From 421b17a622a5037b82aa658dc0cc8264ddd6e711 Mon Sep 17 00:00:00 2001
From: Dmitry Ilvokhin <d@ilvokhin.com>
Date: Wed, 5 Feb 2025 11:00:15 -0800
Subject: [PATCH] Remove age_counter from hpa_central

Before this commit we had two age counters: one global in HPA central
and one local in each HPA shard. We used HPA shard counter, when we are
reused empty pageslab and HPA central counter anywhere else. They
suppose to be comparable, because we use them for allocation placement
decisions, but in reality they are not, there is no ordering guarantees
between them.

At the moment, there is no way for pageslab to migrate between HPA
shards, so we don't actually need HPA central age counter.
---
 include/jemalloc/internal/hpa.h |  2 --
 src/hpa.c                       | 10 +++++-----
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/include/jemalloc/internal/hpa.h b/include/jemalloc/internal/hpa.h
index 1f90a15f..d788d051 100644
--- a/include/jemalloc/internal/hpa.h
+++ b/include/jemalloc/internal/hpa.h
@@ -31,8 +31,6 @@ struct hpa_central_s {
 	size_t eden_len;
 	/* Source for metadata. */
 	base_t *base;
-	/* Number of grow operations done on this hpa_central_t. */
-	uint64_t age_counter;
 
 	/* The HPA hooks. */
 	hpa_hooks_t hooks;
diff --git a/src/hpa.c b/src/hpa.c
index cb3f978c..932cf201 100644
--- a/src/hpa.c
+++ b/src/hpa.c
@@ -82,7 +82,6 @@ hpa_central_init(hpa_central_t *central, base_t *base, const hpa_hooks_t *hooks)
 	central->base = base;
 	central->eden = NULL;
 	central->eden_len = 0;
-	central->age_counter = 0;
 	central->hooks = *hooks;
 	return false;
 }
@@ -95,7 +94,7 @@ hpa_alloc_ps(tsdn_t *tsdn, hpa_central_t *central) {
 
 static hpdata_t *
 hpa_central_extract(tsdn_t *tsdn, hpa_central_t *central, size_t size,
-    bool *oom) {
+    uint64_t age, bool *oom) {
 	/* Don't yet support big allocations; these should get filtered out. */
 	assert(size <= HUGEPAGE);
 	/*
@@ -118,7 +117,7 @@ hpa_central_extract(tsdn_t *tsdn, hpa_central_t *central, size_t size,
 			malloc_mutex_unlock(tsdn, &central->grow_mtx);
 			return NULL;
 		}
-		hpdata_init(ps, central->eden, central->age_counter++);
+		hpdata_init(ps, central->eden, age);
 		central->eden = NULL;
 		central->eden_len = 0;
 		malloc_mutex_unlock(tsdn, &central->grow_mtx);
@@ -168,7 +167,7 @@ hpa_central_extract(tsdn_t *tsdn, hpa_central_t *central, size_t size,
 	assert(central->eden_len % HUGEPAGE == 0);
 	assert(HUGEPAGE_ADDR2BASE(central->eden) == central->eden);
 
-	hpdata_init(ps, central->eden, central->age_counter++);
+	hpdata_init(ps, central->eden, age);
 
 	char *eden_char = (char *)central->eden;
 	eden_char += HUGEPAGE;
@@ -738,7 +737,8 @@ hpa_alloc_batch_psset(tsdn_t *tsdn, hpa_shard_t *shard, size_t size,
 	 * deallocations (and allocations of smaller sizes) may still succeed
 	 * while we're doing this potentially expensive system call.
 	 */
-	hpdata_t *ps = hpa_central_extract(tsdn, shard->central, size, &oom);
+	hpdata_t *ps = hpa_central_extract(tsdn, shard->central, size,
+	    shard->age_counter++, &oom);
 	if (ps == NULL) {
 		malloc_mutex_unlock(tsdn, &shard->grow_mtx);
 		return nsuccess;