tools/vm/page-types.c: page-cache sniffing feature

After this patch 'page-types' can walk over a file's mappings and
analyze populated page cache pages mostly without disturbing its state.

It maps chunk of file, marks VMA as MADV_RANDOM to turn off readahead,
pokes VMA via mincore() to determine cached pages, triggers page-fault
only for them, and finally gathers information via pagemap/kpageflags.
Before unmap it marks VMA as MADV_SEQUENTIAL for ignoring reference
bits.

usage: page-types -f <path>

If <path> is directory it will analyse all files in all subdirectories.

Symlinks are not followed as well as mount points.  Hardlinks aren't
handled, they'll be dumped as many times as they are found.  Recursive
walk brings all dentries into dcache and populates page cache of
block-devices aka 'Buffers'.

Probably it's worth to add ioctl for dumping file page cache as array of
PFNs as a replacement for this hackish juggling with
mmap/madvise/mincore/pagemap.  Also recursive walk could be replaced
with dumping cached inodes via some ioctl or debugfs interface followed
by openning them via open_by_handle_at, this would fix hardlinks
handling and unneeded population of dcache and buffers.  This interface
might be used as data source for constructing readahead plans and for
background optimizations of actively used files.

collateral changes:
+ fix 64-bit LFS: define _FILE_OFFSET_BITS instead of _LARGEFILE64_SOURCE
+ replace lseek + read with single pread
+ make show_page_range() reusable after flush

usage example:

  ~/src/linux/tools/vm$ sudo ./page-types -L -f page-types
  foffset offset    flags
  page-types       Inode: 2229277       Size: 89065 (22 pages)
  Modify: Tue Feb 25 12:00:59 2014 (162 seconds ago)
  Access: Tue Feb 25 12:01:00 2014 (161 seconds ago)
  0       3cbf3b     __RU_lA____M________________________
  1       38946a     __RU_lA____M________________________
  2       1a3cec     __RU_lA____M________________________
  3       1a8321     __RU_lA____M________________________
  4       3af7cc     __RU_lA____M________________________
  5       1ed532     __RU_lA_____________________________
  6       2e436a     __RU_lA_____________________________
  7       29a35e     ___U_lA_____________________________
  8       2de86e     ___U_lA_____________________________
  9       3bdfb4     ___U_lA_____________________________
  10      3cd8a3     ___U_lA_____________________________
  11      2afa50     ___U_lA_____________________________
  12      2534c2     ___U_lA_____________________________
  13      1b7a40     ___U_lA_____________________________
  14      17b0be     ___U_lA_____________________________
  15      392b0c     ___U_lA_____________________________
  16      3ba46a     __RU_lA_____________________________
  17      397dc8     ___U_lA_____________________________
  18      1f2a36     ___U_lA_____________________________
  19      21fd30     __RU_lA_____________________________
  20      2c35ba     __RU_l______________________________
  21      20f181     __RU_l______________________________

               flags page-count   MB  symbolic-flags                        long-symbolic-flags
  0x000000000000002c          2    0  __RU_l______________________________  referenced,uptodate,lru
  0x0000000000000068         11    0  ___U_lA_____________________________  uptodate,lru,active
  0x000000000000006c          4    0  __RU_lA_____________________________  referenced,uptodate,lru,active
  0x000000000000086c          5    0  __RU_lA____M________________________  referenced,uptodate,lru,active,mmap
               total         22    0

  ~/src/linux/tools/vm$ sudo ./page-types -f /
               flags page-count     MB  symbolic-flags                        long-symbolic-flags
  0x0000000000000028      21761     85  ___U_l______________________________  uptodate,lru
  0x000000000000002c     127279    497  __RU_l______________________________  referenced,uptodate,lru
  0x0000000000000068      74160    289  ___U_lA_____________________________  uptodate,lru,active
  0x000000000000006c      84469    329  __RU_lA_____________________________  referenced,uptodate,lru,active
  0x000000000000007c          1      0  __RUDlA_____________________________  referenced,uptodate,dirty,lru,active
  0x0000000000000228        370      1  ___U_l___I__________________________  uptodate,lru,reclaim
  0x0000000000000828         49      0  ___U_l_____M________________________  uptodate,lru,mmap
  0x000000000000082c        126      0  __RU_l_____M________________________  referenced,uptodate,lru,mmap
  0x0000000000000868        137      0  ___U_lA____M________________________  uptodate,lru,active,mmap
  0x000000000000086c      12890     50  __RU_lA____M________________________  referenced,uptodate,lru,active,mmap
               total     321242   1254
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/vm/page-types.c

@@ -19,7 +19,8 @@
  * Authors: Wu Fengguang <fengguang.wu@intel.com>
  */
 
-#define _LARGEFILE64_SOURCE
+#define _FILE_OFFSET_BITS 64
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -29,11 +30,14 @@
 #include <getopt.h>
 #include <limits.h>
 #include <assert.h>
+#include <ftw.h>
+#include <time.h>
 #include <sys/types.h>
 #include <sys/errno.h>
 #include <sys/fcntl.h>
 #include <sys/mount.h>
 #include <sys/statfs.h>
+#include <sys/mman.h>
 #include "../../include/uapi/linux/magic.h"
 #include "../../include/uapi/linux/kernel-page-flags.h"
 #include <api/fs/debugfs.h>
@@ -158,6 +162,7 @@ static int		opt_raw;	/* for kernel developers */
 static int		opt_list;	/* list pages (in ranges) */
 static int		opt_no_summary;	/* don't show summary */
 static pid_t		opt_pid;	/* process to walk */
+const char *		opt_file;
 
 #define MAX_ADDR_RANGES	1024
 static int		nr_addr_ranges;
@@ -253,12 +258,7 @@ static unsigned long do_u64_read(int fd, char *name,
 	if (index > ULONG_MAX / 8)
 		fatal("index overflow: %lu\n", index);
 
-	if (lseek(fd, index * 8, SEEK_SET) < 0) {
-		perror(name);
-		exit(EXIT_FAILURE);
-	}
-
-	bytes = read(fd, buf, count * 8);
+	bytes = pread(fd, buf, count * 8, (off_t)index * 8);
 	if (bytes < 0) {
 		perror(name);
 		exit(EXIT_FAILURE);
@@ -343,8 +343,8 @@ static char *page_flag_longname(uint64_t flags)
  * page list and summary
  */
 
-static void show_page_range(unsigned long voffset,
-			    unsigned long offset, uint64_t flags)
+static void show_page_range(unsigned long voffset, unsigned long offset,
+			    unsigned long size, uint64_t flags)
 {
 	static uint64_t      flags0;
 	static unsigned long voff;
@@ -352,14 +352,16 @@ static void show_page_range(unsigned long voffset,
 	static unsigned long count;
 
 	if (flags == flags0 && offset == index + count &&
-	    (!opt_pid || voffset == voff + count)) {
-		count++;
+	    size && voffset == voff + count) {
+		count += size;
 		return;
 	}
 
 	if (count) {
 		if (opt_pid)
 			printf("%lx\t", voff);
+		if (opt_file)
+			printf("%lu\t", voff);
 		printf("%lx\t%lx\t%s\n",
 				index, count, page_flag_name(flags0));
 	}
@@ -367,7 +369,12 @@ static void show_page_range(unsigned long voffset,
 	flags0 = flags;
 	index  = offset;
 	voff   = voffset;
-	count  = 1;
+	count  = size;
+}
+
+static void flush_page_range(void)
+{
+	show_page_range(0, 0, 0, 0);
 }
 
 static void show_page(unsigned long voffset,
@@ -375,6 +382,8 @@ static void show_page(unsigned long voffset,
 {
 	if (opt_pid)
 		printf("%lx\t", voffset);
+	if (opt_file)
+		printf("%lu\t", voffset);
 	printf("%lx\t%s\n", offset, page_flag_name(flags));
 }
 
@@ -565,7 +574,7 @@ static void add_page(unsigned long voffset,
 		unpoison_page(offset);
 
 	if (opt_list == 1)
-		show_page_range(voffset, offset, flags);
+		show_page_range(voffset, offset, 1, flags);
 	else if (opt_list == 2)
 		show_page(voffset, offset, flags);
 
@@ -667,7 +676,7 @@ static void walk_addr_ranges(void)
 
 	for (i = 0; i < nr_addr_ranges; i++)
 		if (!opt_pid)
-			walk_pfn(0, opt_offset[i], opt_size[i], 0);
+			walk_pfn(opt_offset[i], opt_offset[i], opt_size[i], 0);
 		else
 			walk_task(opt_offset[i], opt_size[i]);
 
@@ -699,9 +708,7 @@ static void usage(void)
 "            -a|--addr    addr-spec     Walk a range of pages\n"
 "            -b|--bits    bits-spec     Walk pages with specified bits\n"
 "            -p|--pid     pid           Walk process address space\n"
-#if 0 /* planned features */
 "            -f|--file    filename      Walk file address space\n"
-#endif
 "            -l|--list                  Show page details in ranges\n"
 "            -L|--list-each             Show page details one by one\n"
 "            -N|--no-summary            Don't show summary info\n"
@@ -799,8 +806,130 @@ static void parse_pid(const char *str)
 	fclose(file);
 }
 
+static void show_file(const char *name, const struct stat *st)
+{
+	unsigned long long size = st->st_size;
+	char atime[64], mtime[64];
+	long now = time(NULL);
+
+	printf("%s\tInode: %u\tSize: %llu (%llu pages)\n",
+			name, (unsigned)st->st_ino,
+			size, (size + page_size - 1) / page_size);
+
+	strftime(atime, sizeof(atime), "%c", localtime(&st->st_atime));
+	strftime(mtime, sizeof(mtime), "%c", localtime(&st->st_mtime));
+
+	printf("Modify: %s (%ld seconds ago)\nAccess: %s (%ld seconds ago)\n",
+			mtime, now - st->st_mtime,
+			atime, now - st->st_atime);
+}
+
+static void walk_file(const char *name, const struct stat *st)
+{
+	uint8_t vec[PAGEMAP_BATCH];
+	uint64_t buf[PAGEMAP_BATCH], flags;
+	unsigned long nr_pages, pfn, i;
+	int fd;
+	off_t off;
+	ssize_t len;
+	void *ptr;
+	int first = 1;
+
+	fd = checked_open(name, O_RDONLY|O_NOATIME|O_NOFOLLOW);
+
+	for (off = 0; off < st->st_size; off += len) {
+		nr_pages = (st->st_size - off + page_size - 1) / page_size;
+		if (nr_pages > PAGEMAP_BATCH)
+			nr_pages = PAGEMAP_BATCH;
+		len = nr_pages * page_size;
+
+		ptr = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, off);
+		if (ptr == MAP_FAILED)
+			fatal("mmap failed: %s", name);
+
+		/* determine cached pages */
+		if (mincore(ptr, len, vec))
+			fatal("mincore failed: %s", name);
+
+		/* turn off readahead */
+		if (madvise(ptr, len, MADV_RANDOM))
+			fatal("madvice failed: %s", name);
+
+		/* populate ptes */
+		for (i = 0; i < nr_pages ; i++) {
+			if (vec[i] & 1)
+				(void)*(volatile int *)(ptr + i * page_size);
+		}
+
+		/* turn off harvesting reference bits */
+		if (madvise(ptr, len, MADV_SEQUENTIAL))
+			fatal("madvice failed: %s", name);
+
+		if (pagemap_read(buf, (unsigned long)ptr / page_size,
+					nr_pages) != nr_pages)
+			fatal("cannot read pagemap");
+
+		munmap(ptr, len);
+
+		for (i = 0; i < nr_pages; i++) {
+			pfn = pagemap_pfn(buf[i]);
+			if (!pfn)
+				continue;
+			if (!kpageflags_read(&flags, pfn, 1))
+				continue;
+			if (first && opt_list) {
+				first = 0;
+				flush_page_range();
+				show_file(name, st);
+			}
+			add_page(off / page_size + i, pfn, flags, buf[i]);
+		}
+	}
+
+	close(fd);
+}
+
+int walk_tree(const char *name, const struct stat *st, int type, struct FTW *f)
+{
+	(void)f;
+	switch (type) {
+	case FTW_F:
+		if (S_ISREG(st->st_mode))
+			walk_file(name, st);
+		break;
+	case FTW_DNR:
+		fprintf(stderr, "cannot read dir: %s\n", name);
+		break;
+	}
+	return 0;
+}
+
+static void walk_page_cache(void)
+{
+	struct stat st;
+
+	kpageflags_fd = checked_open(PROC_KPAGEFLAGS, O_RDONLY);
+	pagemap_fd = checked_open("/proc/self/pagemap", O_RDONLY);
+
+	if (stat(opt_file, &st))
+		fatal("stat failed: %s\n", opt_file);
+
+	if (S_ISREG(st.st_mode)) {
+		walk_file(opt_file, &st);
+	} else if (S_ISDIR(st.st_mode)) {
+		/* do not follow symlinks and mountpoints */
+		if (nftw(opt_file, walk_tree, 64, FTW_MOUNT | FTW_PHYS) < 0)
+			fatal("nftw failed: %s\n", opt_file);
+	} else
+		fatal("unhandled file type: %s\n", opt_file);
+
+	close(kpageflags_fd);
+	close(pagemap_fd);
+}
+
 static void parse_file(const char *name)
 {
+	opt_file = name;
 }
 
 static void parse_addr_range(const char *optarg)
@@ -991,15 +1120,20 @@ int main(int argc, char *argv[])
 
 	if (opt_list && opt_pid)
 		printf("voffset\t");
+	if (opt_list && opt_file)
+		printf("foffset\t");
 	if (opt_list == 1)
 		printf("offset\tlen\tflags\n");
 	if (opt_list == 2)
 		printf("offset\tflags\n");
 
+	if (opt_file)
+		walk_page_cache();
+	else
 		walk_addr_ranges();
 
 	if (opt_list == 1)
-		show_page_range(0, 0, 0);  /* drain the buffer */
+		flush_page_range();
 
 	if (opt_no_summary)
 		return 0;