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md: expose max value of behind writes counter 

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@steeleye.com>
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
Paul Clements 2010-03-08 16:02:37 +11:00 committed by NeilBrown
parent ee8b81b03d
commit 696fcd535b
2 changed files with 29 additions and 1 deletions
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29
drivers/md/bitmap.c
View File

@ -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 = {

1
drivers/md/bitmap.h
View File

@ -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