a writable FD to dump to
  * * dump_path: a path to dump to, the file is opened in O_APPEND mode
  * * dump_min: the minimum allocation size (total) to dump
- * * dump_heap: mask of heap_page_body statistics to dump
  *
  * If both `dump_fd' and `dump_path' are specified, dump_path takes
  * precedence.
- *
- * dump_heap bitmask
- * * 0x01 - summary stats (same info as HeapPageBody.stat)
- * * 0x02 - all live heaps (similar to HeapPageBody.each)
- * * 0x04 - skip non-heap_page_body-related output
  */
 void Init_mwrap(void)
 {
-	VALUE mod, hpb;
+	VALUE mod;
 
 	++locating;
 	mod = rb_define_module("Mwrap");
@@ -1372,67 +1133,9 @@ void Init_mwrap(void)
 	rb_define_method(cSrcLoc, "max_lifespan", src_loc_max_lifespan, 0);
 	rb_define_method(cSrcLoc, "name", src_loc_name, 0);
 
-	/*
-	 * Information about "struct heap_page_body" allocations from
-	 * Ruby gc.c.  This can be useful for tracking fragmentation
-	 * from posix_memalign(3) use in mainline Ruby:
-	 *
-	 *   https://sourceware.org/bugzilla/show_bug.cgi?id=14581
-	 *
-	 * These statistics are never reset by Mwrap.reset or
-	 * any other method.  They only make sense in the context
-	 * of an entire program lifetime.
-	 */
-	hpb = rb_define_class_under(mod, "HeapPageBody", rb_cObject);
-	rb_define_singleton_method(hpb, "stat", hpb_stat, -1);
-	rb_define_singleton_method(hpb, "each", hpb_each, 0);
-
 	--locating;
 }
 
-enum {
-	DUMP_HPB_STATS = 0x1,
-	DUMP_HPB_EACH = 0x2,
-	DUMP_HPB_EXCL = 0x4,
-};
-
-static void dump_hpb(FILE *fp, unsigned flags)
-{
-	if (flags & DUMP_HPB_STATS) {
-		fprintf(fp,
-			"lifespan_max: %"PRId64"\n"
-			"lifespan_min:%s%"PRId64"\n"
-			"lifespan_mean: %0.3f\n"
-			"lifespan_stddev: %0.3f\n"
-			"deathspan_max: %"PRId64"\n"
-			"deathspan_min:%s%"PRId64"\n"
-			"deathspan_mean: %0.3f\n"
-			"deathspan_stddev: %0.3f\n"
-			"gc_count: %zu\n",
-			hpb_stats.alive.max,
-			hpb_stats.alive.min == INT64_MAX ? " -" : " ",
-			hpb_stats.alive.min,
-			hpb_stats.alive.mean,
-			acc_stddev_dbl(&hpb_stats.alive),
-			hpb_stats.reborn.max,
-			hpb_stats.reborn.min == INT64_MAX ? " -" : " ",
-			hpb_stats.reborn.min,
-			hpb_stats.reborn.mean,
-			acc_stddev_dbl(&hpb_stats.reborn),
-			/* n.b.: unsafe to call rb_gc_count() in destructor */
-			generation);
-	}
-	if (flags & DUMP_HPB_EACH) {
-		struct alloc_hdr *h;
-
-		cds_list_for_each_entry(h, &hpb_stats.bodies, anode) {
-			void *addr = hdr2ptr(h);
-
-			fprintf(fp, "%p\t%zu\n", addr, h->as.live.gen);
-		}
-	}
-}
-
 /* rb_cloexec_open isn't usable by non-Ruby processes */
 #ifndef O_CLOEXEC
 #  define O_CLOEXEC 0
@@ -1446,7 +1149,6 @@ static void mwrap_dump_destructor(void)
 	struct dump_arg a = { .min = 0 };
 	size_t i;
 	int dump_fd;
-	unsigned dump_heap = 0;
 	char *dump_path;
 	char *s;
 
@@ -1478,9 +1180,6 @@ static void mwrap_dump_destructor(void)
 	if ((s = strstr(opt, "dump_min:")))
 		sscanf(s, "dump_min:%zu", &a.min);
 
-	if ((s = strstr(opt, "dump_heap:")))
-		sscanf(s, "dump_heap:%u", &dump_heap);
-
 	switch (dump_fd) {
 	case 0: goto out;
 	case 1: a.fp = stdout; break;
@@ -1500,9 +1199,7 @@ static void mwrap_dump_destructor(void)
 		}
 		/* we'll leak some memory here, but this is a destructor */
 	}
-	if ((dump_heap & DUMP_HPB_EXCL) == 0)
-		dump_to_file(&a);
-	dump_hpb(a.fp, dump_heap);
+	dump_to_file(&a);
 out:
 	--locating;
 }
diff --git a/lib/mwrap_rack.rb b/lib/mwrap_rack.rb
index 53380b9..c777a78 100644
--- a/lib/mwrap_rack.rb
+++ b/lib/mwrap_rack.rb
@@ -89,54 +89,6 @@ class MwrapRack
     end
   end
 
-  class HeapPages # :nodoc:
-    include HtmlResponse
-    HEADER = '<tr><th>address</th><th>generation</th></tr>'
-
-    def hpb_rows
-      Mwrap::HeapPageBody.stat(stat = Thread.current[:mwrap_hpb_stat] ||= {})
-      %i(lifespan_max lifespan_min lifespan_mean lifespan_stddev
-         deathspan_max deathspan_min deathspan_mean deathspan_stddev
-         resurrects
-        ).map! do |k|
-         "<tr><td>#{k}</td><td>#{stat[k]}</td></tr>\n"
-      end.join
-    end
-
-    def gc_stat_rows
-      GC.stat(stat = Thread.current[:mwrap_gc_stat] ||= {})
-      %i(count heap_allocated_pages heap_eden_pages heap_tomb_pages
-          total_allocated_pages total_freed_pages).map do |k|
-         "<tr><td>GC.stat(:#{k})</td><td>#{stat[k]}</td></tr>\n"
-      end.join
-    end
-
-    GC_STAT_URL = 'https://docs.ruby-lang.org/en/trunk/GC.html#method-c-stat'
-    GC_STAT_HELP = <<~EOM
-      <p>Non-Infinity lifespans can indicate fragmentation.
-      <p>See <a
-      href="#{GC_STAT_URL}">#{GC_STAT_URL}</a> for info on GC.stat values.
-    EOM
-
-    def each
-      Mwrap.quiet do
-        yield("<html><head><title>heap pages</title></head>" \
-              "<body><h1>heap pages</h1>" \
-              "<table><tr><th>stat</th><th>value</th></tr>\n" \
-              "#{hpb_rows}" \
-              "#{gc_stat_rows}" \
-              "</table>\n" \
-              "#{GC_STAT_HELP}" \
-              "<table>#{HEADER}")
-        Mwrap::HeapPageBody.each do |addr, generation|
-          addr = -sprintf('0x%x', addr)
-          yield(-"<tr><td>#{addr}</td><td>#{generation}</td></tr>\n")
-        end
-        yield "</table></body></html>\n"
-      end
-    end
-  end
-
   def r404 # :nodoc:
     [404,{'Content-Type'=>'text/plain'},["Not found\n"]]
   end
@@ -152,15 +104,12 @@ class MwrapRack
       loc = -CGI.unescape($1)
       loc = Mwrap[loc] or return r404
       EachAt.new(loc).response
-    when '/heap_pages'
-      HeapPages.new.response
     when '/'
       n = 2000
       u = 'https://80x24.org/mwrap/README.html'
       b = -('<html><head><title>Mwrap demo</title></head>' \
           "<body><p><a href=\"each/#{n}\">allocations &gt;#{n} bytes</a>" \
           "<p><a href=\"#{u}\">#{u}</a>" \
-          "<p><a href=\"heap_pages\">heap pages</a>" \
           "</body></html>\n")
       [ 200, {'Content-Type'=>'text/html','Content-Length'=>-b.size.to_s},[b]]
     else
diff --git a/test/test_mwrap.rb b/test/test_mwrap.rb
index eaa65cb..6522167 100644
--- a/test/test_mwrap.rb
+++ b/test/test_mwrap.rb
@@ -59,13 +59,6 @@ class TestMwrap < Test::Unit::TestCase
       res = system(env, *cmd)
       assert res, $?.inspect
       assert_match(/\b1\d{4}\s+[1-9]\d*\s+-e:1$/, tmp.read)
-
-      tmp.rewind
-      tmp.truncate(0)
-      env['MWRAP'] = "dump_path:#{tmp.path},dump_heap:5"
-      res = system(env, *cmd)
-      assert res, $?.inspect
-      assert_match %r{lifespan_stddev}, tmp.read
     end
   end
 
@@ -295,35 +288,4 @@ class TestMwrap < Test::Unit::TestCase
         abort 'freed more than allocated'
     end;
   end
-
-  def test_heap_page_body
-    assert_separately(+"#{<<~"begin;"}\n#{<<~'end;'}")
-    begin;
-      require 'mwrap'
-      require 'rubygems' # use up some memory
-      ap = GC.stat(:heap_allocated_pages)
-      h = {}
-      nr = 0
-      Mwrap::HeapPageBody.each do |addr, gen|
-        nr += 1
-        gen <= GC.count && gen >= 0 or abort "bad generation: #{gen}"
-        (0 == (addr & 16383)) or abort "addr not aligned: #{'%x' % addr}"
-      end
-      if RUBY_VERSION.to_f < 3.1 # 3.1+ uses mmap on platforms we care about
-        nr == ap or abort "HeapPageBody.each missed page #{nr} != #{ap}"
-      end
-      10.times { (1..20000).to_a.map(&:to_s) }
-      3.times { GC.start }
-      Mwrap::HeapPageBody.stat(h)
-      Integer === h[:lifespan_max] or abort 'lifespan_max not recorded'
-      Integer === h[:lifespan_min] or abort 'lifespan_min not recorded'
-      Float === h[:lifespan_mean] or abort 'lifespan_mean not recorded'
-      3.times { GC.start }
-      10.times { (1..20000).to_a.map(&:to_s) }
-      Mwrap::HeapPageBody.stat(h)
-      h[:deathspan_min] <= h[:deathspan_max] or
-        abort 'wrong min/max deathtime'
-      Float === h[:deathspan_mean] or abort 'deathspan_mean not recorded'
-    end;
-  end
 end