On Mon, Jul 09, 2012 at 11:36:11AM +0800, Sha Zhengju wrote:
> On 07/08/2012 10:53 PM, Fengguang Wu wrote:
> >>@@ -2245,7 +2252,10 @@ int test_set_page_writeback(struct page *page)
> >> {
> >> struct address_space *mapping = page_mapping(page);
> >> int ret;
> >>+ bool locked;
> >>+ unsigned long flags;
> >>
> >>+ mem_cgroup_begin_update_page_stat(page,&locked,&flags);
> >> if (mapping) {
> >> struct backing_dev_info *bdi = mapping->backing_dev_info;
> >> unsigned long flags;
> >>@@ -2272,6 +2282,8 @@ int test_set_page_writeback(struct page *page)
> >> }
> >> if (!ret)
> >> account_page_writeback(page);
> >>+
> >>+ mem_cgroup_end_update_page_stat(page,&locked,&flags);
> >> return ret;
> >>
> >> }
> >Where is the MEM_CGROUP_STAT_FILE_WRITEBACK increased?
> >
>
> It's in account_page_writeback().
>
> void account_page_writeback(struct page *page)
> {
> + mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_WRITEBACK);
> inc_zone_page_state(page, NR_WRITEBACK);
> }
I didn't find that chunk, perhaps it's lost due to rebase..
> There isn't a unified interface to dec/inc writeback accounting, so
> I just follow that.
> Maybe we can rework account_page_writeback() to also account
> dec in?
The current seperate inc/dec paths are fine. It sounds like
over-engineering if going any further.
I'm a bit worried about some 3rd party kernel module to call
account_page_writeback() without mem_cgroup_begin/end_update_page_stat().
Will that lead to serious locking issues, or merely inaccurate
accounting?
Thanks,
Fengguang
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