[BLOCK] cfq-iosched: seek and async performance fixes

Detect whether a given process is seeky and if so disable (mostly) the
idle window if it is. We still allow just a little idle time, just enough
to allow that process to submit a new request. That is needed to maintain
fairness across priority groups.

In some cases, we could setup several async queues. This is not optimal
from a performance POV, since we want all async io in one queue to perform
good sorting on it. It also impacted sync queues, as async io got too much
slice time.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index ed0ffa673568..d0cac8b58de7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -63,11 +63,17 @@ struct cfq_io_context {
         struct io_context *ioc;
 
         unsigned long last_end_request;
-        unsigned long last_queue;
+        sector_t last_request_pos;
+        unsigned long last_queue;
+
         unsigned long ttime_total;
         unsigned long ttime_samples;
         unsigned long ttime_mean;
 
+        unsigned int seek_samples;
+        u64 seek_total;
+        sector_t seek_mean;
+
         struct list_head queue_list;
 
         void (*dtor)(struct io_context *); /* destructor */