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authorAlan D. Brunelle2010-01-29 02:04:08 -0600
committerJens Axboe2010-01-29 02:04:08 -0600
commit488991e28e55b4fbca8067edf0259f69d1a6f92c (patch)
treefea5e0aca42e338137cc050e66aaeb5f539e3d21 /block/blk-sysfs.c
parent47483e25205f1f8d79784f0f7c733941bc080ec0 (diff)
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block: Added in stricter no merge semantics for block I/O
Updated 'nomerges' tunable to accept a value of '2' - indicating that _no_ merges at all are to be attempted (not even the simple one-hit cache). The following table illustrates the additional benefit - 5 minute runs of a random I/O load were applied to a dozen devices on a 16-way x86_64 system. nomerges Throughput %System Improvement (tput / %sys) -------- ------------ ----------- ------------------------- 0 12.45 MB/sec 0.669365609 1 12.50 MB/sec 0.641519199 0.40% / 2.71% 2 12.52 MB/sec 0.639849750 0.56% / 2.96% Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/blk-sysfs.c')
-rw-r--r--block/blk-sysfs.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8606c9543fd..e85442415db 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -189,7 +189,8 @@ static ssize_t queue_nonrot_store(struct request_queue *q, const char *page,
189 189
190static ssize_t queue_nomerges_show(struct request_queue *q, char *page) 190static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
191{ 191{
192 return queue_var_show(blk_queue_nomerges(q), page); 192 return queue_var_show((blk_queue_nomerges(q) << 1) |
193 blk_queue_noxmerges(q), page);
193} 194}
194 195
195static ssize_t queue_nomerges_store(struct request_queue *q, const char *page, 196static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
@@ -199,10 +200,12 @@ static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
199 ssize_t ret = queue_var_store(&nm, page, count); 200 ssize_t ret = queue_var_store(&nm, page, count);
200 201
201 spin_lock_irq(q->queue_lock); 202 spin_lock_irq(q->queue_lock);
202 if (nm) 203 queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
204 queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
205 if (nm == 2)
203 queue_flag_set(QUEUE_FLAG_NOMERGES, q); 206 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
204 else 207 else if (nm)
205 queue_flag_clear(QUEUE_FLAG_NOMERGES, q); 208 queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
206 spin_unlock_irq(q->queue_lock); 209 spin_unlock_irq(q->queue_lock);
207 210
208 return ret; 211 return ret;