On Wed, 4 Aug 2010 17:43:24 -0700
Michael Rubin <mrubin@xxxxxxxxxx> wrote:
> To help developers and applications gain visibility into writeback
> behaviour adding four read only sysctl files into /proc/sys/vm.
> These files allow user apps to understand writeback behaviour over time
> and learn how it is impacting their performance.
>
> # cat /proc/sys/vm/pages_dirtied
> 3747
> # cat /proc/sys/vm/pages_entered_writeback
> 3618
>
> Documentation/vm.txt has been updated.
>
> In order to track the "cleaned" and "dirtied" counts we added two
> vm_stat_items. Per memory node stats have been added also. So we can
> see per node granularity:
>
> # cat /sys/devices/system/node/node20/writebackstat
> Node 20 pages_writeback: 0 times
> Node 20 pages_dirtied: 0 times
>
> ...
>
> @@ -1091,6 +1115,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
> {
> if (mapping_cap_account_dirty(mapping)) {
> __inc_zone_page_state(page, NR_FILE_DIRTY);
> + __inc_zone_page_state(page, NR_FILE_PAGES_DIRTIED);
> __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
> task_dirty_inc(current);
> task_io_account_write(PAGE_CACHE_SIZE);
I hope the utility of this change is worth the overhead :(
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -740,6 +740,8 @@ static const char * const vmstat_text[] = {
> "numa_local",
> "numa_other",
> #endif
> + "nr_pages_entered_writeback",
> + "nr_file_pages_dirtied",
>
Wait. These counters appear in /proc/vmstat. So why create standalone
/proc/sys/vm files as well?
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