Implement dynamic per arena control over dirty page purging.

Add mallctls:
- arenas.lg_dirty_mult is initialized via opt.lg_dirty_mult, and can be
  modified to change the initial lg_dirty_mult setting for newly created
  arenas.
- arena.<i>.lg_dirty_mult controls an individual arena's dirty page
  purging threshold, and synchronously triggers any purging that may be
  necessary to maintain the constraint.
- arena.<i>.chunk.purge allows the per arena dirty page purging function
  to be replaced.

This resolves #93.

2 files changed, 71 insertions, 5 deletions

diff --git a/test/unit/mallctl.c b/test/unit/mallctl.c
index 5960496..31ada19 100644
--- a/test/unit/mallctl.c
+++ b/test/unit/mallctl.c
@@ -348,6 +348,38 @@ TEST_BEGIN(test_thread_arena)
 }
 TEST_END
 
+TEST_BEGIN(test_arena_i_lg_dirty_mult)
+{
+	ssize_t lg_dirty_mult, orig_lg_dirty_mult, prev_lg_dirty_mult;
+	size_t sz = sizeof(ssize_t);
+
+	assert_d_eq(mallctl("arena.0.lg_dirty_mult", &orig_lg_dirty_mult, &sz,
+	    NULL, 0), 0, "Unexpected mallctl() failure");
+
+	lg_dirty_mult = -2;
+	assert_d_eq(mallctl("arena.0.lg_dirty_mult", NULL, NULL,
+	    &lg_dirty_mult, sizeof(ssize_t)), EFAULT,
+	    "Unexpected mallctl() success");
+
+	lg_dirty_mult = (sizeof(size_t) << 3);
+	assert_d_eq(mallctl("arena.0.lg_dirty_mult", NULL, NULL,
+	    &lg_dirty_mult, sizeof(ssize_t)), EFAULT,
+	    "Unexpected mallctl() success");
+
+	for (prev_lg_dirty_mult = orig_lg_dirty_mult, lg_dirty_mult = -1;
+	    lg_dirty_mult < (sizeof(ssize_t) << 3); prev_lg_dirty_mult =
+	    lg_dirty_mult, lg_dirty_mult++) {
+		ssize_t old_lg_dirty_mult;
+
+		assert_d_eq(mallctl("arena.0.lg_dirty_mult", &old_lg_dirty_mult,
+		    &sz, &lg_dirty_mult, sizeof(ssize_t)), 0,
+		    "Unexpected mallctl() failure");
+		assert_zd_eq(old_lg_dirty_mult, prev_lg_dirty_mult,
+		    "Unexpected old arena.0.lg_dirty_mult");
+	}
+}
+TEST_END
+
 TEST_BEGIN(test_arena_i_purge)
 {
 	unsigned narenas;
@@ -427,6 +459,38 @@ TEST_BEGIN(test_arenas_initialized)
 }
 TEST_END
 
+TEST_BEGIN(test_arenas_lg_dirty_mult)
+{
+	ssize_t lg_dirty_mult, orig_lg_dirty_mult, prev_lg_dirty_mult;
+	size_t sz = sizeof(ssize_t);
+
+	assert_d_eq(mallctl("arenas.lg_dirty_mult", &orig_lg_dirty_mult, &sz,
+	    NULL, 0), 0, "Unexpected mallctl() failure");
+
+	lg_dirty_mult = -2;
+	assert_d_eq(mallctl("arenas.lg_dirty_mult", NULL, NULL,
+	    &lg_dirty_mult, sizeof(ssize_t)), EFAULT,
+	    "Unexpected mallctl() success");
+
+	lg_dirty_mult = (sizeof(size_t) << 3);
+	assert_d_eq(mallctl("arenas.lg_dirty_mult", NULL, NULL,
+	    &lg_dirty_mult, sizeof(ssize_t)), EFAULT,
+	    "Unexpected mallctl() success");
+
+	for (prev_lg_dirty_mult = orig_lg_dirty_mult, lg_dirty_mult = -1;
+	    lg_dirty_mult < (sizeof(ssize_t) << 3); prev_lg_dirty_mult =
+	    lg_dirty_mult, lg_dirty_mult++) {
+		ssize_t old_lg_dirty_mult;
+
+		assert_d_eq(mallctl("arenas.lg_dirty_mult", &old_lg_dirty_mult,
+		    &sz, &lg_dirty_mult, sizeof(ssize_t)), 0,
+		    "Unexpected mallctl() failure");
+		assert_zd_eq(old_lg_dirty_mult, prev_lg_dirty_mult,
+		    "Unexpected old arenas.lg_dirty_mult");
+	}
+}
+TEST_END
+
 TEST_BEGIN(test_arenas_constants)
 {
 
@@ -554,9 +618,11 @@ main(void)
 	    test_tcache_none,
 	    test_tcache,
 	    test_thread_arena,
+	    test_arena_i_lg_dirty_mult,
 	    test_arena_i_purge,
 	    test_arena_i_dss,
 	    test_arenas_initialized,
+	    test_arenas_lg_dirty_mult,
 	    test_arenas_constants,
 	    test_arenas_bin_constants,
 	    test_arenas_lrun_constants,
diff --git a/test/unit/rtree.c b/test/unit/rtree.c
index 556c4a8..496e03a 100644
--- a/test/unit/rtree.c
+++ b/test/unit/rtree.c
@@ -22,7 +22,7 @@ TEST_BEGIN(test_rtree_get_empty)
 		rtree_t rtree;
 		assert_false(rtree_new(&rtree, i, node_alloc, node_dalloc),
 		    "Unexpected rtree_new() failure");
-		assert_ptr_eq(rtree_get(&rtree, 0), NULL,
+		assert_ptr_null(rtree_get(&rtree, 0),
 		    "rtree_get() should return NULL for empty tree");
 		rtree_delete(&rtree);
 	}
@@ -75,8 +75,8 @@ TEST_BEGIN(test_rtree_bits)
 				    "get key=%#"PRIxPTR, i, j, k, keys[j],
 				    keys[k]);
 			}
-			assert_ptr_eq(rtree_get(&rtree,
-			    (((uintptr_t)1) << (sizeof(uintptr_t)*8-i))), NULL,
+			assert_ptr_null(rtree_get(&rtree,
+			    (((uintptr_t)1) << (sizeof(uintptr_t)*8-i))),
 			    "Only leftmost rtree leaf should be set; "
 			    "i=%u, j=%u", i, j);
 			rtree_set(&rtree, keys[j], NULL);
@@ -117,11 +117,11 @@ TEST_BEGIN(test_rtree_random)
 
 		for (j = 0; j < NSET; j++) {
 			rtree_set(&rtree, keys[j], NULL);
-			assert_ptr_eq(rtree_get(&rtree, keys[j]), NULL,
+			assert_ptr_null(rtree_get(&rtree, keys[j]),
 			    "rtree_get() should return previously set value");
 		}
 		for (j = 0; j < NSET; j++) {
-			assert_ptr_eq(rtree_get(&rtree, keys[j]), NULL,
+			assert_ptr_null(rtree_get(&rtree, keys[j]),
 			    "rtree_get() should return previously set value");
 		}