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authorJens Axboe <jens.axboe@oracle.com>2009-04-06 14:48:07 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-06 08:04:54 -0700
commitaeb6fafb8fa53266d70ca7474fcda2bdaf96524a (patch)
treeebe8e0c616a9dbfdfe5184b64d0150ea02d3d1b2 /include/linux/bio.h
parent644b2d99b7a8677a56909a7b1fde31677eba4471 (diff)
block: Add flag for telling the IO schedulers NOT to anticipate more IO
By default, CFQ will anticipate more IO from a given io context if the previously completed IO was sync. This used to be fine, since the only sync IO was reads and O_DIRECT writes. But with more "normal" sync writes being used now, we don't want to anticipate for those. Add a bio/request flag that informs the IO scheduler that this is a sync request that we should not idle for. Introduce WRITE_ODIRECT specifically for O_DIRECT writes, and make sure that the other sync writes set this flag. Signed-off-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/bio.h')
-rw-r--r--include/linux/bio.h19
1 files changed, 11 insertions, 8 deletions
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b05b1d4d17d2..b900d2c67d29 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -145,20 +145,21 @@ struct bio {
* bit 2 -- barrier
* Insert a serialization point in the IO queue, forcing previously
* submitted IO to be completed before this one is issued.
- * bit 3 -- synchronous I/O hint: the block layer will unplug immediately
- * Note that this does NOT indicate that the IO itself is sync, just
- * that the block layer will not postpone issue of this IO by plugging.
- * bit 4 -- metadata request
+ * bit 3 -- synchronous I/O hint.
+ * bit 4 -- Unplug the device immediately after submitting this bio.
+ * bit 5 -- metadata request
* Used for tracing to differentiate metadata and data IO. May also
* get some preferential treatment in the IO scheduler
- * bit 5 -- discard sectors
+ * bit 6 -- discard sectors
* Informs the lower level device that this range of sectors is no longer
* used by the file system and may thus be freed by the device. Used
* for flash based storage.
- * bit 6 -- fail fast device errors
- * bit 7 -- fail fast transport errors
- * bit 8 -- fail fast driver errors
+ * bit 7 -- fail fast device errors
+ * bit 8 -- fail fast transport errors
+ * bit 9 -- fail fast driver errors
* Don't want driver retries for any fast fail whatever the reason.
+ * bit 10 -- Tell the IO scheduler not to wait for more requests after this
+ one has been submitted, even if it is a SYNC request.
*/
#define BIO_RW 0 /* Must match RW in req flags (blkdev.h) */
#define BIO_RW_AHEAD 1 /* Must match FAILFAST in req flags */
@@ -170,6 +171,7 @@ struct bio {
#define BIO_RW_FAILFAST_DEV 7
#define BIO_RW_FAILFAST_TRANSPORT 8
#define BIO_RW_FAILFAST_DRIVER 9
+#define BIO_RW_NOIDLE 10
#define bio_rw_flagged(bio, flag) ((bio)->bi_rw & (1 << (flag)))
@@ -188,6 +190,7 @@ struct bio {
#define bio_rw_ahead(bio) bio_rw_flagged(bio, BIO_RW_AHEAD)
#define bio_rw_meta(bio) bio_rw_flagged(bio, BIO_RW_META)
#define bio_discard(bio) bio_rw_flagged(bio, BIO_RW_DISCARD)
+#define bio_noidle(bio) bio_rw_flagged(bio, BIO_RW_NOIDLE)
/*
* upper 16 bits of bi_rw define the io priority of this bio