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authorCorrado Zoccolo <czoccolo@gmail.com>2010-02-27 19:45:40 +0100
committerJens Axboe <jens.axboe@oracle.com>2010-02-28 19:41:25 +0100
commit41647e7a91338dba21773a16af7474ef95e0929e (patch)
tree9520ffbb853af141af5b802fa00f5a2e4ed783bd /block
parent3dde36ddea3e07dd025c4c1ba47edec91606fec0 (diff)
downloadlinux-2.6.34-ux500-41647e7a91338dba21773a16af7474ef95e0929e.tar.gz
cfq-iosched: rethink seeky detection for SSDs
CFQ currently applies the same logic of detecting seeky queues and grouping them together for rotational disks as well as SSDs. For SSDs, the time to complete a request doesn't depend on the request location, but only on the size. This patch therefore changes the criterion to group queues by request size in case of SSDs, in order to achieve better fairness. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/cfq-iosched.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3fd8afc2174..423aee3fd19 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -47,6 +47,7 @@ static const int cfq_hist_divisor = 4;
#define CFQ_SERVICE_SHIFT 12
#define CFQQ_SEEK_THR (sector_t)(8 * 100)
+#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
#define RQ_CIC(rq) \
@@ -2965,6 +2966,7 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *rq)
{
sector_t sdist = 0;
+ sector_t n_sec = blk_rq_sectors(rq);
if (cfqq->last_request_pos) {
if (cfqq->last_request_pos < blk_rq_pos(rq))
sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
@@ -2973,7 +2975,10 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
}
cfqq->seek_history <<= 1;
- cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
+ if (blk_queue_nonrot(cfqd->queue))
+ cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
+ else
+ cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
}
/*