direct-io: inline the complete submission path
Add inlines to all the submission path functions. While this increases
code size it also gives gcc a lot of optimization opportunities
in this critical hotpath.
In particular -- together with some other changes -- this
allows gcc to get rid of the unnecessary clearing of
sdio at the beginning and optimize the messy parameter passing.
Any non inlining of a function which takes a sdio parameter
would break this optimization because they cannot be done if the
address of a structure is taken.
Note that benefits are only seen with CONFIG_OPTIMIZE_INLINING
and CONFIG_CC_OPTIMIZE_FOR_SIZE both set to off.
This gives about 2.2% improvement on a large database benchmark
with a high IOPS rate.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/direct-io.c b/fs/direct-io.c
index edf3174..6d42582 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -199,7 +199,7 @@
/*
* Go grab and pin some userspace pages. Typically we'll get 64 at a time.
*/
-static int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
+static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
{
int ret;
int nr_pages;
@@ -245,7 +245,8 @@
* decent number of pages, less frequently. To provide nicer use of the
* L1 cache.
*/
-static struct page *dio_get_page(struct dio *dio, struct dio_submit *sdio)
+static inline struct page *dio_get_page(struct dio *dio,
+ struct dio_submit *sdio)
{
if (dio_pages_present(sdio) == 0) {
int ret;
@@ -376,7 +377,7 @@
}
EXPORT_SYMBOL_GPL(dio_end_io);
-static void
+static inline void
dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
struct block_device *bdev,
sector_t first_sector, int nr_vecs)
@@ -407,7 +408,7 @@
*
* bios hold a dio reference between submit_bio and ->end_io.
*/
-static void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
+static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
{
struct bio *bio = sdio->bio;
unsigned long flags;
@@ -435,7 +436,7 @@
/*
* Release any resources in case of a failure
*/
-static void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
+static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
{
while (dio_pages_present(sdio))
page_cache_release(dio_get_page(dio, sdio));
@@ -528,7 +529,7 @@
*
* This also helps to limit the peak amount of pinned userspace memory.
*/
-static int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
+static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
{
int ret = 0;
@@ -631,8 +632,8 @@
/*
* There is no bio. Make one now.
*/
-static int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
- sector_t start_sector, struct buffer_head *map_bh)
+static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
+ sector_t start_sector, struct buffer_head *map_bh)
{
sector_t sector;
int ret, nr_pages;
@@ -657,7 +658,7 @@
*
* Return zero on success. Non-zero means the caller needs to start a new BIO.
*/
-static int dio_bio_add_page(struct dio_submit *sdio)
+static inline int dio_bio_add_page(struct dio_submit *sdio)
{
int ret;
@@ -689,8 +690,8 @@
* The caller of this function is responsible for removing cur_page from the
* dio, and for dropping the refcount which came from that presence.
*/
-static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
- struct buffer_head *map_bh)
+static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
+ struct buffer_head *map_bh)
{
int ret = 0;
@@ -759,7 +760,7 @@
* If that doesn't work out then we put the old page into the bio and add this
* page to the dio instead.
*/
-static int
+static inline int
submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
unsigned offset, unsigned len, sector_t blocknr,
struct buffer_head *map_bh)
@@ -842,8 +843,8 @@
* `end' is zero if we're doing the start of the IO, 1 at the end of the
* IO.
*/
-static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end,
- struct buffer_head *map_bh)
+static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
+ int end, struct buffer_head *map_bh)
{
unsigned dio_blocks_per_fs_block;
unsigned this_chunk_blocks; /* In dio_blocks */
@@ -1042,7 +1043,7 @@
return ret;
}
-static ssize_t
+static inline ssize_t
direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
const struct iovec *iov, loff_t offset, unsigned long nr_segs,
unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
@@ -1216,6 +1217,11 @@
* expected that filesystem provide exclusion between new direct I/O
* and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
* but other filesystems need to take care of this on their own.
+ *
+ * NOTE: if you pass "sdio" to anything by pointer make sure that function
+ * is always inlined. Otherwise gcc is unable to split the structure into
+ * individual fields and will generate much worse code. This is important
+ * for the whole file.
*/
ssize_t
__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,