From 46690c9ec036cede074476caa05ecd6fe954bd23 Mon Sep 17 00:00:00 2001
From: Dmitry Ilvokhin <d@ilvokhin.com>
Date: Thu, 28 Nov 2024 07:10:33 -0800
Subject: [PATCH] Fix `test_retained` on boxes with a lot of CPUs

We are trying to create `ncpus * 2` threads for this test and place them
into `VARIABLE_ARRAY`, but `VARIABLE_ARRAY` can not be more than
`VARIABLE_ARRAY_SIZE_MAX` bytes. When there are a lot of threads on the
box test always fails.

```
$ nproc
176

$ make -j`nproc` tests_unit && ./test/unit/retained
<jemalloc>: ../test/unit/retained.c:123: Failed assertion:
"sizeof(thd_t) * (nthreads) <= VARIABLE_ARRAY_SIZE_MAX"
Aborted (core dumped)
```

There is no need for high concurrency for this test as we are only
checking stats there and it's behaviour is quite stable regarding number
of allocating threads.

Limited number of threads to 16 to save compute resources (on CI for
example) and reduce tests running time.

Before the change (`nproc` is 80 on this box).

```
$ make -j`nproc` tests_unit && time ./test/unit/retained
<...>
real    0m0.372s
user    0m14.236s
sys     0m12.338s
```

After the change (same box).

```
$ make -j`nproc` tests_unit && time ./test/unit/retained
<...>
real    0m0.018s
user    0m0.108s
sys     0m0.068s
```
---
 test/unit/retained.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/test/unit/retained.c b/test/unit/retained.c
index 340f2d38..40cbb0cd 100644
--- a/test/unit/retained.c
+++ b/test/unit/retained.c
@@ -110,8 +110,15 @@ TEST_BEGIN(test_retained) {
 	atomic_store_u(&epoch, 0, ATOMIC_RELAXED);
 
 	unsigned nthreads = ncpus * 2;
-	if (LG_SIZEOF_PTR < 3 && nthreads > 16) {
-		nthreads = 16; /* 32-bit platform could run out of vaddr. */
+	if (nthreads > 16) {
+		/*
+		 * Limit number of threads we are creating for following
+		 * reasons.
+		 * 1. On 32-bit platforms could run out of vaddr.
+		 * 2. On boxes with a lot of CPUs we might have not enough
+		 *    memory to fit thd_t into VARIABLE_ARRAY.
+		 */
+		nthreads = 16;
 	}
 	VARIABLE_ARRAY(thd_t, threads, nthreads);
 	for (unsigned i = 0; i < nthreads; i++) {