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authorJens Axboe <jens.axboe@oracle.com>2008-12-23 12:42:54 +0100
committerJens Axboe <jens.axboe@oracle.com>2008-12-29 08:29:50 +0100
commit392ddc32982a5c661dd90dd49a3cb37f1c68b782 (patch)
tree614b8e857a70ce479bcbbf24af66a56b7723efc8 /include/linux/bio.h
parentbb799ca0202a360fa74d5f17039b9100caebdde7 (diff)
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>
Diffstat (limited to 'include/linux/bio.h')
-rw-r--r--include/linux/bio.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 4b80d3537f9..18462c5b8ff 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -102,6 +102,13 @@ struct bio {
#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 @@ static inline void *bio_data(struct bio *bio)
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
*/