Messages in this thread | | | Date | Mon, 09 Jul 2012 13:18:07 +0900 | From | Kamezawa Hiroyuki <> | Subject | Re: [PATCH 6/7] memcg: add per cgroup writeback pages accounting |
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(2012/07/09 13:14), Fengguang Wu wrote: > 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? >
Ah, Hm. Maybe it's better to add some debug check in mem_cgroup_update_page_stat(). rcu_read_lock_held() or some.
Thanks, -Kame
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