diff options
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/pktcdvd.c | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c index bc56770bcc90..7f3d78de265c 100644 --- a/drivers/block/pktcdvd.c +++ b/drivers/block/pktcdvd.c @@ -467,14 +467,12 @@ static int pkt_set_speed(struct pktcdvd_device *pd, unsigned write_speed, unsign * Queue a bio for processing by the low-level CD device. Must be called * from process context. */ -static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio, int high_prio_read) +static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio) { spin_lock(&pd->iosched.lock); if (bio_data_dir(bio) == READ) { pkt_add_list_last(bio, &pd->iosched.read_queue, &pd->iosched.read_queue_tail); - if (high_prio_read) - pd->iosched.high_prio_read = 1; } else { pkt_add_list_last(bio, &pd->iosched.write_queue, &pd->iosched.write_queue_tail); @@ -490,15 +488,16 @@ static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio, int high_p * requirements for CDRW drives: * - A cache flush command must be inserted before a read request if the * previous request was a write. - * - Switching between reading and writing is slow, so don't it more often + * - Switching between reading and writing is slow, so don't do it more often * than necessary. + * - Optimize for throughput at the expense of latency. This means that streaming + * writes will never be interrupted by a read, but if the drive has to seek + * before the next write, switch to reading instead if there are any pending + * read requests. * - Set the read speed according to current usage pattern. When only reading * from the device, it's best to use the highest possible read speed, but * when switching often between reading and writing, it's better to have the * same read and write speeds. - * - Reads originating from user space should have higher priority than reads - * originating from pkt_gather_data, because some process is usually waiting - * on reads of the first kind. */ static void pkt_iosched_process_queue(struct pktcdvd_device *pd) { @@ -512,21 +511,24 @@ static void pkt_iosched_process_queue(struct pktcdvd_device *pd) for (;;) { struct bio *bio; - int reads_queued, writes_queued, high_prio_read; + int reads_queued, writes_queued; spin_lock(&pd->iosched.lock); reads_queued = (pd->iosched.read_queue != NULL); writes_queued = (pd->iosched.write_queue != NULL); - if (!reads_queued) - pd->iosched.high_prio_read = 0; - high_prio_read = pd->iosched.high_prio_read; spin_unlock(&pd->iosched.lock); if (!reads_queued && !writes_queued) break; if (pd->iosched.writing) { - if (high_prio_read || (!writes_queued && reads_queued)) { + int need_write_seek = 1; + spin_lock(&pd->iosched.lock); + bio = pd->iosched.write_queue; + spin_unlock(&pd->iosched.lock); + if (bio && (bio->bi_sector == pd->iosched.last_write)) + need_write_seek = 0; + if (need_write_seek && reads_queued) { if (atomic_read(&pd->cdrw.pending_bios) > 0) { VPRINTK("pktcdvd: write, waiting\n"); break; @@ -559,8 +561,10 @@ static void pkt_iosched_process_queue(struct pktcdvd_device *pd) if (bio_data_dir(bio) == READ) pd->iosched.successive_reads += bio->bi_size >> 10; - else + else { pd->iosched.successive_reads = 0; + pd->iosched.last_write = bio->bi_sector + bio_sectors(bio); + } if (pd->iosched.successive_reads >= HI_SPEED_SWITCH) { if (pd->read_speed == pd->write_speed) { pd->read_speed = MAX_SPEED; @@ -765,7 +769,7 @@ static void pkt_gather_data(struct pktcdvd_device *pd, struct packet_data *pkt) atomic_inc(&pkt->io_wait); bio->bi_rw = READ; - pkt_queue_bio(pd, bio, 0); + pkt_queue_bio(pd, bio); frames_read++; } @@ -1062,7 +1066,7 @@ static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt) atomic_set(&pkt->io_wait, 1); pkt->w_bio->bi_rw = WRITE; - pkt_queue_bio(pd, pkt->w_bio, 0); + pkt_queue_bio(pd, pkt->w_bio); } static void pkt_finish_packet(struct packet_data *pkt, int uptodate) @@ -2120,7 +2124,7 @@ static int pkt_make_request(request_queue_t *q, struct bio *bio) cloned_bio->bi_private = psd; cloned_bio->bi_end_io = pkt_end_io_read_cloned; pd->stats.secs_r += bio->bi_size >> 9; - pkt_queue_bio(pd, cloned_bio, 1); + pkt_queue_bio(pd, cloned_bio); return 0; } |