On 3/4/25 09:10, Jaegeuk Kim via Linux-f2fs-devel wrote:
> From: Jaegeuk Kim <[email protected]>
>
> This adds a fragread command in f2fs_io, which is able to measure the
> read performance on fragmented data buffer.
>
> Signed-off-by: Jaegeuk Kim <[email protected]>
> ---
> tools/f2fs_io/f2fs_io.c | 110 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 110 insertions(+)
>
> diff --git a/tools/f2fs_io/f2fs_io.c b/tools/f2fs_io/f2fs_io.c
> index b72c26648f56..8431262575e0 100644
> --- a/tools/f2fs_io/f2fs_io.c
> +++ b/tools/f2fs_io/f2fs_io.c
> @@ -1018,6 +1018,115 @@ static void do_read(int argc, char **argv, const
> struct cmd_desc *cmd)
> exit(0);
> }
>
> +#define fragread_desc "read data with a fragmented buffer from file"
> +#define fragread_help \
> +"f2fs_io fragread [chunk_size in 4kb] [offset in chunk_size] [count]
> [advice] [file_path]\n\n" \
> +"Read data in file_path and print nbytes\n" \
> +"advice can be\n" \
> +" 1 : set sequential|willneed\n" \
> +" 0 : none\n" \
> +
> +#ifndef PAGE_SIZE
> +#define PAGE_SIZE sysconf(_SC_PAGESIZE)
> +#endif
> +#define ALLOC_SIZE (2 * 1024 * 1024 - 4 * 1024) // 2MB - 4KB
> +
> +static void do_fragread(int argc, char **argv, const struct cmd_desc *cmd)
> +{
> + u64 buf_size = 0, ret = 0, read_cnt = 0;
> + u64 offset;
> + char *buf = NULL;
> + uintptr_t idx, ptr;
> + unsigned bs, count, i;
> + u64 total_time = 0;
> + int flags = 0, alloc_count = 0;
> + void *mem_hole, **mem_holes;
> + int fd, advice;
> +
> + if (argc != 6) {
> + fputs("Excess arguments\n\n", stderr);
> + fputs(cmd->cmd_help, stderr);
> + exit(1);
> + }
> +
> + bs = atoi(argv[1]);
> + if (bs > 256 * 1024)
> + die("Too big chunk size - limit: 1GB");
> + buf_size = bs * F2FS_DEFAULT_BLKSIZE;
> +
> + offset = atoi(argv[2]) * buf_size;
> + count = atoi(argv[3]);
> + advice = atoi(argv[4]);
> + mem_holes = xmalloc(sizeof(void *) * (buf_size / PAGE_SIZE));
> +
> + /* 1. Allocate the buffer using mmap. */
> + buf = mmap(NULL, buf_size, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +
> + /* 2. Loop and touch each page. */
> + for (idx = (uintptr_t)buf; idx < (uintptr_t)buf + buf_size;
> + idx += PAGE_SIZE)
> + {
> + /* Touch the current page. */
> + volatile char *page = (volatile char *)idx;
> + *page;
> +
> + /* 3. Allocate (2M - 4K) memory using mmap and touch all of it.
> */
> + mem_hole = mmap(NULL, ALLOC_SIZE, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + if (mem_hole == MAP_FAILED)
> + die_errno("map failed");
> +
> + /* Store the allocated memory pointer. */
> + mem_holes[alloc_count++] = mem_hole;
Do we need to call mlock to hold allocated cache in the memory, if
administrator enables swap, memory fragment will be gone once anonymous
pages are swapped to device?
Thanks,
> +
> + /* Touch all allocated memory. */
> + for (ptr = (uintptr_t)mem_hole;
> + ptr < (uintptr_t)mem_hole + ALLOC_SIZE;
> + ptr += PAGE_SIZE) {
> + volatile char *alloc_page = (volatile char *)ptr;
> + *alloc_page;
> + }
> + }
> + printf("Touched allocated memory: count = %u\n", alloc_count);
> + printf(" - allocated memory: = ");
> + for (idx = 0; idx < 5; idx++)
> + printf(" %p", mem_holes[idx]);
> + printf("\n");
> +
> + fd = xopen(argv[5], O_RDONLY | flags, 0);
> +
> + if (advice) {
> + if (posix_fadvise(fd, 0, F2FS_DEFAULT_BLKSIZE,
> + POSIX_FADV_SEQUENTIAL) != 0)
> + die_errno("fadvise failed");
> + if (posix_fadvise(fd, 0, F2FS_DEFAULT_BLKSIZE,
> + POSIX_FADV_WILLNEED) != 0)
> + die_errno("fadvise failed");
> + printf("fadvise SEQUENTIAL|WILLNEED to a file: %s\n", argv[5]);
> + }
> +
> + total_time = get_current_us();
> +
> + for (i = 0; i < count; i++) {
> + ret = pread(fd, buf, buf_size, offset + buf_size * i);
> + if (ret != buf_size) {
> + printf("pread expected: %"PRIu64", readed: %"PRIu64"\n",
> + buf_size, ret);
> + if (ret > 0)
> + read_cnt += ret;
> + break;
> + }
> +
> + read_cnt += ret;
> + }
> + printf("Fragmented_Read %"PRIu64" bytes total_time = %"PRIu64" us, BW =
> %.Lf MB/s\n",
> + read_cnt, get_current_us() - total_time,
> + ((long double)read_cnt / (get_current_us() - total_time)));
> + printf("\n");
> + exit(0);
> +}
> +
> #define randread_desc "random read data from file"
> #define randread_help \
> "f2fs_io randread [chunk_size in 4kb] [count] [IO] [advise] [file_path]\n\n"
> \
> @@ -2002,6 +2111,7 @@ const struct cmd_desc cmd_list[] = {
> CMD(write_advice),
> CMD(read),
> CMD(randread),
> + CMD(fragread),
> CMD(fiemap),
> CMD(gc_urgent),
> CMD(defrag_file),
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