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block: Add flag for telling the IO schedulers NOT to anticipate more IO

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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>
This commit is contained in:
Jens Axboe
2009-04-06 14:48:07 +02:00
committed by Linus Torvalds
parent 644b2d99b7
commit aeb6fafb8f
6 changed files with 25 additions and 14 deletions
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9
include/linux/fs.h
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@@ -95,11 +95,12 @@ struct inodes_stat_t {
#define SWRITE 3 /* for ll_rw_block() - wait for buffer lock */
#define READ_SYNC (READ | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG))
#define READ_META (READ | (1 << BIO_RW_META))
#define WRITE_SYNC (WRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG))
#define WRITE_SYNC_PLUG (WRITE | (1 << BIO_RW_SYNCIO))
#define SWRITE_SYNC (SWRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG))
#define WRITE_SYNC_PLUG (WRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_NOIDLE))
#define WRITE_SYNC (WRITE_SYNC_PLUG | (1 << BIO_RW_UNPLUG))
#define WRITE_ODIRECT (WRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG))
#define SWRITE_SYNC_PLUG \
(SWRITE | (1 << BIO_RW_SYNCIO))
(SWRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_NOIDLE))
#define SWRITE_SYNC (SWRITE_SYNC_PLUG | (1 << BIO_RW_UNPLUG))
#define WRITE_BARRIER (WRITE | (1 << BIO_RW_BARRIER))
#define DISCARD_NOBARRIER (1 << BIO_RW_DISCARD)
#define DISCARD_BARRIER ((1 << BIO_RW_DISCARD) | (1 << BIO_RW_BARRIER))