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writeback: report dirty thresholds in /proc/vmstat 

The kernel already exposes the user desired thresholds in /proc/sys/vm
with dirty_background_ratio and background_ratio.  But the kernel may
alter the number requested without giving the user any indication that is
the case.

Knowing the actual ratios the kernel is honoring can help app developers
understand how their buffered IO will be sent to the disk.

        $ grep threshold /proc/vmstat
        nr_dirty_threshold 409111
        nr_dirty_background_threshold 818223

Signed-off-by: Michael Rubin <mrubin@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael Rubin 2010-10-26 14:21:36 -07:00 committed by Linus Torvalds
parent 2ac390370a
commit 79da826aee
1 changed files with 25 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
mm/vmstat.c
View File

@ -17,6 +17,7 @@
#include <linux/vmstat.h>
#include <linux/sched.h>
#include <linux/math64.h>
#include <linux/writeback.h>
#ifdef CONFIG_VM_EVENT_COUNTERS
DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
@ -747,6 +748,8 @@ static const char * const vmstat_text[] = {
"nr_shmem",
"nr_dirtied",
"nr_written",
"nr_dirty_threshold",
"nr_dirty_background_threshold",
#ifdef CONFIG_NUMA
"numa_hit",
@ -907,36 +910,44 @@ static const struct file_operations proc_zoneinfo_file_operations = {
.release = seq_release,
};
enum writeback_stat_item {
NR_DIRTY_THRESHOLD,
NR_DIRTY_BG_THRESHOLD,
NR_VM_WRITEBACK_STAT_ITEMS,
};
static void *vmstat_start(struct seq_file *m, loff_t *pos)
{
unsigned long *v;
#ifdef CONFIG_VM_EVENT_COUNTERS
unsigned long *e;
#endif
int i;
int i, stat_items_size;
if (*pos >= ARRAY_SIZE(vmstat_text))
return NULL;
stat_items_size = NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long) +
NR_VM_WRITEBACK_STAT_ITEMS * sizeof(unsigned long);
#ifdef CONFIG_VM_EVENT_COUNTERS
v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long)
+ sizeof(struct vm_event_state), GFP_KERNEL);
#else
v = kmalloc(NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long),
GFP_KERNEL);
stat_items_size += sizeof(struct vm_event_state);
#endif
v = kmalloc(stat_items_size, GFP_KERNEL);
m->private = v;
if (!v)
return ERR_PTR(-ENOMEM);
for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
v[i] = global_page_state(i);
v += NR_VM_ZONE_STAT_ITEMS;
global_dirty_limits(v + NR_DIRTY_BG_THRESHOLD,
v + NR_DIRTY_THRESHOLD);
v += NR_VM_WRITEBACK_STAT_ITEMS;
#ifdef CONFIG_VM_EVENT_COUNTERS
e = v + NR_VM_ZONE_STAT_ITEMS;
all_vm_events(e);
e[PGPGIN] /= 2; /* sectors -> kbytes */
e[PGPGOUT] /= 2;
all_vm_events(v);
v[PGPGIN] /= 2; /* sectors -> kbytes */
v[PGPGOUT] /= 2;
#endif
return v + *pos;
return m->private + *pos;
}
static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)