[PATCH 7/7] mm: huge_memory: enable debugfs to split huge pages to any order.
From: Zi Yan
Date: Thu Nov 19 2020 - 11:06:45 EST
From: Zi Yan <ziy@xxxxxxxxxx>
It is used to test split_huge_page_to_list_to_order for pagecache THPs.
Also add test cases for split_huge_page_to_list_to_order via both
debugfs, truncating a file, and punching holes in a file.
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
mm/huge_memory.c | 13 +-
.../selftests/vm/split_huge_page_test.c | 192 ++++++++++++++++--
2 files changed, 186 insertions(+), 19 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index cc70f70862d8..d6ce7be65fb2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2999,7 +2999,7 @@ static ssize_t split_huge_pages_in_range_pid_write(struct file *file,
static DEFINE_MUTEX(mutex);
ssize_t ret;
char input_buf[80]; /* hold pid, start_vaddr, end_vaddr */
- int pid;
+ int pid, to_order = 0;
unsigned long vaddr_start, vaddr_end, addr;
nodemask_t task_nodes;
struct mm_struct *mm;
@@ -3016,8 +3016,9 @@ static ssize_t split_huge_pages_in_range_pid_write(struct file *file,
goto out;
input_buf[79] = '\0';
- ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
- if (ret != 3) {
+ ret = sscanf(input_buf, "%d,0x%lx,0x%lx,%d", &pid, &vaddr_start, &vaddr_end, &to_order);
+ /* cannot split to order-1 THP, which is not possible */
+ if ((ret != 3 && ret != 4) || to_order == 1) {
ret = -EINVAL;
goto out;
}
@@ -3025,8 +3026,8 @@ static ssize_t split_huge_pages_in_range_pid_write(struct file *file,
vaddr_end &= PAGE_MASK;
ret = strlen(input_buf);
- pr_debug("split huge pages in pid: %d, vaddr: [%lx - %lx]\n",
- pid, vaddr_start, vaddr_end);
+ pr_debug("split huge pages in pid: %d, vaddr: [%lx - %lx], to order: %d\n",
+ pid, vaddr_start, vaddr_end, to_order);
mm = find_mm_struct(pid, &task_nodes);
if (IS_ERR(mm)) {
@@ -3066,7 +3067,7 @@ static ssize_t split_huge_pages_in_range_pid_write(struct file *file,
if (!trylock_page(page))
continue;
- if (!split_huge_page(page))
+ if (!split_huge_page_to_list_to_order(page, NULL, to_order))
split++;
unlock_page(page);
diff --git a/tools/testing/selftests/vm/split_huge_page_test.c b/tools/testing/selftests/vm/split_huge_page_test.c
index cd2ced8c1261..bfd35ae9cfd2 100644
--- a/tools/testing/selftests/vm/split_huge_page_test.c
+++ b/tools/testing/selftests/vm/split_huge_page_test.c
@@ -16,6 +16,7 @@
#include <sys/wait.h>
#include <malloc.h>
#include <stdbool.h>
+#include <time.h>
uint64_t pagesize;
unsigned int pageshift;
@@ -24,6 +25,7 @@ uint64_t pmd_pagesize;
#define PMD_SIZE_PATH "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size"
#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages_in_range_pid"
#define SMAP_PATH "/proc/self/smaps"
+#define THP_FS_PATH "/mnt/thp_fs"
#define INPUT_MAX 80
#define PFN_MASK ((1UL<<55)-1)
@@ -89,19 +91,20 @@ static int write_file(const char *path, const char *buf, size_t buflen)
return (unsigned int) numwritten;
}
-static void write_debugfs(int pid, uint64_t vaddr_start, uint64_t vaddr_end)
+static void write_debugfs(int pid, uint64_t vaddr_start, uint64_t vaddr_end, int order)
{
char input[INPUT_MAX];
int ret;
- ret = snprintf(input, INPUT_MAX, "%d,0x%lx,0x%lx", pid, vaddr_start,
- vaddr_end);
+ ret = snprintf(input, INPUT_MAX, "%d,0x%lx,0x%lx,%d", pid, vaddr_start,
+ vaddr_end, order);
if (ret >= INPUT_MAX) {
printf("%s: Debugfs input is too long\n", __func__);
exit(EXIT_FAILURE);
}
- if (!write_file(SPLIT_DEBUGFS, input, ret + 1)) {
+ /* order == 1 is an invalid input that should be detected. */
+ if (order != 1 && !write_file(SPLIT_DEBUGFS, input, ret + 1)) {
perror(SPLIT_DEBUGFS);
exit(EXIT_FAILURE);
}
@@ -118,7 +121,7 @@ static bool check_for_pattern(FILE *fp, const char *pattern, char *buf)
return false;
}
-static uint64_t check_huge(void *addr)
+static uint64_t check_huge(void *addr, const char *prefix)
{
uint64_t thp = 0;
int ret;
@@ -143,13 +146,13 @@ static uint64_t check_huge(void *addr)
goto err_out;
/*
- * Fetch the AnonHugePages: in the same block and check the number of
+ * Fetch the @prefix in the same block and check the number of
* hugepages.
*/
- if (!check_for_pattern(fp, "AnonHugePages:", buffer))
+ if (!check_for_pattern(fp, prefix, buffer))
goto err_out;
- if (sscanf(buffer, "AnonHugePages:%10ld kB", &thp) != 1) {
+ if (sscanf(&buffer[strlen(prefix)], "%10ld kB", &thp) != 1) {
printf("Reading smap error\n");
exit(EXIT_FAILURE);
}
@@ -173,14 +176,14 @@ void split_pmd_thp(void)
for (i = 0; i < len; i++)
one_page[i] = (char)i;
- thp_size = check_huge(one_page);
+ thp_size = check_huge(one_page, "AnonHugePages:");
if (!thp_size) {
printf("No THP is allocatd");
exit(EXIT_FAILURE);
}
/* split all possible huge pages */
- write_debugfs(getpid(), (uint64_t)one_page, (uint64_t)one_page + len);
+ write_debugfs(getpid(), (uint64_t)one_page, (uint64_t)one_page + len, 0);
for (i = 0; i < len; i++)
if (one_page[i] != (char)i) {
@@ -189,7 +192,7 @@ void split_pmd_thp(void)
}
- thp_size = check_huge(one_page);
+ thp_size = check_huge(one_page, "AnonHugePages:");
if (thp_size) {
printf("Still %ld kB AnonHugePages not split\n", thp_size);
exit(EXIT_FAILURE);
@@ -237,7 +240,7 @@ void split_pte_mapped_thp(void)
for (i = 0; i < len; i++)
one_page[i] = (char)i;
- thp_size = check_huge(one_page);
+ thp_size = check_huge(one_page, "AnonHugePages:");
if (!thp_size) {
printf("No THP is allocatd");
exit(EXIT_FAILURE);
@@ -270,7 +273,7 @@ void split_pte_mapped_thp(void)
/* split all possible huge pages */
write_debugfs(getpid(), (uint64_t)pte_mapped,
- (uint64_t)pte_mapped + pagesize * 4);
+ (uint64_t)pte_mapped + pagesize * 4, 0);
/* smap does not show THPs after mremap, use kpageflags instead */
thp_size = 0;
@@ -295,19 +298,182 @@ void split_pte_mapped_thp(void)
close(kpageflags_fd);
}
+void create_pagecache_thp_and_fd(size_t fd_size, int *fd, char **addr)
+{
+ const char testfile[] = THP_FS_PATH "/test";
+ size_t i;
+ int dummy;
+
+ srand(time(NULL));
+
+ *fd = open(testfile, O_CREAT | O_RDWR, 0664);
+ if (*fd == -1) {
+ perror("Failed to create a file at "THP_FS_PATH);
+ exit(EXIT_FAILURE);
+ }
+
+ for (i = 0; i < fd_size; i++) {
+ unsigned char byte = (unsigned char)i;
+
+ write(*fd, &byte, sizeof(byte));
+ }
+ close(*fd);
+ sync();
+ *fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
+ if (*fd == -1) {
+ perror("open drop_caches");
+ exit(EXIT_FAILURE);
+ }
+ if (write(*fd, "3", 1) != 1) {
+ perror("write to drop_caches");
+ exit(EXIT_FAILURE);
+ }
+ close(*fd);
+
+ *fd = open(testfile, O_RDWR);
+ if (*fd == -1) {
+ perror("Failed to open a file at "THP_FS_PATH);
+ exit(EXIT_FAILURE);
+ }
+
+ *addr = mmap(NULL, fd_size, PROT_READ|PROT_WRITE, MAP_SHARED, *fd, 0);
+ if (*addr == (char *)-1) {
+ perror("cannot mmap");
+ exit(1);
+ }
+ madvise(*addr, fd_size, MADV_HUGEPAGE);
+
+ for (size_t i = 0; i < fd_size; i++)
+ dummy += *(*addr + i);
+
+ if (!check_huge(*addr, "FilePmdMapped:")) {
+ printf("No pagecache THP generated, please mount a filesystem "
+ "supporting pagecache THP at "THP_FS_PATH"\n");
+ exit(EXIT_FAILURE);
+ }
+}
+
+void split_thp_in_pagecache_to_order(size_t fd_size, int order)
+{
+ int fd;
+ char *addr;
+ size_t i;
+
+ create_pagecache_thp_and_fd(fd_size, &fd, &addr);
+
+ printf("split %ld kB pagecache page to order %d ... ", fd_size >> 10, order);
+ write_debugfs(getpid(), (uint64_t)addr, (uint64_t)addr + fd_size, order);
+
+ for (i = 0; i < fd_size; i++)
+ if (*(addr + i) != (char)i) {
+ printf("%lu byte corrupted in the file\n");
+ exit(EXIT_FAILURE);
+ }
+
+ close(fd);
+ printf("done\n");
+}
+
+void truncate_thp_in_pagecache_to_order(size_t fd_size, int order)
+{
+ int fd;
+ char *addr;
+ size_t i;
+
+ create_pagecache_thp_and_fd(fd_size, &fd, &addr);
+
+ printf("truncate %ld kB pagecache page to size %lu kB ... ", fd_size >> 10, 4UL << order);
+ ftruncate(fd, pagesize << order);
+
+ for (i = 0; i < (pagesize << order); i++)
+ if (*(addr + i) != (char)i) {
+ printf("%lu byte corrupted in the file\n");
+ exit(EXIT_FAILURE);
+ }
+
+ close(fd);
+ printf("done\n");
+}
+
+void punch_hole_in_pagecache_thp(size_t fd_size, off_t offset[], off_t len[], int n)
+{
+ int fd, j;
+ char *addr;
+ size_t i;
+
+ create_pagecache_thp_and_fd(fd_size, &fd, &addr);
+
+ for (j = 0; j < n; j++) {
+ printf("addr: %lx, punch a hole at offset %ld kB with len %ld kB ... ",
+ addr, offset[j] >> 10, len[j] >> 10);
+ fallocate(fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, offset[j], len[j]);
+ printf("done\n");
+ }
+
+ for (i = 0; i < fd_size; i++) {
+ int in_hole = 0;
+
+ for (j = 0; j < n; j++)
+ if (i >= offset[j] && i <= (offset[j] + len[j])) {
+ in_hole = 1;
+ break;
+ }
+
+ if (in_hole)
+ continue;
+ if (*(addr + i) != (char)i) {
+ printf("%lu byte corrupted in the file\n", i);
+ exit(EXIT_FAILURE);
+ }
+ }
+
+ close(fd);
+
+}
+
int main(int argc, char **argv)
{
+ int i;
+ size_t fd_size;
+ off_t offset[2], len[2];
+
if (geteuid() != 0) {
printf("Please run the benchmark as root\n");
exit(EXIT_FAILURE);
}
+ setbuf(stdout, NULL);
+
pagesize = getpagesize();
pageshift = ffs(pagesize) - 1;
pmd_pagesize = read_pmd_pagesize();
+ fd_size = 2 * pmd_pagesize;
split_pmd_thp();
split_pte_mapped_thp();
+ for (i = 8; i >= 0; i--)
+ split_thp_in_pagecache_to_order(fd_size, i);
+
+ /*
+ * for i is 1, truncate code in the kernel should create order-0 pages
+ * instead of order-1 THPs, since order-1 THP is not supported. No error
+ * is expected.
+ */
+ for (i = 8; i >= 0; i--)
+ truncate_thp_in_pagecache_to_order(fd_size, i);
+
+ offset[0] = 123 * pagesize;
+ offset[1] = 4 * pagesize;
+ len[0] = 200 * pagesize;
+ len[1] = 16 * pagesize;
+ punch_hole_in_pagecache_thp(fd_size, offset, len, 2);
+
+ offset[0] = 259 * pagesize;
+ offset[1] = 33 * pagesize;
+ len[0] = 129 * pagesize;
+ len[1] = 16 * pagesize;
+ punch_hole_in_pagecache_thp(fd_size, offset, len, 2);
+
return 0;
}
--
2.28.0