On Mon, Jun 30, 2025 at 11:08 AM Suresh K C
<[email protected]> wrote:
>
> From: Suresh K C <[email protected]>
>
> Add a test case to verify cachestat behavior with memory-mapped files
> using mmap(). This ensures that pages accessed via mmap are correctly
> accounted for in the page cache.
>
> Tested on x86_64 with default kernel config
>
> Signed-off-by: Suresh K C <[email protected]>
FWIW, the tests passed :)
> ---
> .../selftests/cachestat/test_cachestat.c | 39 ++++++++++++++++---
> 1 file changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/cachestat/test_cachestat.c
> b/tools/testing/selftests/cachestat/test_cachestat.c
> index 632ab44737ec..b6452978dae0 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);
> @@ -202,7 +207,7 @@ static int test_cachestat(const char *filename, bool
> write_random, bool create,
> return ret;
> }
>
> -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 +217,43 @@ 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 file.\n");
> ret = false;
> goto out;
> }
>
> if (ftruncate(fd, filesize)) {
> - ksft_print_msg("Unable to truncate shmem file.\n");
> + ksft_print_msg("Unable to truncate file.\n");
> ret = false;
> goto close_fd;
> }
>
> if (!write_exactly(fd, filesize)) {
> - ksft_print_msg("Unable to write to shmem file.\n");
> + ksft_print_msg("Unable to write to file.\n");
> ret = false;
> goto close_fd;
> }
>
> + if (type == 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';
> + }
> + map[filesize - 1] = 'X';
> + }
Joshua is right. We're already doing the write_exactly() for both
cases? Let's write_exactly() (i.e using the file descriptor-based
write syscall) only for FILE_SHMEM.
And why do we need the 'X' at the end?
