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Subject[085/107] cfq: calculate the seek_mean per cfq_queue not per cfq_io_context
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Moyer <jmoyer@redhat.com>

commit b2c18e1e08a5a9663094d57bb4be2f02226ee61c upstream.

async cfq_queue's are already shared between processes within the same
priority, and forthcoming patches will change the mapping of cic to sync
cfq_queue from 1:1 to 1:N. So, calculate the seekiness of a process
based on the cfq_queue instead of the cfq_io_context.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
block/cfq-iosched.c | 68 ++++++++++++++++++++++------------------------
include/linux/iocontext.h | 5 ---
2 files changed, 33 insertions(+), 40 deletions(-)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -112,6 +112,11 @@ 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;
};

@@ -967,16 +972,16 @@ static inline sector_t cfq_dist_from_las
return cfqd->last_position - blk_rq_pos(rq);
}

-#define CIC_SEEK_THR 8 * 1024
-#define CIC_SEEKY(cic) ((cic)->seek_mean > CIC_SEEK_THR)
+#define CFQQ_SEEK_THR 8 * 1024
+#define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)

-static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
+static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+ struct request *rq)
{
- struct cfq_io_context *cic = cfqd->active_cic;
- sector_t sdist = cic->seek_mean;
+ sector_t sdist = cfqq->seek_mean;

- if (!sample_valid(cic->seek_samples))
- sdist = CIC_SEEK_THR;
+ if (!sample_valid(cfqq->seek_samples))
+ sdist = CFQQ_SEEK_THR;

return cfq_dist_from_last(cfqd, rq) <= sdist;
}
@@ -1005,7 +1010,7 @@ static struct cfq_queue *cfqq_close(stru
* will contain the closest sector.
*/
__cfqq = rb_entry(parent, struct cfq_queue, p_node);
- if (cfq_rq_close(cfqd, __cfqq->next_rq))
+ if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
return __cfqq;

if (blk_rq_pos(__cfqq->next_rq) < sector)
@@ -1016,7 +1021,7 @@ static struct cfq_queue *cfqq_close(stru
return NULL;

__cfqq = rb_entry(node, struct cfq_queue, p_node);
- if (cfq_rq_close(cfqd, __cfqq->next_rq))
+ if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
return __cfqq;

return NULL;
@@ -1039,13 +1044,6 @@ static struct cfq_queue *cfq_close_coope
struct cfq_queue *cfqq;

/*
- * A valid cfq_io_context is necessary to compare requests against
- * the seek_mean of the current cfqq.
- */
- if (!cfqd->active_cic)
- return NULL;
-
- /*
* We should notice if some of the queues are cooperating, eg
* working closely on the same area of the disk. In that case,
* we can group them together and don't waste time idling.
@@ -1115,7 +1113,7 @@ static void cfq_arm_slice_timer(struct c
* seeks. so allow a little bit of time for him to submit a new rq
*/
sl = cfqd->cfq_slice_idle;
- if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
+ if (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq))
sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));

mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
@@ -1958,33 +1956,33 @@ cfq_update_io_thinktime(struct cfq_data
}

static void
-cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
+cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *rq)
{
sector_t sdist;
u64 total;

- if (!cic->last_request_pos)
+ if (!cfqq->last_request_pos)
sdist = 0;
- else if (cic->last_request_pos < blk_rq_pos(rq))
- sdist = blk_rq_pos(rq) - cic->last_request_pos;
+ else if (cfqq->last_request_pos < blk_rq_pos(rq))
+ sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
else
- sdist = cic->last_request_pos - blk_rq_pos(rq);
+ 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 (cic->seek_samples <= 60) /* second&third seek */
- sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
+ if (cfqq->seek_samples <= 60) /* second&third seek */
+ sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
else
- sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
+ sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);

- cic->seek_samples = (7*cic->seek_samples + 256) / 8;
- cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
- total = cic->seek_total + (cic->seek_samples/2);
- do_div(total, cic->seek_samples);
- cic->seek_mean = (sector_t)total;
+ 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;
}

/*
@@ -2006,11 +2004,11 @@ cfq_update_idle_window(struct cfq_data *
enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);

if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
- (!cfqd->cfq_latency && cfqd->hw_tag && CIC_SEEKY(cic)))
+ (!cfqd->cfq_latency && cfqd->hw_tag && CFQQ_SEEKY(cfqq)))
enable_idle = 0;
else if (sample_valid(cic->ttime_samples)) {
unsigned int slice_idle = cfqd->cfq_slice_idle;
- if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
+ if (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq))
slice_idle = msecs_to_jiffies(CFQ_MIN_TT);
if (cic->ttime_mean > slice_idle)
enable_idle = 0;
@@ -2077,7 +2075,7 @@ cfq_should_preempt(struct cfq_data *cfqd
* if this request is as-good as one we would expect from the
* current cfqq, let it preempt
*/
- if (cfq_rq_close(cfqd, rq) && (!cfq_cfqq_coop(new_cfqq) ||
+ if (cfq_rq_close(cfqd, cfqq, rq) && (!cfq_cfqq_coop(new_cfqq) ||
cfqd->busy_queues == 1)) {
/*
* Mark new queue coop_preempt, so its coop flag will not be
@@ -2127,10 +2125,10 @@ cfq_rq_enqueued(struct cfq_data *cfqd, s
cfqq->meta_pending++;

cfq_update_io_thinktime(cfqd, cic);
- cfq_update_io_seektime(cfqd, cic, rq);
+ cfq_update_io_seektime(cfqd, cfqq, rq);
cfq_update_idle_window(cfqd, cfqq, cic);

- cic->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
+ cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);

if (cfqq == cfqd->active_queue) {
/*
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -40,16 +40,11 @@ struct cfq_io_context {
struct io_context *ioc;

unsigned long last_end_request;
- sector_t last_request_pos;

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;
struct hlist_node cic_list;




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