cfq-iosched: rethink seeky detection for SSDs

[pandora-kernel.git] / block / cfq-iosched.c

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 023f4e6..423aee3 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -46,8 +46,9 @@ static const int cfq_hist_divisor = 4;
 #define CFQ_HW_QUEUE_MIN       (5)
 #define CFQ_SERVICE_SHIFT       12
 
-#define CFQQ_SEEK_THR          8 * 1024
-#define CFQQ_SEEKY(cfqq)       ((cfqq)->seek_mean > CFQQ_SEEK_THR)
+#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)             \
        ((struct cfq_io_context *) (rq)->elevator_private)
@@ -115,11 +116,11 @@ struct cfq_queue {
        /* time when queue got scheduled in to dispatch first request. */
        unsigned long dispatch_start;
        unsigned int allocated_slice;
+       unsigned int slice_dispatch;
        /* time when first request from queue completed and slice started. */
        unsigned long slice_start;
        unsigned long slice_end;
        long slice_resid;
-       unsigned int slice_dispatch;
 
        /* pending metadata requests */
        int meta_pending;
@@ -130,13 +131,11 @@ struct cfq_queue {
        unsigned short ioprio, org_ioprio;
        unsigned short ioprio_class, org_ioprio_class;
 
-       unsigned int seek_samples;
-       u64 seek_total;
-       sector_t seek_mean;
-       sector_t last_request_pos;
-
        pid_t pid;
 
+       u32 seek_history;
+       sector_t last_request_pos;
+
        struct cfq_rb_root *service_tree;
        struct cfq_queue *new_cfqq;
        struct cfq_group *cfqg;
@@ -951,10 +950,6 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
        struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
        unsigned int major, minor;
 
-       /* Do we need to take this reference */
-       if (!blkiocg_css_tryget(blkcg))
-               return NULL;;
-
        cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
        if (cfqg || !create)
                goto done;
@@ -985,7 +980,6 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
        hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
 
 done:
-       blkiocg_css_put(blkcg);
        return cfqg;
 }
 
@@ -1673,16 +1667,7 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                               struct request *rq, bool for_preempt)
 {
-       sector_t sdist = cfqq->seek_mean;
-
-       if (!sample_valid(cfqq->seek_samples))
-               sdist = CFQQ_SEEK_THR;
-
-       /* if seek_mean is big, using it as close criteria is meaningless */
-       if (sdist > CFQQ_SEEK_THR && !for_preempt)
-               sdist = CFQQ_SEEK_THR;
-
-       return cfq_dist_from_last(cfqd, rq) <= sdist;
+       return cfq_dist_from_last(cfqd, rq) <= CFQQ_SEEK_THR;
 }
 
 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
@@ -2980,30 +2965,20 @@ static void
 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                       struct request *rq)
 {
-       sector_t sdist;
-       u64 total;
-
-       if (!cfqq->last_request_pos)
-               sdist = 0;
-       else if (cfqq->last_request_pos < blk_rq_pos(rq))
-               sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
-       else
-               sdist = cfqq->last_request_pos - blk_rq_pos(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;
+               else
+                       sdist = cfqq->last_request_pos - blk_rq_pos(rq);
+       }
 
-       /*
-        * Don't allow the seek distance to get too large from the
-        * odd fragment, pagein, etc
-        */
-       if (cfqq->seek_samples <= 60) /* second&third seek */
-               sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
+       cfqq->seek_history <<= 1;
+       if (blk_queue_nonrot(cfqd->queue))
+               cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
        else
-               sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
-
-       cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
-       cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
-       total = cfqq->seek_total + (cfqq->seek_samples/2);
-       do_div(total, cfqq->seek_samples);
-       cfqq->seek_mean = (sector_t)total;
+               cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
 }
 
 /*
@@ -3028,8 +3003,7 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                cfq_mark_cfqq_deep(cfqq);
 
        if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
-           (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)
-            && CFQQ_SEEKY(cfqq)))
+           (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
                enable_idle = 0;
        else if (sample_valid(cic->ttime_samples)) {
                if (cic->ttime_mean > cfqd->cfq_slice_idle)