From: Paul Clements <paul.clements@xxxxxxxxxxxx>
Keep track of the maximum number of concurrent write-behind requests
for an md array and exposed this number in sysfs at
md/bitmap/max_backlog_used
Writing any value to this file will clear it.
This allows userspace to be involved in tuning bitmap/backlog.
Signed-off-by: Paul Clements <paul.clements@xxxxxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
drivers/md/bitmap.c | 29 ++++++++++++++++++++++++++++-
drivers/md/bitmap.h | 1 +
2 files changed, 29 insertions(+), 1 deletions(-)
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 26ac8aa..6279393 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1292,9 +1292,14 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
if (!bitmap) return 0;
if (behind) {
+ int bw;
atomic_inc(&bitmap->behind_writes);
+ bw = atomic_read(&bitmap->behind_writes);
+ if (bw > bitmap->behind_writes_used)
+ bitmap->behind_writes_used = bw;
+
PRINTK(KERN_DEBUG "inc write-behind count %d/%d\n",
- atomic_read(&bitmap->behind_writes), bitmap->max_write_behind);
+ bw, bitmap->max_write_behind);
}
while (sectors) {
@@ -2006,6 +2011,27 @@ static ssize_t can_clear_store(mddev_t *mddev, const char *buf, size_t len)
static struct md_sysfs_entry bitmap_can_clear =
__ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store);
+static ssize_t
+behind_writes_used_show(mddev_t *mddev, char *page)
+{
+ if (mddev->bitmap == NULL)
+ return sprintf(page, "0\n");
+ return sprintf(page, "%lu\n",
+ mddev->bitmap->behind_writes_used);
+}
+
+static ssize_t
+behind_writes_used_reset(mddev_t *mddev, const char *buf, size_t len)
+{
+ if (mddev->bitmap)
+ mddev->bitmap->behind_writes_used = 0;
+ return len;
+}
+
+static struct md_sysfs_entry max_backlog_used =
+__ATTR(max_backlog_used, S_IRUGO | S_IWUSR,
+ behind_writes_used_show, behind_writes_used_reset);
+
static struct attribute *md_bitmap_attrs[] = {
&bitmap_location.attr,
&bitmap_timeout.attr,
@@ -2013,6 +2039,7 @@ static struct attribute *md_bitmap_attrs[] = {
&bitmap_chunksize.attr,
&bitmap_metadata.attr,
&bitmap_can_clear.attr,
+ &max_backlog_used.attr,
NULL
};
struct attribute_group md_bitmap_group = {
diff --git a/drivers/md/bitmap.h b/drivers/md/bitmap.h
index cb821d7..aa82b7c 100644
--- a/drivers/md/bitmap.h
+++ b/drivers/md/bitmap.h
@@ -227,6 +227,7 @@ struct bitmap {
int allclean;
atomic_t behind_writes;
+ unsigned long behind_writes_used; /* highest actual value at runtime */
/*
* the bitmap daemon - periodically wakes up and sweeps the bitmap
--
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