dedupe: improve 100% dedupe case

We don't need an on-stack state, just juggle the buf_state and
buf_state_prev appropriately.

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

diff --git a/io_u.c b/io_u.c
index 69ca6fe06ff8abfa30be5694a24bbca810c3e5f8..d00e6e3fe44a593033670cd5f226fa07395a5698 100644 (file)
--- a/io_u.c
+++ b/io_u.c
@@ -1889,8 +1889,7 @@ void io_u_queued(struct thread_data *td, struct io_u *io_u)
 /*
  * See if we should reuse the last seed, if dedupe is enabled
  */
-static struct frand_state *get_buf_state(struct thread_data *td,
-                                        struct frand_state *save)
+static struct frand_state *get_buf_state(struct thread_data *td)
 {
        unsigned int v;
        unsigned long r;
@@ -1898,8 +1897,8 @@ static struct frand_state *get_buf_state(struct thread_data *td,
        if (!td->o.dedupe_percentage)
                return &td->buf_state;
        else if (td->o.dedupe_percentage == 100) {
-               frand_copy(save, &td->buf_state_prev);
-               return &td->buf_state_prev;
+               frand_copy(&td->buf_state_prev, &td->buf_state);
+               return &td->buf_state;
        }
 
        r = __rand(&td->dedupe_state);
@@ -1911,20 +1910,18 @@ static struct frand_state *get_buf_state(struct thread_data *td,
        return &td->buf_state;
 }
 
-static void save_buf_state(struct thread_data *td, struct frand_state *rs,
-                          struct frand_state *save)
+static void save_buf_state(struct thread_data *td, struct frand_state *rs)
 {
-       if (rs == &td->buf_state)
+       if (td->o.dedupe_percentage == 100)
+               frand_copy(rs, &td->buf_state_prev);
+       else if (rs == &td->buf_state)
                frand_copy(&td->buf_state_prev, rs);
-       else if (rs == &td->buf_state_prev && td->o.dedupe_percentage == 100)
-               frand_copy(rs, save);
 }
 
 void fill_io_buffer(struct thread_data *td, void *buf, unsigned int min_write,
                    unsigned int max_bs)
 {
        struct thread_options *o = &td->o;
-       struct frand_state save = { 0, };
 
        if (o->compress_percentage || o->dedupe_percentage) {
                unsigned int perc = td->o.compress_percentage;
@@ -1932,7 +1929,7 @@ void fill_io_buffer(struct thread_data *td, void *buf, unsigned int min_write,
                unsigned int left = max_bs;
 
                do {
-                       rs = get_buf_state(td, &save);
+                       rs = get_buf_state(td);
 
                        min_write = min(min_write, left);
 
@@ -1951,14 +1948,14 @@ void fill_io_buffer(struct thread_data *td, void *buf, unsigned int min_write,
 
                        buf += min_write;
                        left -= min_write;
-                       save_buf_state(td, rs, &save);
+                       save_buf_state(td, rs);
                } while (left);
        } else if (o->buffer_pattern_bytes)
                fill_buffer_pattern(td, buf, max_bs);
        else if (o->zero_buffers)
                memset(buf, 0, max_bs);
        else
-               fill_random_buf(get_buf_state(td, NULL), buf, max_bs);
+               fill_random_buf(get_buf_state(td), buf, max_bs);
 }
 
 /*