On Sat, May 24, 2025 at 1:36 AM Suresh K C
<suresh.k.chandra...@gmail.com> wrote:
>
> From: Suresh K C <suresh.k.chandra...@gmail.com>
>
> 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.
>
> Also add a test for /proc/cpuinfo to validate cachestat's handling of
> virtual files in pseudo-filesystems. This improves test coverage for
Hmm, it's been awhile since I wrote these tests, but isn't there
already a test for /proc/* files?
> edge cases involving non-regular files.
>
> Tested on x86_64 with default kernel config.
>
> Signed-off-by: Suresh K C <suresh.k.chandra...@gmail.com>
> ---
> .../selftests/cachestat/test_cachestat.c | 69 ++++++++++++++++++-
> 1 file changed, 67 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/cachestat/test_cachestat.c
> b/tools/testing/selftests/cachestat/test_cachestat.c
> index 632ab44737ec..81e7f6dd2279 100644
> --- a/tools/testing/selftests/cachestat/test_cachestat.c
> +++ b/tools/testing/selftests/cachestat/test_cachestat.c
> @@ -22,7 +22,7 @@
>
> static const char * const dev_files[] = {
> "/dev/zero", "/dev/null", "/dev/urandom",
> - "/proc/version", "/proc"
> + "/proc/version","/proc/cpuinfo","/proc"
> };
>
> void print_cachestat(struct cachestat *cs)
> @@ -202,6 +202,65 @@ static int test_cachestat(const char *filename, bool
> write_random, bool create,
> return ret;
> }
>
> +bool test_cachestat_mmap(void){
> +
> + size_t PS = sysconf(_SC_PAGESIZE);
> + size_t filesize = PS * 512 * 2;;
> + int syscall_ret;
> + size_t compute_len = PS * 512;
> + struct cachestat_range cs_range = { PS, compute_len };
> + char *filename = "tmpshmcstat";
> + unsigned long num_pages = compute_len / PS;
> + struct cachestat cs;
> + bool ret = true;
> + int fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666);
> + if (fd < 0) {
> + ksft_print_msg("Unable to create mmap file.\n");
> + ret = false;
> + goto out;
> + }
> + if (ftruncate(fd, filesize)) {
> + ksft_print_msg("Unable to truncate mmap file.\n");
> + ret = false;
> + goto close_fd;
> + }
> + if (!write_exactly(fd, filesize)) {
> + ksft_print_msg("Unable to write to mmap file.\n");
> + ret = false;
> + goto close_fd;
> + }
> + 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';
> +
> + syscall_ret = syscall(__NR_cachestat, fd, &cs_range, &cs, 0);
> +
> + if (syscall_ret) {
> + ksft_print_msg("Cachestat returned non-zero.\n");
> + ret = false;
> + } else {
> + print_cachestat(&cs);
> + if (cs.nr_cache + cs.nr_evicted != num_pages) {
> + ksft_print_msg("Total number of cached and evicted
> pages is off.\n");
> + ret = false;
> + }
> + }
> +
> +close_fd:
> + close(fd);
> + unlink(filename);
> +out:
> + return ret;
> +}
> +
This looks 90% the same as another test. Are we literally just adding
the mmap step to test_cachestat and call it a new test?
Can we at least refactor things?
