Over purge by 1 extent always.

When purging, large allocations are usually the ones that cross the npages_limit
threshold, simply because they are "large".  This means we often leave the large
extent around for a while, which has the downsides of: 1) high RSS and 2) more
chance of them getting fragmented.  Given that they are not likely to be reused
very soon (LRU), let's over purge by 1 extent (which is often large and not
reused frequently).

3 files changed, 5 insertions, 8 deletions

diff --git a/include/jemalloc/internal/extent_externs.h b/include/jemalloc/internal/extent_externs.h
index a76d4e4a..b8a4d026 100644
--- a/include/jemalloc/internal/extent_externs.h
+++ b/include/jemalloc/internal/extent_externs.h
@@ -38,8 +38,7 @@ extent_t *extents_alloc(tsdn_t *tsdn, arena_t *arena,
 void extents_dalloc(tsdn_t *tsdn, arena_t *arena,
     extent_hooks_t **r_extent_hooks, extents_t *extents, extent_t *extent);
 extent_t *extents_evict(tsdn_t *tsdn, arena_t *arena,
-    extent_hooks_t **r_extent_hooks, extents_t *extents, size_t npages_min,
-    size_t npages_max);
+    extent_hooks_t **r_extent_hooks, extents_t *extents, size_t npages_min);
 void extents_prefork(tsdn_t *tsdn, extents_t *extents);
 void extents_postfork_parent(tsdn_t *tsdn, extents_t *extents);
 void extents_postfork_child(tsdn_t *tsdn, extents_t *extents);
diff --git a/src/arena.c b/src/arena.c
index e2462bf7..a28dbfb0 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -912,7 +912,7 @@ arena_stash_decayed(tsdn_t *tsdn, arena_t *arena,
 	extent_t *extent;
 	while (nstashed < npages_decay_max &&
 	    (extent = extents_evict(tsdn, arena, r_extent_hooks, extents,
-	    npages_limit, npages_decay_max - nstashed)) != NULL) {
+	    npages_limit)) != NULL) {
 		extent_list_append(decay_extents, extent);
 		nstashed += extent_size_get(extent) >> LG_PAGE;
 	}
@@ -1226,7 +1226,7 @@ arena_destroy_retained(tsdn_t *tsdn, arena_t *arena) {
 	extent_hooks_t *extent_hooks = extent_hooks_get(arena);
 	extent_t *extent;
 	while ((extent = extents_evict(tsdn, arena, &extent_hooks,
-	    &arena->extents_retained, 0, SIZE_MAX)) != NULL) {
+	    &arena->extents_retained, 0)) != NULL) {
 		extent_destroy_wrapper(tsdn, arena, &extent_hooks, extent);
 	}
 }
diff --git a/src/extent.c b/src/extent.c
index c531da24..bca703fc 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -481,7 +481,7 @@ extents_dalloc(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
 
 extent_t *
 extents_evict(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
-    extents_t *extents, size_t npages_min, size_t npages_max) {
+    extents_t *extents, size_t npages_min) {
 	rtree_ctx_t rtree_ctx_fallback;
 	rtree_ctx_t *rtree_ctx = tsdn_rtree_ctx(tsdn, &rtree_ctx_fallback);
 
@@ -499,11 +499,9 @@ extents_evict(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
 			goto label_return;
 		}
 		/* Check the eviction limit. */
-		size_t npages = extent_size_get(extent) >> LG_PAGE;
 		size_t extents_npages = atomic_load_zu(&extents->npages,
 		    ATOMIC_RELAXED);
-		if (extents_npages - npages < npages_min ||
-		    npages > npages_max) {
+		if (extents_npages <= npages_min) {
 			extent = NULL;
 			goto label_return;
 		}