Re: [PATCH v3] selftests: cachestat: add tests for mmap Refactor and enhance mmap test for cachestat validation

On Wed, Jul 9, 2025 at 10:47 AM Suresh K C suresh.k.chandrappa@gmail.com wrote:

From: Suresh K C suresh.k.chandrappa@gmail.com

This patch merges the previous two patches into a single, cohesive test case that verifies cachestat behavior with memory-mapped files using mmap(). It also refactors the test logic to reduce redundancy, improve error reporting, and clarify failure messages for both shmem and mmap file types.

Changes since v2:

• Merged the two patches into one as suggested
• Improved error messages for better clarity

Tested on x86_64 with default kernel config.

Signed-off-by: Suresh K C suresh.k.chandrappa@gmail.com

.../selftests/cachestat/test_cachestat.c | 66 +++++++++++++++---- 1 file changed, 55 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/cachestat/test_cachestat.c b/tools/testing/selftests/cachestat/test_cachestat.c index 632ab44737ec..18188d7c639e 100644 --- a/tools/testing/selftests/cachestat/test_cachestat.c +++ b/tools/testing/selftests/cachestat/test_cachestat.c @@ -33,6 +33,11 @@ void print_cachestat(struct cachestat *cs) cs->nr_evicted, cs->nr_recently_evicted); }

+enum file_type {

•   FILE_MMAP,
  

•   FILE_SHMEM
  

+};

bool write_exactly(int fd, size_t filesize) { int random_fd = open("/dev/urandom", O_RDONLY); @@ -201,8 +206,19 @@ static int test_cachestat(const char *filename, bool write_random, bool create, out: return ret; } +const char* file_type_str(enum file_type type) {

•   switch (type) {
  

•           case FILE_SHMEM:
  

•                   return "shmem";
  

•           case FILE_MMAP:
  

•                   return "mmap";
  

•           default:
  

•                   return "unknown";
  

•   }
  

+}

-bool test_cachestat_shmem(void)

+bool run_cachestat_test(enum file_type type) { size_t PS = sysconf(_SC_PAGESIZE); size_t filesize = PS * 512 * 2; /* 2 2MB huge pages */ @@ -212,27 +228,49 @@ bool test_cachestat_shmem(void) char *filename = "tmpshmcstat"; struct cachestat cs; bool ret = true;

•   int fd;
    unsigned long num_pages = compute_len / PS;
  

•   int fd = shm_open(filename, O_CREAT | O_RDWR, 0600);
  

•   if (type == FILE_SHMEM)
  

•           fd = shm_open(filename, O_CREAT | O_RDWR, 0600);
  

•   else
  

•           fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666);
  
    if (fd < 0) {
  

•           ksft_print_msg("Unable to create shmem file.\n");
  

•           ksft_print_msg("Unable to create %s file.\n",file_type_str(type));
            ret = false;
            goto out;
    }
  
    if (ftruncate(fd, filesize)) {
  

•           ksft_print_msg("Unable to truncate shmem file.\n");
  

•           ksft_print_msg("Unable to truncate %s file.\n",file_type_str(type));
            ret = false;
            goto close_fd;
    }
  

•   if (!write_exactly(fd, filesize)) {
  

•           ksft_print_msg("Unable to write to shmem file.\n");
  

•           ret = false;
  

•           goto close_fd;
  

•   switch (type){
  

•           case FILE_SHMEM:
  

•                   if (!write_exactly(fd, filesize)) {
  

•                           ksft_print_msg("Unable to write to file.\n");
  

•                           ret = false;
  

•                           goto close_fd;
  

•                   }
  

•                   break;
  

•           case FILE_MMAP:
  

•                   char *map = mmap(NULL, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  

•                   if (map == MAP_FAILED) {
  

•                           ksft_print_msg("mmap failed.\n");
  

•                           ret = false;
  

•                           goto close_fd;
  

•                   }
  

•                   for (int i = 0; i < filesize; i++) {
  

•                           map[i] = 'A';
  

•                   }
  

•                   break;
  

•           default:
  

•                   ksft_print_msg("Unsupported file type.\n");
  

•                   ret = false;
  

•                   goto close_fd;
  

•                   break;
    }
  

•   syscall_ret = syscall(__NR_cachestat, fd, &cs_range, &cs, 0);
  
    if (syscall_ret) {
  

@@ -308,12 +346,18 @@ int main(void) break; }

•   if (test_cachestat_shmem())
  

•   if (run_cachestat_test(FILE_SHMEM))
            ksft_test_result_pass("cachestat works with a shmem file\n");
    else {
            ksft_test_result_fail("cachestat fails with a shmem file\n");
            ret = 1;
    }
  
  

•   if (run_cachestat_test(FILE_MMAP))
  

•           ksft_test_result_pass("cachestat works with a mmap file\n");
  

•   else {
  

•           ksft_test_result_fail("cachestat fails with a mmap file\n");
  

•           ret = 1;
  

•   }
    return ret;
  

}

2.43.0

Code LGTM, and the test passed on my system (x86-64 too though). FWIW:

Tested-by: Nhat Pham nphamcs@gmail.com Acked-by: Nhat Pham nphamcs@gmail.com

Thanks for the test contribution, Suresh! And thanks for the review help, Joshua :)