Fixes up significant read-vs-write regression since 2.5.57.
- Allow separate tuning of read batch expiry and write batch expiry.
block/deadline-iosched.c | 71 +++++++++++++++++++++++++++++++++--------------
1 files changed, 50 insertions(+), 21 deletions(-)
diff -puN drivers/block/deadline-iosched.c~batch-tuning drivers/block/deadline-iosched.c
--- 25/drivers/block/deadline-iosched.c~batch-tuning 2003-02-16 16:38:06.000000000 -0800
+++ 25-akpm/drivers/block/deadline-iosched.c 2003-02-16 16:38:06.000000000 -0800
@@ -22,10 +22,30 @@
/*
* See Documentation/deadline-iosched.txt
*/
-static int read_expire = HZ / 2; /* max time before a read is submitted. */
-static int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
-static int batch_expire = HZ / 4; /* Interval between recalculation of
- writes_starved */
+
+/*
+ * max time before a read is submitted.
+ */
+static int read_expire = HZ / 2;
+
+/*
+ * ditto for writes, these limits are not hard, even
+ * if the disk is capable of satisfying them.
+ */
+static int write_expire = 5 * HZ;
+
+/*
+ * read_batch_expire describes how long we will allow a stream of reads to
+ * persist before looking to see whether it is time to switch over to writes.
+ */
+static int read_batch_expire = HZ / 20;
+
+/*
+ * write_batch_expire describes how long we will allow a stream of writes to
+ * persist before looking to see whether it is time to switch over to reads.
+ */
+static int write_batch_expire = HZ / 40;
+
static int writes_starved = 2; /* max times reads can starve a write */
static const int deadline_hash_shift = 10;
@@ -58,7 +78,7 @@ struct deadline_data {
struct list_head *dispatch; /* driver dispatch queue */
struct list_head *hash; /* request hash */
unsigned long hash_valid_count; /* barrier hash count */
- unsigned int batch_expires; /* time until this batch expires */
+ unsigned int current_batch_expires;
int batch_data_dir; /* current/last batch READ or WRITE */
unsigned int starved; /* times reads have starved writes */
@@ -66,8 +86,8 @@ struct deadline_data {
* settings that change how the i/o scheduler behaves
*/
int fifo_expire[2];
- int batch_expire;
int writes_starved;
+ int batch_expire[2];
int front_merges;
};
@@ -501,12 +521,9 @@ static inline int deadline_check_fifo(st
* deadline_check_batch returns 0 if the current batch has not expired,
* 1 otherwise.
*/
-static inline int deadline_check_batch(struct deadline_data *dd)
+static inline int deadline_batch_expired(struct deadline_data *dd)
{
- if (time_after(jiffies, dd->batch_expires))
- return 1;
-
- return 0;
+ return time_after(jiffies, dd->current_batch_expires);
}
/*
@@ -525,7 +542,7 @@ static int deadline_dispatch_requests(st
*/
drq = dd->next_drq[dd->batch_data_dir];
- if (drq && !deadline_check_batch(dd))
+ if (drq && !deadline_batch_expired(dd))
/* we have a "next request" and our batch is still running */
goto dispatch_request;
@@ -534,7 +551,7 @@ static int deadline_dispatch_requests(st
* data direction (read / write)
*/
- dd->batch_expires = jiffies + dd->batch_expire; /* start a new batch */
+ dd->current_batch_expires = jiffies + dd->batch_expire[WRITE];
if (reads) {
BUG_ON(RB_EMPTY(&dd->sort_list[READ]));
@@ -543,6 +560,7 @@ static int deadline_dispatch_requests(st
goto dispatch_writes;
data_dir = dd->batch_data_dir = READ;
+ dd->current_batch_expires = jiffies + dd->batch_expire[READ];
other_dir = WRITE;
goto dispatch_find_request;
@@ -740,7 +758,8 @@ static int deadline_init(request_queue_t
dd->hash_valid_count = 1;
dd->writes_starved = writes_starved;
dd->front_merges = 1;
- dd->batch_expire = batch_expire;
+ dd->batch_expire[READ] = read_batch_expire;
+ dd->batch_expire[WRITE] = write_batch_expire;
e->elevator_data = dd;
for (i = READ; i <= WRITE; i++) {
@@ -804,7 +823,8 @@ SHOW_FUNCTION(deadline_readexpire_show,
SHOW_FUNCTION(deadline_writeexpire_show, dd->fifo_expire[WRITE]);
SHOW_FUNCTION(deadline_writesstarved_show, dd->writes_starved);
SHOW_FUNCTION(deadline_frontmerges_show, dd->front_merges);
-SHOW_FUNCTION(deadline_batchexpire_show, dd->batch_expire);
+SHOW_FUNCTION(deadline_read_batchexpire_show, dd->batch_expire[READ]);
+SHOW_FUNCTION(deadline_write_batchexpire_show, dd->batch_expire[WRITE]);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
@@ -821,7 +841,10 @@ STORE_FUNCTION(deadline_readexpire_store
STORE_FUNCTION(deadline_writeexpire_store, &dd->fifo_expire[WRITE], 0, INT_MAX);
STORE_FUNCTION(deadline_writesstarved_store, &dd->writes_starved, INT_MIN, INT_MAX);
STORE_FUNCTION(deadline_frontmerges_store, &dd->front_merges, 0, 1);
-STORE_FUNCTION(deadline_batchexpire_store, &dd->batch_expire, 0, INT_MAX);
+STORE_FUNCTION(deadline_read_batchexpire_store,
+ &dd->batch_expire[READ], 0, INT_MAX);
+STORE_FUNCTION(deadline_write_batchexpire_store,
+ &dd->batch_expire[WRITE], 0, INT_MAX);
#undef STORE_FUNCTION
static struct deadline_fs_entry deadline_readexpire_entry = {
@@ -844,10 +867,15 @@ static struct deadline_fs_entry deadline
.show = deadline_frontmerges_show,
.store = deadline_frontmerges_store,
};
-static struct deadline_fs_entry deadline_batchexpire_entry = {
- .attr = {.name = "batch_expire", .mode = S_IRUGO | S_IWUSR },
- .show = deadline_batchexpire_show,
- .store = deadline_batchexpire_store,
+static struct deadline_fs_entry deadline_read_batchexpire_entry = {
+ .attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = deadline_read_batchexpire_show,
+ .store = deadline_read_batchexpire_store,
+};
+static struct deadline_fs_entry deadline_write_batchexpire_entry = {
+ .attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = deadline_write_batchexpire_show,
+ .store = deadline_write_batchexpire_store,
};
static struct attribute *default_attrs[] = {
@@ -855,7 +883,8 @@ static struct attribute *default_attrs[]
&deadline_writeexpire_entry.attr,
&deadline_writesstarved_entry.attr,
&deadline_frontmerges_entry.attr,
- &deadline_batchexpire_entry.attr,
+ &deadline_read_batchexpire_entry.attr,
+ &deadline_write_batchexpire_entry.attr,
NULL,
};
_