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authorPeter Osterlund <petero2@telia.com>2005-06-23 03:10:02 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 12:45:30 -0400
commit46c271bedd2c8444b1d05bc44928beec0c07debc (patch)
tree2e28cad2355b62b01815d1acc10d35a806f10ea0 /drivers/block/pktcdvd.c
parentdfb388bf8a328f206bba33933dd97230f412238b (diff)
[PATCH] Improve CD/DVD packet driver write performance
This patch improves write performance for the CD/DVD packet writing driver. The logic for switching between reading and writing has been changed so that streaming writes are no longer interrupted by read requests. Signed-off-by: Peter Osterlund <petero2@telia.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/block/pktcdvd.c')
-rw-r--r--drivers/block/pktcdvd.c36
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
467 * Queue a bio for processing by the low-level CD device. Must be called 467 * Queue a bio for processing by the low-level CD device. Must be called
468 * from process context. 468 * from process context.
469 */ 469 */
470static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio, int high_prio_read) 470static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio)
471{ 471{
472 spin_lock(&pd->iosched.lock); 472 spin_lock(&pd->iosched.lock);
473 if (bio_data_dir(bio) == READ) { 473 if (bio_data_dir(bio) == READ) {
474 pkt_add_list_last(bio, &pd->iosched.read_queue, 474 pkt_add_list_last(bio, &pd->iosched.read_queue,
475 &pd->iosched.read_queue_tail); 475 &pd->iosched.read_queue_tail);
476 if (high_prio_read)
477 pd->iosched.high_prio_read = 1;
478 } else { 476 } else {
479 pkt_add_list_last(bio, &pd->iosched.write_queue, 477 pkt_add_list_last(bio, &pd->iosched.write_queue,
480 &pd->iosched.write_queue_tail); 478 &pd->iosched.write_queue_tail);
@@ -490,15 +488,16 @@ static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio, int high_p
490 * requirements for CDRW drives: 488 * requirements for CDRW drives:
491 * - A cache flush command must be inserted before a read request if the 489 * - A cache flush command must be inserted before a read request if the
492 * previous request was a write. 490 * previous request was a write.
493 * - Switching between reading and writing is slow, so don't it more often 491 * - Switching between reading and writing is slow, so don't do it more often
494 * than necessary. 492 * than necessary.
493 * - Optimize for throughput at the expense of latency. This means that streaming
494 * writes will never be interrupted by a read, but if the drive has to seek
495 * before the next write, switch to reading instead if there are any pending
496 * read requests.
495 * - Set the read speed according to current usage pattern. When only reading 497 * - Set the read speed according to current usage pattern. When only reading
496 * from the device, it's best to use the highest possible read speed, but 498 * from the device, it's best to use the highest possible read speed, but
497 * when switching often between reading and writing, it's better to have the 499 * when switching often between reading and writing, it's better to have the
498 * same read and write speeds. 500 * same read and write speeds.
499 * - Reads originating from user space should have higher priority than reads
500 * originating from pkt_gather_data, because some process is usually waiting
501 * on reads of the first kind.
502 */ 501 */
503static void pkt_iosched_process_queue(struct pktcdvd_device *pd) 502static void pkt_iosched_process_queue(struct pktcdvd_device *pd)
504{ 503{
@@ -512,21 +511,24 @@ static void pkt_iosched_process_queue(struct pktcdvd_device *pd)
512 511
513 for (;;) { 512 for (;;) {
514 struct bio *bio; 513 struct bio *bio;
515 int reads_queued, writes_queued, high_prio_read; 514 int reads_queued, writes_queued;
516 515
517 spin_lock(&pd->iosched.lock); 516 spin_lock(&pd->iosched.lock);
518 reads_queued = (pd->iosched.read_queue != NULL); 517 reads_queued = (pd->iosched.read_queue != NULL);
519 writes_queued = (pd->iosched.write_queue != NULL); 518 writes_queued = (pd->iosched.write_queue != NULL);
520 if (!reads_queued)
521 pd->iosched.high_prio_read = 0;
522 high_prio_read = pd->iosched.high_prio_read;
523 spin_unlock(&pd->iosched.lock); 519 spin_unlock(&pd->iosched.lock);
524 520
525 if (!reads_queued && !writes_queued) 521 if (!reads_queued && !writes_queued)
526 break; 522 break;
527 523
528 if (pd->iosched.writing) { 524 if (pd->iosched.writing) {
529 if (high_prio_read || (!writes_queued && reads_queued)) { 525 int need_write_seek = 1;
526 spin_lock(&pd->iosched.lock);
527 bio = pd->iosched.write_queue;
528 spin_unlock(&pd->iosched.lock);
529 if (bio && (bio->bi_sector == pd->iosched.last_write))
530 need_write_seek = 0;
531 if (need_write_seek && reads_queued) {
530 if (atomic_read(&pd->cdrw.pending_bios) > 0) { 532 if (atomic_read(&pd->cdrw.pending_bios) > 0) {
531 VPRINTK("pktcdvd: write, waiting\n"); 533 VPRINTK("pktcdvd: write, waiting\n");
532 break; 534 break;
@@ -559,8 +561,10 @@ static void pkt_iosched_process_queue(struct pktcdvd_device *pd)
559 561
560 if (bio_data_dir(bio) == READ) 562 if (bio_data_dir(bio) == READ)
561 pd->iosched.successive_reads += bio->bi_size >> 10; 563 pd->iosched.successive_reads += bio->bi_size >> 10;
562 else 564 else {
563 pd->iosched.successive_reads = 0; 565 pd->iosched.successive_reads = 0;
566 pd->iosched.last_write = bio->bi_sector + bio_sectors(bio);
567 }
564 if (pd->iosched.successive_reads >= HI_SPEED_SWITCH) { 568 if (pd->iosched.successive_reads >= HI_SPEED_SWITCH) {
565 if (pd->read_speed == pd->write_speed) { 569 if (pd->read_speed == pd->write_speed) {
566 pd->read_speed = MAX_SPEED; 570 pd->read_speed = MAX_SPEED;
@@ -765,7 +769,7 @@ static void pkt_gather_data(struct pktcdvd_device *pd, struct packet_data *pkt)
765 769
766 atomic_inc(&pkt->io_wait); 770 atomic_inc(&pkt->io_wait);
767 bio->bi_rw = READ; 771 bio->bi_rw = READ;
768 pkt_queue_bio(pd, bio, 0); 772 pkt_queue_bio(pd, bio);
769 frames_read++; 773 frames_read++;
770 } 774 }
771 775
@@ -1062,7 +1066,7 @@ static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
1062 1066
1063 atomic_set(&pkt->io_wait, 1); 1067 atomic_set(&pkt->io_wait, 1);
1064 pkt->w_bio->bi_rw = WRITE; 1068 pkt->w_bio->bi_rw = WRITE;
1065 pkt_queue_bio(pd, pkt->w_bio, 0); 1069 pkt_queue_bio(pd, pkt->w_bio);
1066} 1070}
1067 1071
1068static void pkt_finish_packet(struct packet_data *pkt, int uptodate) 1072static 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)
2120 cloned_bio->bi_private = psd; 2124 cloned_bio->bi_private = psd;
2121 cloned_bio->bi_end_io = pkt_end_io_read_cloned; 2125 cloned_bio->bi_end_io = pkt_end_io_read_cloned;
2122 pd->stats.secs_r += bio->bi_size >> 9; 2126 pd->stats.secs_r += bio->bi_size >> 9;
2123 pkt_queue_bio(pd, cloned_bio, 1); 2127 pkt_queue_bio(pd, cloned_bio);
2124 return 0; 2128 return 0;
2125 } 2129 }
2126 2130