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

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