bio: add support for inlining a number of bio_vecs inside the bio
When we go and allocate a bio for IO, we actually do two allocations.
One for the bio itself, and one for the bi_io_vec that holds the
actual pages we are interested in.
This feature inlines a definable amount of io vecs inside the bio
itself, so we eliminate the bio_vec array allocation for IO's up
to a certain size. It defaults to 4 vecs, which is typically 16k
of IO.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 4b80d35..18462c5 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -102,6 +102,13 @@
#endif
bio_destructor_t *bi_destructor; /* destructor */
+
+ /*
+ * We can inline a number of vecs at the end of the bio, to avoid
+ * double allocations for a small number of bio_vecs. This member
+ * MUST obviously be kept at the very end of the bio.
+ */
+ struct bio_vec bi_inline_vecs[0];
};
/*
@@ -213,6 +220,11 @@
return NULL;
}
+static inline int bio_has_allocated_vec(struct bio *bio)
+{
+ return bio->bi_io_vec && bio->bi_io_vec != bio->bi_inline_vecs;
+}
+
/*
* will die
*/