bio: optimize initialization of a bio

The memset() used is measurably slower in targeted benchmarks, wasting
about 1% of the total runtime, or 50% of the (later) hot path cached
bio alloc. Get rid of it and fill in the bio manually.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index 1fab762..6fa5c65 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -246,12 +246,40 @@ static void bio_free(struct bio *bio)
 void bio_init(struct bio *bio, struct bio_vec *table,
              unsigned short max_vecs)
 {
-       memset(bio, 0, sizeof(*bio));
+       bio->bi_next = NULL;
+       bio->bi_bdev = NULL;
+       bio->bi_opf = 0;
+       bio->bi_flags = 0;
+       bio->bi_ioprio = 0;
+       bio->bi_write_hint = 0;
+       bio->bi_status = 0;
+       bio->bi_iter.bi_sector = 0;
+       bio->bi_iter.bi_size = 0;
+       bio->bi_iter.bi_idx = 0;
+       bio->bi_iter.bi_bvec_done = 0;
+       bio->bi_end_io = NULL;
+       bio->bi_private = NULL;
+#ifdef CONFIG_BLK_CGROUP
+       bio->bi_blkg = NULL;
+       bio->bi_issue.value = 0;
+#ifdef CONFIG_BLK_CGROUP_IOCOST
+       bio->bi_iocost_cost = 0;
+#endif
+#endif
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+       bio->bi_crypt_context = NULL;
+#endif
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+       bio->bi_integrity = NULL;
+#endif
+       bio->bi_vcnt = 0;
+
        atomic_set(&bio->__bi_remaining, 1);
        atomic_set(&bio->__bi_cnt, 1);
 
-       bio->bi_io_vec = table;
        bio->bi_max_vecs = max_vecs;
+       bio->bi_io_vec = table;
+       bio->bi_pool = NULL;
 }
 EXPORT_SYMBOL(bio_init);