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mm: bdi: move statistics to debugfs
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Move BDI statistics to debugfs:

   /sys/kernel/debug/bdi/<bdi>/stats

Use postcore_initcall() to initialize the sysfs class and debugfs,
because debugfs is initialized in core_initcall().

Update descriptions in ABI documentation.

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>
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Miklos Szeredi authored and Linus Torvalds committed Apr 30, 2008
1 parent a42dde0 commit 76f1418
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43 changes: 15 additions & 28 deletions Documentation/ABI/testing/sysfs-class-bdi
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,8 @@ Date: January 2008
Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:

Provide a place in sysfs for the backing_dev_info object.
This allows us to see and set the various BDI specific variables.
Provide a place in sysfs for the backing_dev_info object. This allows
setting and retrieving various BDI specific variables.

The <bdi> identifier can be either of the following:

Expand All @@ -26,34 +26,21 @@ read_ahead_kb (read-write)

Size of the read-ahead window in kilobytes

reclaimable_kb (read-only)

Reclaimable (dirty or unstable) memory destined for writeback
to this device

writeback_kb (read-only)

Memory currently under writeback to this device

dirty_kb (read-only)

Global threshold for reclaimable + writeback memory

bdi_dirty_kb (read-only)

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.
If min_ratio would become larger than the current max_ratio,
then also EINVAL is returned. The default is zero
Under normal circumstances each device is given a part of the
total write-back cache that relates to its current average
writeout speed in relation to the other devices.

The 'min_ratio' parameter allows assigning a minimum
percentage of the write-back cache to a particular device.
For example, this is useful for providing a minimum QoS.

max_ratio (read-write)

Maximal percentage of global dirty threshold allocated to this
bdi. If max_ratio would become smaller than the current
min_ratio, then EINVAL is returned. The default is 100
Allows limiting a particular device to use not more than the
given percentage of the write-back cache. This is useful in
situations where we want to avoid one device taking all or
most of the write-back cache. For example in case of an NFS
mount that is prone to get stuck, or a FUSE mount which cannot
be trusted to play fair.
6 changes: 6 additions & 0 deletions include/linux/backing-dev.h
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@

struct page;
struct device;
struct dentry;

/*
* Bits in backing_dev_info.state
Expand Down Expand Up @@ -55,6 +56,11 @@ struct backing_dev_info {
unsigned int max_ratio, max_prop_frac;

struct device *dev;

#ifdef CONFIG_DEBUG_FS
struct dentry *debug_dir;
struct dentry *debug_stats;
#endif
};

int bdi_init(struct backing_dev_info *bdi);
Expand Down
98 changes: 78 additions & 20 deletions mm/backing-dev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,80 @@

static struct class *bdi_class;

#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#include <linux/seq_file.h>

static struct dentry *bdi_debug_root;

static void bdi_debug_init(void)
{
bdi_debug_root = debugfs_create_dir("bdi", NULL);
}

static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
struct backing_dev_info *bdi = m->private;
long background_thresh;
long dirty_thresh;
long bdi_thresh;

get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);

#define K(x) ((x) << (PAGE_SHIFT - 10))
seq_printf(m,
"BdiWriteback: %8lu kB\n"
"BdiReclaimable: %8lu kB\n"
"BdiDirtyThresh: %8lu kB\n"
"DirtyThresh: %8lu kB\n"
"BackgroundThresh: %8lu kB\n",
(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
K(bdi_thresh),
K(dirty_thresh),
K(background_thresh));
#undef K

return 0;
}

static int bdi_debug_stats_open(struct inode *inode, struct file *file)
{
return single_open(file, bdi_debug_stats_show, inode->i_private);
}

static const struct file_operations bdi_debug_stats_fops = {
.open = bdi_debug_stats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};

static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
{
bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
bdi, &bdi_debug_stats_fops);
}

static void bdi_debug_unregister(struct backing_dev_info *bdi)
{
debugfs_remove(bdi->debug_stats);
debugfs_remove(bdi->debug_dir);
}
#else
static inline void bdi_debug_init(void)
{
}
static inline void bdi_debug_register(struct backing_dev_info *bdi,
const char *name)
{
}
static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
{
}
#endif

static ssize_t read_ahead_kb_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
Expand Down Expand Up @@ -40,21 +114,6 @@ static ssize_t name##_show(struct device *dev, \

BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))

BDI_SHOW(reclaimable_kb, K(bdi_stat(bdi, BDI_RECLAIMABLE)))
BDI_SHOW(writeback_kb, K(bdi_stat(bdi, BDI_WRITEBACK)))

static inline unsigned long get_dirty(struct backing_dev_info *bdi, int i)
{
unsigned long thresh[3];

get_dirty_limits(&thresh[0], &thresh[1], &thresh[2], bdi);

return thresh[i];
}

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)
{
Expand Down Expand Up @@ -95,10 +154,6 @@ BDI_SHOW(max_ratio, bdi->max_ratio)

static struct device_attribute bdi_dev_attrs[] = {
__ATTR_RW(read_ahead_kb),
__ATTR_RO(reclaimable_kb),
__ATTR_RO(writeback_kb),
__ATTR_RO(dirty_kb),
__ATTR_RO(bdi_dirty_kb),
__ATTR_RW(min_ratio),
__ATTR_RW(max_ratio),
__ATTR_NULL,
Expand All @@ -108,10 +163,11 @@ static __init int bdi_class_init(void)
{
bdi_class = class_create(THIS_MODULE, "bdi");
bdi_class->dev_attrs = bdi_dev_attrs;
bdi_debug_init();
return 0;
}

core_initcall(bdi_class_init);
postcore_initcall(bdi_class_init);

int bdi_register(struct backing_dev_info *bdi, struct device *parent,
const char *fmt, ...)
Expand All @@ -136,6 +192,7 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,

bdi->dev = dev;
dev_set_drvdata(bdi->dev, bdi);
bdi_debug_register(bdi, name);

exit:
kfree(name);
Expand All @@ -152,6 +209,7 @@ EXPORT_SYMBOL(bdi_register_dev);
void bdi_unregister(struct backing_dev_info *bdi)
{
if (bdi->dev) {
bdi_debug_unregister(bdi);
device_unregister(bdi->dev);
bdi->dev = NULL;
}
Expand Down

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