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Subject[PATCH 21/33] readahead: initial method - user recommended size
backing_dev_info.ra_pages0 is a user configurable parameter that controls
the readahead size on start-of-file.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---
block/ll_rw_blk.c | 30 ++++++++++++++++++++++++++++++
1 files changed, 30 insertions(+)
--- linux-2.6.17-rc4-mm3.orig/block/ll_rw_blk.c
+++ linux-2.6.17-rc4-mm3/block/ll_rw_blk.c
@@ -3811,6 +3811,29 @@ queue_ra_store(struct request_queue *q,
return ret;
}

+static ssize_t queue_initial_ra_show(struct request_queue *q, char *page)
+{
+ int kb = q->backing_dev_info.ra_pages0 << (PAGE_CACHE_SHIFT - 10);
+
+ return queue_var_show(kb, (page));
+}
+
+static ssize_t
+queue_initial_ra_store(struct request_queue *q, const char *page, size_t count)
+{
+ unsigned long kb, ra;
+ ssize_t ret = queue_var_store(&kb, page, count);
+
+ ra = kb >> (PAGE_CACHE_SHIFT - 10);
+ q->backing_dev_info.ra_pages0 = ra;
+
+ ra = kb * 1024;
+ if (q->backing_dev_info.ra_expect_bytes > ra)
+ q->backing_dev_info.ra_expect_bytes = ra;
+
+ return ret;
+}
+
static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
{
int max_sectors_kb = q->max_sectors >> 1;
@@ -3868,6 +3891,12 @@ static struct queue_sysfs_entry queue_ra
.store = queue_ra_store,
};

+static struct queue_sysfs_entry queue_initial_ra_entry = {
+ .attr = {.name = "initial_ra_kb", .mode = S_IRUGO | S_IWUSR },
+ .show = queue_initial_ra_show,
+ .store = queue_initial_ra_store,
+};
+
static struct queue_sysfs_entry queue_max_sectors_entry = {
.attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
.show = queue_max_sectors_show,
@@ -3888,6 +3917,7 @@ static struct queue_sysfs_entry queue_io
static struct attribute *default_attrs[] = {
&queue_requests_entry.attr,
&queue_ra_entry.attr,
+ &queue_initial_ra_entry.attr,
&queue_max_hw_sectors_entry.attr,
&queue_max_sectors_entry.attr,
&queue_iosched_entry.attr,
--
-
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