From: Ondřej Surý <ondrej@isc.org>
Date: Thu, 19 Jan 2023 11:10:28 +0000 (+0100)
Subject: Make the all inuse memory counter atomic operations relaxed
X-Git-Tag: v9.19.10~18^2~4
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=863b2b8bf3feef008db61dd0f6ec43bde81e0c48;p=thirdparty%2Fbind9.git

Make the all inuse memory counter atomic operations relaxed

Instead of enforcing stronger synchronization between threads, make all
the atomic operations relaxed.  We are not really interested in exact
numbers at all times - the single place where we need the exact number
is when the memory context is being destroyed.  Even when there's a
overmem counter, we don't care about exact ordering or exact number.
---

diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 44ad9737da3..07782508e3f 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -361,7 +361,7 @@ mem_realloc(isc_mem_t *ctx, void *old_ptr, size_t old_size, size_t new_size,
  */
 static void
 mem_getstats(isc_mem_t *ctx, size_t size) {
-	atomic_fetch_add_release(&ctx->inuse, size);
+	atomic_fetch_add_relaxed(&ctx->inuse, size);
 }
 
 /*!
@@ -369,7 +369,7 @@ mem_getstats(isc_mem_t *ctx, size_t size) {
  */
 static void
 mem_putstats(isc_mem_t *ctx, size_t size) {
-	atomic_size_t s = atomic_fetch_sub_release(&ctx->inuse, size);
+	atomic_size_t s = atomic_fetch_sub_relaxed(&ctx->inuse, size);
 	INSIST(s >= size);
 }
 
@@ -621,7 +621,7 @@ hi_water(isc_mem_t *ctx) {
 		return (false);
 	}
 
-	inuse = atomic_load_acquire(&ctx->inuse);
+	inuse = atomic_load_relaxed(&ctx->inuse);
 	if (inuse <= hiwater) {
 		return (false);
 	}
@@ -645,7 +645,7 @@ lo_water(isc_mem_t *ctx) {
 		return (false);
 	}
 
-	inuse = atomic_load_acquire(&ctx->inuse);
+	inuse = atomic_load_relaxed(&ctx->inuse);
 	if (inuse >= lowater) {
 		return (false);
 	}
@@ -693,9 +693,9 @@ isc_mem_waterack(isc_mem_t *ctx, int flag) {
 	REQUIRE(VALID_CONTEXT(ctx));
 
 	if (flag == ISC_MEM_LOWATER) {
-		atomic_store(&ctx->hi_called, false);
+		atomic_store_release(&ctx->hi_called, false);
 	} else if (flag == ISC_MEM_HIWATER) {
-		atomic_store(&ctx->hi_called, true);
+		atomic_store_release(&ctx->hi_called, true);
 	}
 }
 
@@ -939,7 +939,7 @@ size_t
 isc_mem_inuse(isc_mem_t *ctx) {
 	REQUIRE(VALID_CONTEXT(ctx));
 
-	return (atomic_load_acquire(&ctx->inuse));
+	return (atomic_load_relaxed(&ctx->inuse));
 }
 
 void
@@ -968,13 +968,13 @@ isc_mem_setwater(isc_mem_t *ctx, isc_mem_water_t water, void *water_arg,
 	if (oldwater == NULL) {
 		REQUIRE(water != NULL && lowater > 0);
 
-		INSIST(atomic_load(&ctx->hi_water) == 0);
-		INSIST(atomic_load(&ctx->lo_water) == 0);
+		INSIST(atomic_load_acquire(&ctx->hi_water) == 0);
+		INSIST(atomic_load_acquire(&ctx->lo_water) == 0);
 
 		ctx->water = water;
 		ctx->water_arg = water_arg;
-		atomic_store(&ctx->hi_water, hiwater);
-		atomic_store(&ctx->lo_water, lowater);
+		atomic_store_release(&ctx->hi_water, hiwater);
+		atomic_store_release(&ctx->lo_water, lowater);
 
 		return;
 	}
@@ -982,8 +982,8 @@ isc_mem_setwater(isc_mem_t *ctx, isc_mem_water_t water, void *water_arg,
 	REQUIRE((water == oldwater && water_arg == oldwater_arg) ||
 		(water == NULL && water_arg == NULL && hiwater == 0));
 
-	atomic_store(&ctx->hi_water, hiwater);
-	atomic_store(&ctx->lo_water, lowater);
+	atomic_store_release(&ctx->hi_water, hiwater);
+	atomic_store_release(&ctx->lo_water, lowater);
 
 	if (atomic_load_acquire(&ctx->hi_called) &&
 	    (atomic_load_acquire(&ctx->inuse) < lowater || lowater == 0U))