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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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38
lib/proportions.c
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@@ -73,12 +73,6 @@
#include <linux/proportions.h>
#include <linux/rcupdate.h>
/*
* Limit the time part in order to ensure there are some bits left for the
* cycle counter.
*/
#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
int prop_descriptor_init(struct prop_descriptor *pd, int shift)
{
int err;
@@ -267,6 +261,38 @@ void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
prop_put_global(pd, pg);
}
/*
* identical to __prop_inc_percpu, except that it limits this pl's fraction to
* @frac/PROP_FRAC_BASE by ignoring events when this limit has been exceeded.
*/
void __prop_inc_percpu_max(struct prop_descriptor *pd,
struct prop_local_percpu *pl, long frac)
{
struct prop_global *pg = prop_get_global(pd);
prop_norm_percpu(pg, pl);
if (unlikely(frac != PROP_FRAC_BASE)) {
unsigned long period_2 = 1UL << (pg->shift - 1);
unsigned long counter_mask = period_2 - 1;
unsigned long global_count;
long numerator, denominator;
numerator = percpu_counter_read_positive(&pl->events);
global_count = percpu_counter_read(&pg->events);
denominator = period_2 + (global_count & counter_mask);
if (numerator > ((denominator * frac) >> PROP_FRAC_SHIFT))
goto out_put;
}
percpu_counter_add(&pl->events, 1);
percpu_counter_add(&pg->events, 1);
out_put:
prop_put_global(pd, pg);
}
/*
* Obtain a fraction of this proportion
*