RE: [External] [RFC 1/7] lib/test_vmalloc: Add non-block-alloc-test case

[Adrian Huang12 <ahuang12@lenovo.com>]

Hi Uladzislau,

> -----Original Message-----
> From: owner-linux-mm@kvack.org <owner-linux-mm@kvack.org> On Behalf
> Of Uladzislau Rezki (Sony)
> Sent: Friday, July 4, 2025 11:26 PM
> To: linux-mm@kvack.org; Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@kernel.org>; LKML
> <linux-kernel@vger.kernel.org>; Baoquan He <bhe@redhat.com>; Uladzislau
> Rezki <urezki@gmail.com>
> Subject: [External] [RFC 1/7] lib/test_vmalloc: Add non-block-alloc-test case
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---
>  lib/test_vmalloc.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c index
> 1b0b59549aaf..9e3429dfe176 100644
> --- a/lib/test_vmalloc.c
> +++ b/lib/test_vmalloc.c
> @@ -54,6 +54,7 @@ __param(int, run_test_mask, INT_MAX,
>  		"\t\tid: 256,  name: kvfree_rcu_1_arg_vmalloc_test\n"
>  		"\t\tid: 512,  name: kvfree_rcu_2_arg_vmalloc_test\n"
>  		"\t\tid: 1024, name: vm_map_ram_test\n"
> +		"\t\tid: 2048, name: no_block_alloc_test\n"
>  		/* Add a new test case description here. */  );
> 
> @@ -283,6 +284,31 @@ static int fix_size_alloc_test(void)
>  	return 0;
>  }
> 
> +static DEFINE_SPINLOCK(no_block_alloc_lock);
> +
> +static int no_block_alloc_test(void)
> +{
> +	void *ptr;
> +	u8 rnd;
> +	int i;
> +
> +	for (i = 0; i < test_loop_count; i++) {
> +		rnd = get_random_u8();
> +
> +		spin_lock(&no_block_alloc_lock);

Since there is no shared data to be protected, do we need this lock for serialization? Any concerns?

It spent 18 minutes for this test (256-core server):
  # time modprobe test_vmalloc nr_threads=$(nproc) run_test_mask=0x800
  real    18m6.099s
  user    0m0.002s
  sys     0m4.555s

Without the lock, it spent 41 seconds (Have run for 300+ tests without any failure: 256-core server):
  # time modprobe test_vmalloc nr_threads=$(nproc) run_test_mask=0x800
  real    0m41.367s
  user    0m0.003s
  sys     0m5.758s

Would it be better to run this test concurrently? That said, it can also verify the scalability problem when the number of CPUs grow. 

> +		ptr = __vmalloc(PAGE_SIZE, (rnd % 2) ? GFP_NOWAIT :
> GFP_ATOMIC);
> +		spin_unlock(&no_block_alloc_lock);
> +
> +		if (!ptr)
> +			return -1;
> +
> +		*((__u8 *)ptr) = 0;
> +		vfree(ptr);
> +	}
> +
> +	return 0;
> +}
> +
>  static int
>  pcpu_alloc_test(void)
>  {
> @@ -410,6 +436,7 @@ static struct test_case_desc test_case_array[] = {
>  	{ "kvfree_rcu_1_arg_vmalloc_test", kvfree_rcu_1_arg_vmalloc_test },
>  	{ "kvfree_rcu_2_arg_vmalloc_test", kvfree_rcu_2_arg_vmalloc_test },
>  	{ "vm_map_ram_test", vm_map_ram_test },
> +	{ "no_block_alloc_test", no_block_alloc_test },
>  	/* Add a new test case here. */
>  };
> 
> --
> 2.39.5
>