Under normal circumstances each device is given a part of the total write-back
cache that relates to its current avg writeout speed in relation to the other
devices.
min_ratio - allows one to assign a minimum portion of the write-back cache to
a particular device. This is useful in situations where you might want to
provide a minimum QoS. (One request for this feature came from flash based
storage people who wanted to avoid writing out at all costs - they of course
needed some pdflush hacks as well)
max_ratio - allows one to assign a maximum portion of the dirty limit to a
particular device. This is useful in situations where you want to avoid one
device taking all or most of the write-back cache. Eg. an NFS mount that is
prone to get stuck, or a FUSE mount which you don't trust to play fair.
Add "min_ratio" to /sys/class/bdi. This indicates the minimum percentage of
the global dirty threshold allocated to this bdi.
[mszeredi@suse.cz]
- fix parsing in min_ratio_store()
- document new sysfs attribute
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Current threshold on this BDI for reclaimable + writeback
memory
Current threshold on this BDI for reclaimable + writeback
memory
+min_ratio (read-write)
+
+ Minimal percentage of global dirty threshold allocated to this
+ bdi. If the value written to this file would make the the sum
+ of all min_ratio values exceed 100, then EINVAL is returned.
+ The default is zero
struct prop_local_percpu completions;
int dirty_exceeded;
struct prop_local_percpu completions;
int dirty_exceeded;
+ unsigned int min_ratio;
+
+int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
+
/*
* Flags in backing_dev_info::capability
* - The first two flags control whether dirty pages will contribute to the
/*
* Flags in backing_dev_info::capability
* - The first two flags control whether dirty pages will contribute to the
BDI_SHOW(dirty_kb, K(get_dirty(bdi, 1)))
BDI_SHOW(bdi_dirty_kb, K(get_dirty(bdi, 2)))
BDI_SHOW(dirty_kb, K(get_dirty(bdi, 1)))
BDI_SHOW(bdi_dirty_kb, K(get_dirty(bdi, 2)))
+static ssize_t min_ratio_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+ char *end;
+ unsigned int ratio;
+ ssize_t ret = -EINVAL;
+
+ ratio = simple_strtoul(buf, &end, 10);
+ if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
+ ret = bdi_set_min_ratio(bdi, ratio);
+ if (!ret)
+ ret = count;
+ }
+ return ret;
+}
+BDI_SHOW(min_ratio, bdi->min_ratio)
+
#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
static struct device_attribute bdi_dev_attrs[] = {
#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
static struct device_attribute bdi_dev_attrs[] = {
__ATTR_RO(writeback_kb),
__ATTR_RO(dirty_kb),
__ATTR_RO(bdi_dirty_kb),
__ATTR_RO(writeback_kb),
__ATTR_RO(dirty_kb),
__ATTR_RO(bdi_dirty_kb),
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
if (err)
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
if (err)
+ *
+ */
+static DEFINE_SPINLOCK(bdi_lock);
+static unsigned int bdi_min_ratio;
+
+int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
+{
+ int ret = 0;
+ unsigned long flags;
+
+ spin_lock_irqsave(&bdi_lock, flags);
+ min_ratio -= bdi->min_ratio;
+ if (bdi_min_ratio + min_ratio < 100) {
+ bdi_min_ratio += min_ratio;
+ bdi->min_ratio += min_ratio;
+ } else
+ ret = -EINVAL;
+ spin_unlock_irqrestore(&bdi_lock, flags);
+
+ return ret;
+}
+
+/*
* Work out the current dirty-memory clamping and background writeout
* thresholds.
*
* Work out the current dirty-memory clamping and background writeout
* thresholds.
*
*pdirty = dirty;
if (bdi) {
*pdirty = dirty;
if (bdi) {
long numerator, denominator;
/*
long numerator, denominator;
/*
*/
bdi_writeout_fraction(bdi, &numerator, &denominator);
*/
bdi_writeout_fraction(bdi, &numerator, &denominator);
+ bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
bdi_dirty *= numerator;
do_div(bdi_dirty, denominator);
bdi_dirty *= numerator;
do_div(bdi_dirty, denominator);
+ bdi_dirty += (dirty * bdi->min_ratio) / 100;
*pbdi_dirty = bdi_dirty;
clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);
*pbdi_dirty = bdi_dirty;
clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);