[Devel] Re: [PATCH] cfq: get rid of cfqq hash

[Jens Axboe]

On Wed, Apr 25 2007, Jens Axboe wrote:
> On Tue, Apr 24 2007, Vasily Tarasov wrote:
> > @@ -1806,7 +1765,11 @@ static int cfq_may_queue(request_queue_t
> >  	 * so just lookup a possibly existing queue, or return 'may queue'
> >  	 * if that fails
> >  	 */
> > -	cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
> > +	cic = cfq_get_io_context_noalloc(cfqd, tsk);
> > +	if (!cic)
> > +		return ELV_MQUEUE_MAY; 
> > +
> > +	cfqq = cic->cfqq[rw & REQ_RW_SYNC];
> >  	if (cfqq) {
> >  		cfq_init_prio_data(cfqq);
> >  		cfq_prio_boost(cfqq);
> 
> Ahem, how well did you test this patch?

Incremental update to get things working below.

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ed1ce43..17e4660 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -202,6 +202,18 @@ static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
 static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
 						struct io_context *);
 
+static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
+					    int is_sync)
+{
+	return cic->cfqq[!!is_sync];
+}
+
+static inline void cic_set_cfqq(struct cfq_io_context *cic,
+				struct cfq_queue *cfqq, int is_sync)
+{
+	cic->cfqq[!!is_sync] = cfqq;
+}
+
 /*
  * scheduler run of queue, if there are requests pending and no one in the
  * driver that will restart queueing
@@ -582,7 +594,7 @@ cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 	if (!cic)
 		return NULL;
 
-	cfqq =  cic->cfqq[bio_sync(bio)];
+	cfqq =  cic_to_cfqq(cic, bio_sync(bio));
 	if (cfqq) {
 		sector_t sector = bio->bi_sector + bio_sectors(bio);
 
@@ -693,7 +705,7 @@ static int cfq_allow_merge(request_queue_t *q, struct request *rq,
 	if (!cic)
 		return 0;
 
-	cfqq = cic->cfqq[bio_sync(bio)];
+	cfqq = cic_to_cfqq(cic, bio_sync(bio));
 	if (cfqq == RQ_CFQQ(rq))
 		return 1;
 
@@ -1330,7 +1342,7 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
 retry:
 	cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
 	/* cic always exists here */
-	cfqq = cic->cfqq[is_sync];
+	cfqq = cic_to_cfqq(cic, is_sync);
 
 	if (!cfqq) {
 		if (new_cfqq) {
@@ -1821,7 +1833,7 @@ static int cfq_may_queue(request_queue_t *q, int rw)
 	if (!cic)
 		return ELV_MQUEUE_MAY;
 
-	cfqq = cic->cfqq[rw & REQ_RW_SYNC];
+	cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
 	if (cfqq) {
 		cfq_init_prio_data(cfqq);
 		cfq_prio_boost(cfqq);
@@ -1877,15 +1889,15 @@ cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
 	if (!cic)
 		goto queue_fail;
 
-	if (!cic->cfqq[is_sync]) {
+	cfqq = cic_to_cfqq(cic, is_sync);
+	if (!cfqq) {
 		cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
 
 		if (!cfqq)
 			goto queue_fail;
 
-		cic->cfqq[is_sync] = cfqq;
-	} else
-		cfqq = cic->cfqq[is_sync];
+		cic_set_cfqq(cic, cfqq, is_sync);
+	}
 
 	cfqq->allocated[rw]++;
 	cfq_clear_cfqq_must_alloc(cfqq);

-- 
Jens Axboe