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Add support for cachestat() syscall #111

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Add support for cachestat() syscall #111

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59 changes: 53 additions & 6 deletions vmtouch.c
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Original file line number Diff line number Diff line change
Expand Up @@ -491,6 +491,42 @@ static int can_do_mincore(struct stat *st) {
(st->st_mode&S_IWOTH) ||
uid == 0;
}

#define __NR_cachestat 451

struct cachestat_range {
__u64 off;
__u64 len;
};

struct cachestat {
__u64 nr_cache;
__u64 nr_dirty;
__u64 nr_writeback;
__u64 nr_evicted;
__u64 nr_recently_evicted;
};

int cachestat(int fd, struct cachestat_range *cstat_range, struct cachestat *cstat, unsigned int flags) {
return syscall(__NR_cachestat, fd, cstat_range, cstat, flags);
}

int cachestat_supported() {
static enum {
UNKNOWN,
SUPPORTED,
UNSUPPORTED
} state = UNKNOWN;

if (state == UNKNOWN) {
if (cachestat(-1, NULL, NULL, 0) && errno == ENOSYS) {
state = UNSUPPORTED;
} else {
state = SUPPORTED;
}
}
return state == SUPPORTED;
}
#endif


Expand Down Expand Up @@ -572,19 +608,30 @@ void vmtouch_file(char *path) {
len_of_range = len_of_file - offset;
}

mem = mmap(NULL, len_of_range, PROT_READ, MAP_SHARED, fd, offset);
pages_in_range = bytes2pages(len_of_range);
total_pages += pages_in_range;

#if defined(__linux__)
if (!o_evict && !o_touch && !o_verbose && cachestat_supported()) {
struct cachestat cs;
struct cachestat_range cs_range = {
.off = offset,
.len = len_of_range
};
if (!cachestat(fd, &cs_range, &cs, 0)) {
total_pages_in_core += cs.nr_cache;
goto bail;
}
}
#endif

mem = mmap(NULL, len_of_range, PROT_READ, MAP_SHARED, fd, offset);
if (mem == MAP_FAILED) {
warning("unable to mmap file %s (%s), skipping", path, strerror(errno));
goto bail;
}

if (!aligned_p(mem)) fatal("mmap(%s) wasn't page aligned", path);

pages_in_range = bytes2pages(len_of_range);

total_pages += pages_in_range;

if (o_evict) {
if (o_verbose) printf("Evicting %s\n", path);

Expand Down