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Date: Fri, 15 Jun 2012 08:32:43 -0700
From: Greg Thelen <gthelen@...gle.com>
To: Sha Zhengju <handai.szj@...il.com>
Cc: linux-mm@...ck.org, cgroups@...r.kernel.org,
kamezawa.hiroyu@...fujitsu.com, yinghan@...gle.com,
akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
Sha Zhengju <handai.szj@...bao.com>
Subject: Re: [PATCH 2/2] memcg: add per cgroup dirty pages accounting
On Fri, Jun 15 2012, Sha Zhengju wrote:
> This patch adds memcg routines to count dirty pages. I notice that
> the list has talked about per-cgroup dirty page limiting
> (http://lwn.net/Articles/455341/) before, but it did not get merged.
Good timing, I was just about to make another effort to get some of
these patches upstream. Like you, I was going to start with some basic
counters.
Your approach is similar to what I have in mind. While it is good to
use the existing PageDirty flag, rather than introducing a new
page_cgroup flag, there are locking complications (see below) to handle
races between moving pages between memcg and the pages being {un}marked
dirty.
> I've no idea how is this going now, but maybe we can add per cgroup
> dirty pages accounting first. This allows the memory controller to
> maintain an accurate view of the amount of its memory that is dirty
> and can provide some infomation while group's direct reclaim is working.
>
> After commit 89c06bd5 (memcg: use new logic for page stat accounting),
> we do not need per page_cgroup flag anymore and can directly use
> struct page flag.
>
>
> Signed-off-by: Sha Zhengju <handai.szj@...bao.com>
> ---
> include/linux/memcontrol.h | 1 +
> mm/filemap.c | 1 +
> mm/memcontrol.c | 32 +++++++++++++++++++++++++-------
> mm/page-writeback.c | 2 ++
> mm/truncate.c | 1 +
> 5 files changed, 30 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index a337c2e..8154ade 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -39,6 +39,7 @@ enum mem_cgroup_stat_index {
> MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
> MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
> + MEM_CGROUP_STAT_FILE_DIRTY, /* # of dirty pages in page cache */
> MEM_CGROUP_STAT_NSTATS,
> };
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 79c4b2b..5b5c121 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -141,6 +141,7 @@ void __delete_from_page_cache(struct page *page)
> * having removed the page entirely.
> */
> if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
> + mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_DIRTY);
You need to use mem_cgroup_{begin,end}_update_page_stat around critical
sections that:
1) check PageDirty
2) update MEM_CGROUP_STAT_FILE_DIRTY counter
This protects against the page from being moved between memcg while
accounting. Same comment applies to all of your new calls to
mem_cgroup_{dec,inc}_page_stat. For usage pattern, see
page_add_file_rmap.
> dec_zone_page_state(page, NR_FILE_DIRTY);
> dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
> }
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9102b8c..d200ad1 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2548,6 +2548,18 @@ void mem_cgroup_split_huge_fixup(struct page *head)
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> +static inline
> +void mem_cgroup_move_account_page_stat(struct mem_cgroup *from,
> + struct mem_cgroup *to,
> + enum mem_cgroup_stat_index idx)
> +{
> + /* Update stat data for mem_cgroup */
> + preempt_disable();
> + __this_cpu_dec(from->stat->count[idx]);
> + __this_cpu_inc(to->stat->count[idx]);
> + preempt_enable();
> +}
> +
> /**
> * mem_cgroup_move_account - move account of the page
> * @page: the page
> @@ -2597,13 +2609,14 @@ static int mem_cgroup_move_account(struct page *page,
>
> move_lock_mem_cgroup(from, &flags);
>
> - if (!anon && page_mapped(page)) {
> - /* Update mapped_file data for mem_cgroup */
> - preempt_disable();
> - __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> - __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> - preempt_enable();
> - }
> + if (!anon && page_mapped(page))
> + mem_cgroup_move_account_page_stat(from, to,
> + MEM_CGROUP_STAT_FILE_MAPPED);
> +
> + if (PageDirty(page))
> + mem_cgroup_move_account_page_stat(from, to,
> + MEM_CGROUP_STAT_FILE_DIRTY);
> +
> mem_cgroup_charge_statistics(from, anon, -nr_pages);
> if (uncharge)
> /* This is not "cancel", but cancel_charge does all we need. */
> @@ -4023,6 +4036,7 @@ enum {
> MCS_SWAP,
> MCS_PGFAULT,
> MCS_PGMAJFAULT,
> + MCS_FILE_DIRTY,
> MCS_INACTIVE_ANON,
> MCS_ACTIVE_ANON,
> MCS_INACTIVE_FILE,
> @@ -4047,6 +4061,7 @@ struct {
> {"swap", "total_swap"},
> {"pgfault", "total_pgfault"},
> {"pgmajfault", "total_pgmajfault"},
> + {"dirty", "total_dirty"},
Please add something to Documentation/cgroups/memory.txt describing this
new user visible data. See my previous patch
http://thread.gmane.org/gmane.linux.kernel.mm/67114 for example text.
> {"inactive_anon", "total_inactive_anon"},
> {"active_anon", "total_active_anon"},
> {"inactive_file", "total_inactive_file"},
> @@ -4080,6 +4095,9 @@ mem_cgroup_get_local_stat(struct mem_cgroup *memcg, struct mcs_total_stat *s)
> val = mem_cgroup_read_events(memcg, MEM_CGROUP_EVENTS_PGMAJFAULT);
> s->stat[MCS_PGMAJFAULT] += val;
>
> + val = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_FILE_DIRTY);
> + s->stat[MCS_FILE_DIRTY] += val * PAGE_SIZE;
> +
> /* per zone stat */
> val = mem_cgroup_nr_lru_pages(memcg, BIT(LRU_INACTIVE_ANON));
> s->stat[MCS_INACTIVE_ANON] += val * PAGE_SIZE;
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 26adea8..b17c692 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1936,6 +1936,7 @@ int __set_page_dirty_no_writeback(struct page *page)
> void account_page_dirtied(struct page *page, struct address_space *mapping)
> {
> if (mapping_cap_account_dirty(mapping)) {
> + mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_DIRTY);
> __inc_zone_page_state(page, NR_FILE_DIRTY);
> __inc_zone_page_state(page, NR_DIRTIED);
> __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
> @@ -2155,6 +2156,7 @@ int clear_page_dirty_for_io(struct page *page)
> * for more comments.
> */
> if (TestClearPageDirty(page)) {
> + mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_DIRTY);
> dec_zone_page_state(page, NR_FILE_DIRTY);
> dec_bdi_stat(mapping->backing_dev_info,
> BDI_RECLAIMABLE);
> diff --git a/mm/truncate.c b/mm/truncate.c
> index 61a183b..fe8363e 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -76,6 +76,7 @@ void cancel_dirty_page(struct page *page, unsigned int account_size)
> if (TestClearPageDirty(page)) {
> struct address_space *mapping = page->mapping;
> if (mapping && mapping_cap_account_dirty(mapping)) {
> + mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_DIRTY);
> dec_zone_page_state(page, NR_FILE_DIRTY);
> dec_bdi_stat(mapping->backing_dev_info,
> BDI_RECLAIMABLE);
--
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