Thank you for your quick reply and comments.
On Thu, Aug 19, 2010 at 8:16 PM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> On Thu, Aug 19, 2010 at 01:57:27PM -0700, Michael Rubin wrote:
>> The kernel already exposes the desired thresholds in /proc/sys/vm with
>> dirty_background_ratio and background_ratio. Instead the kernel may
>> alter the number requested without giving the user any indication that
>> is the case.
>
> You mean the 5% lower bound in global_dirty_limits()? Let's rip it :)
>
>> 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_pages_dirty_threshold 409111
>> nr_pages_dirty_background_threshold 818223
>
> It's redundant to have _pages in the names. /proc/vmstat has the
> tradition to use nr_dirty instead of nr_pages_dirty.
>
> They do look like useful counters to export, especially when we do
> dynamic dirty limits in future.
>
>> Signed-off-by: Michael Rubin <mrubin@xxxxxxxxxx>
>> ---
>> include/linux/mmzone.h | 2 ++
>> mm/vmstat.c | 8 ++++++++
>> 2 files changed, 10 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index f160481..7c4a3bf 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -114,6 +114,8 @@ enum zone_stat_item {
>> #endif
>> NR_PAGES_ENTERED_WRITEBACK, /* number of times pages enter writeback */
>> NR_FILE_PAGES_DIRTIED, /* number of times pages get dirtied */
>> + NR_PAGES_DIRTY_THRESHOLD, /* writeback threshold */
>> + NR_PAGES_DIRTY_BG_THRESHOLD,/* bg writeback threshold */
>
> s/_PAGES//
Cool. Thanks.
>
>> NR_VM_ZONE_STAT_ITEMS };
>>
>> /*
>> diff --git a/mm/vmstat.c b/mm/vmstat.c
>> index e177a40..8b5bc78 100644
>> --- a/mm/vmstat.c
>> +++ b/mm/vmstat.c
>> @@ -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}};
>> @@ -742,6 +743,8 @@ static const char * const vmstat_text[] = {
>> #endif
>> "nr_pages_entered_writeback",
>> "nr_file_pages_dirtied",
>> + "nr_pages_dirty_threshold",
>> + "nr_pages_dirty_background_threshold",
>
> s/_pages//
Got it.
>
>> #ifdef CONFIG_VM_EVENT_COUNTERS
>> "pgpgin",
>> @@ -901,6 +904,7 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
>> #ifdef CONFIG_VM_EVENT_COUNTERS
>> unsigned long *e;
>> #endif
>> + unsigned long dirty_thresh, dirty_bg_thresh;
>> int i;
>>
>> if (*pos >= ARRAY_SIZE(vmstat_text))
>> @@ -918,6 +922,10 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
>> return ERR_PTR(-ENOMEM);
>> for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
>> v[i] = global_page_state(i);
>> +
>> + get_dirty_limits(&dirty_thresh, &dirty_bg_thresh, NULL, NULL);
>
> 2.6.36-rc1 will need this:
>
> global_dirty_limits(v + NR_DIRTY_THRESHOLD, v + NR_DIRTY_BG_THRESHOLD);
Yeah I noticed when I rebased. Thanks.
mrubin
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