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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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fs/direct-io.c
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@@ -1126,7 +1126,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
int acquire_i_mutex = 0;
if (rw & WRITE)
rw = WRITE_SYNC;
rw = WRITE_ODIRECT;
if (bdev)
bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));