[PATCH] More random map fixes

Several optimizations and fixes:

- Add ->last_free_lookup as a cache for get_next_free_offset(). No point
  in iterating known full blocks.
- Reduce number of random loops to 5 for random map lookups, fallback to
  next free block instead of wasting cpu cycles. Was 50.
- get_next_free_block() needs to take file offset into account.
- Reverse order of retrieving buflen and offset, so we can trim
  and mark properly.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/fio.h b/fio.h
index e42d67bb137d721b92936e1249176c5ceabfee15..b396450e7836da890cd0e21f462654c0c12b7d58 100644 (file)
--- a/fio.h
+++ b/fio.h
@@ -170,6 +170,8 @@ struct fio_file {
        unsigned int num_maps;
 
        unsigned int unlink;
+
+       unsigned int last_free_lookup;
 };
 
 /*

diff --git a/io_u.c b/io_u.c
index 31f75cd6794ed09ecc5a2b2e193ce5f2714f2cf4..34c7e6f44bce50fed649380d391977de9752b32c 100644 (file)
--- a/io_u.c
+++ b/io_u.c
@@ -30,10 +30,13 @@ static void mark_random_map(struct thread_data *td, struct fio_file *f,
        unsigned int min_bs = td->rw_min_bs;
        unsigned long long block;
        unsigned int blocks;
+       unsigned int nr_blocks;
 
        block = io_u->offset / (unsigned long long) min_bs;
        blocks = 0;
-       while (blocks < ((io_u->buflen + min_bs - 1) / min_bs)) {
+       nr_blocks = (io_u->buflen + min_bs - 1) / min_bs;
+
+       while (blocks < nr_blocks) {
                unsigned int idx, bit;
 
                if (!random_map_free(td, f, block))
@@ -61,11 +64,12 @@ static int get_next_free_block(struct thread_data *td, struct fio_file *f,
 {
        int i;
 
-       *b = 0;
-       i = 0;
+       i = f->last_free_lookup;
+       *b = (i * BLOCKS_PER_MAP);
        while ((*b) * td->rw_min_bs < f->real_file_size) {
                if (f->file_map[i] != -1UL) {
                        *b += ffz(f->file_map[i]);
+                       f->last_free_lookup = i;
                        return 0;
                }
 
@@ -82,14 +86,15 @@ static int get_next_free_block(struct thread_data *td, struct fio_file *f,
  * the last io issued.
  */
 static int get_next_offset(struct thread_data *td, struct fio_file *f,
-                          unsigned long long *offset, int ddir)
+                          struct io_u *io_u)
 {
+       const int ddir = io_u->ddir;
        unsigned long long b, rb;
        long r;
 
        if (!td->sequential) {
                unsigned long long max_blocks = f->file_size / td->min_bs[ddir];
-               int loops = 50;
+               int loops = 5;
 
                do {
                        r = os_random_long(&td->random_state);
@@ -103,12 +108,14 @@ static int get_next_offset(struct thread_data *td, struct fio_file *f,
                if (!loops) {
                        if (get_next_free_block(td, f, &b))
                                return 1;
+
+                       b += f->file_offset / td->min_bs[ddir];
                }
        } else
                b = f->last_pos / td->min_bs[ddir];
 
-       *offset = (b * td->min_bs[ddir]) + f->file_offset;
-       if (*offset > f->real_file_size)
+       io_u->offset = (b * td->min_bs[ddir]) + f->file_offset;
+       if (io_u->offset > f->real_file_size)
                return 1;
 
        return 0;
@@ -208,11 +215,19 @@ static int fill_io_u(struct thread_data *td, struct fio_file *f,
        io_u->ddir = get_rw_ddir(td);
 
        /*
-        * No log, let the seq/rand engine retrieve the next position.
+        * No log, let the seq/rand engine retrieve the next buflen and
+        * position.
         */
-       if (!get_next_offset(td, f, &io_u->offset, io_u->ddir)) {
-               io_u->buflen = get_next_buflen(td, io_u->ddir);
-               if (io_u->buflen) {
+       io_u->buflen = get_next_buflen(td, io_u->ddir);
+       if (io_u->buflen) {
+               if (!get_next_offset(td, f, io_u)) {
+                       /*
+                        * mark entry before potentially trimming io_u
+                        */
+                       if (!td->read_iolog && !td->sequential &&
+                           !td->norandommap)
+                               mark_random_map(td, f, io_u);
+
                        /*
                         * If using a write iolog, store this entry.
                         */
@@ -308,9 +323,6 @@ struct io_u *get_io_u(struct thread_data *td, struct fio_file *f)
                        return NULL;
                }
 
-               if (!td->read_iolog && !td->sequential && !td->norandommap)
-                       mark_random_map(td, f, io_u);
-
                f->last_pos += io_u->buflen;
 
                if (td->verify != VERIFY_NONE)