Re: [PATCH] selftests/mm: compaction_test: Support platform with huge mount of memory

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2025/4/23 18:36, Feng Tang wrote:
> When running mm selftest to verify mm patches, 'compaction_test' case
> failed on an x86 server with 1TB memory. And the root cause is that it
> has too much free memory than what the test supports.
> 
> The test case tries to allocate 100000 huge pages, which is about 200 GB
> for that x86 server, and when it succeeds, it expects it's large than
> 1/3 of 80% of the free memory in system. This logic only works for
> platform with 750 GB ( 200 / (1/3) / 80% ) or less free memory, and may
> raise false alarm for others.
> 
> Fix it by changing the fixed page number to self-adjustable number
> according to the real number of free memory.
> 
> Fixes: bd67d5c15cc19 ("Test compaction of mlocked memory")
> Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>

Make sense to me. I tested it and passed on my platform. So:
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@inux.alibaba.com>

> ---
>   tools/testing/selftests/mm/compaction_test.c | 19 ++++++++++++++-----
>   1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c
> index 2c3a0eb6b22d..9bc4591c7b16 100644
> --- a/tools/testing/selftests/mm/compaction_test.c
> +++ b/tools/testing/selftests/mm/compaction_test.c
> @@ -90,6 +90,8 @@ int check_compaction(unsigned long mem_free, unsigned long hugepage_size,
>   	int compaction_index = 0;
>   	char nr_hugepages[20] = {0};
>   	char init_nr_hugepages[24] = {0};
> +	char target_nr_hugepages[24] = {0};
> +	int slen;
>   
>   	snprintf(init_nr_hugepages, sizeof(init_nr_hugepages),
>   		 "%lu", initial_nr_hugepages);
> @@ -106,11 +108,18 @@ int check_compaction(unsigned long mem_free, unsigned long hugepage_size,
>   		goto out;
>   	}
>   
> -	/* Request a large number of huge pages. The Kernel will allocate
> -	   as much as it can */
> -	if (write(fd, "100000", (6*sizeof(char))) != (6*sizeof(char))) {
> -		ksft_print_msg("Failed to write 100000 to /proc/sys/vm/nr_hugepages: %s\n",
> -			       strerror(errno));
> +	/*
> +	 * Request huge pages for about half of the free memory. The Kernel
> +	 * will allocate as much as it can, and we expect it will get at least 1/3
> +	 */
> +	nr_hugepages_ul = mem_free / hugepage_size / 2;
> +	snprintf(target_nr_hugepages, sizeof(target_nr_hugepages),
> +		 "%lu", nr_hugepages_ul);
> +
> +	slen = strlen(target_nr_hugepages);
> +	if (write(fd, target_nr_hugepages, slen) != slen) {
> +		ksft_print_msg("Failed to write %lu to /proc/sys/vm/nr_hugepages: %s\n",
> +			       nr_hugepages_ul, strerror(errno));
>   		goto close_fd;
>   	}
>