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mm: bdi: allow setting a maximum for the bdi dirty limit

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Add "max_ratio" to /sys/class/bdi.  This indicates the maximum percentage of
the global dirty threshold allocated to this bdi.

[mszeredi@suse.cz]

 - fix parsing in max_ratio_store().
 - export bdi_set_max_ratio() to modules
 - limit bdi_dirty with bdi->max_ratio
 - 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>
This commit is contained in:
Peter Zijlstra
2008-04-30 00:54:36 -07:00
committed by Linus Torvalds
parent 189d3c4a94
commit a42dde0415
6 changed files with 111 additions and 13 deletions
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41
mm/page-writeback.c
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@@ -164,7 +164,8 @@ int dirty_ratio_handler(struct ctl_table *table, int write,
*/
static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
{
__prop_inc_percpu(&vm_completions, &bdi->completions);
__prop_inc_percpu_max(&vm_completions, &bdi->completions,
bdi->max_prop_frac);
}
static inline void task_dirty_inc(struct task_struct *tsk)
@@ -254,17 +255,43 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
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
if (min_ratio > bdi->max_ratio) {
ret = -EINVAL;
} else {
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;
}
int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
{
unsigned long flags;
int ret = 0;
if (max_ratio > 100)
return -EINVAL;
spin_lock_irqsave(&bdi_lock, flags);
if (bdi->min_ratio > max_ratio) {
ret = -EINVAL;
} else {
bdi->max_ratio = max_ratio;
bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
}
spin_unlock_irqrestore(&bdi_lock, flags);
return ret;
}
EXPORT_SYMBOL(bdi_set_max_ratio);
/*
* Work out the current dirty-memory clamping and background writeout
* thresholds.
@@ -365,6 +392,8 @@ get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
bdi_dirty *= numerator;
do_div(bdi_dirty, denominator);
bdi_dirty += (dirty * bdi->min_ratio) / 100;
if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
bdi_dirty = dirty * bdi->max_ratio / 100;
*pbdi_dirty = bdi_dirty;
clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);