Re: [PATCH v9 08/13] memcg: dirty page accounting support routines

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 17 Aug 2011 09:15:00 -0700
Greg Thelen <gthelen@google.com> wrote:

> Added memcg dirty page accounting support routines.  These routines are
> used by later changes to provide memcg aware writeback and dirty page
> limiting.  A mem_cgroup_dirty_info() tracepoint is is also included to
> allow for easier understanding of memcg writeback operation.
> 
> Signed-off-by: Greg Thelen <gthelen@google.com>

I have small comments.

> ---
> Changelog since v8:
> - Use 'memcg' rather than 'mem' for local variables and parameters.
>   This is consistent with other memory controller code.
> 
>  include/linux/memcontrol.h        |    9 ++
>  include/trace/events/memcontrol.h |   34 +++++++++
>  mm/memcontrol.c                   |  147 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 190 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 630d3fa..9cc8841 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -36,6 +36,15 @@ enum mem_cgroup_page_stat_item {
>  	MEMCG_NR_FILE_DIRTY, /* # of dirty pages in page cache */
>  	MEMCG_NR_FILE_WRITEBACK, /* # of pages under writeback */
>  	MEMCG_NR_FILE_UNSTABLE_NFS, /* # of NFS unstable pages */
> +	MEMCG_NR_DIRTYABLE_PAGES, /* # of pages that could be dirty */
> +};
> +
> +struct dirty_info {
> +	unsigned long dirty_thresh;
> +	unsigned long background_thresh;
> +	unsigned long nr_file_dirty;
> +	unsigned long nr_writeback;
> +	unsigned long nr_unstable_nfs;
>  };
>  
>  extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
> diff --git a/include/trace/events/memcontrol.h b/include/trace/events/memcontrol.h
> index 781ef9fc..abf1306 100644
> --- a/include/trace/events/memcontrol.h
> +++ b/include/trace/events/memcontrol.h
> @@ -26,6 +26,40 @@ TRACE_EVENT(mem_cgroup_mark_inode_dirty,
>  	TP_printk("ino=%ld css_id=%d", __entry->ino, __entry->css_id)
>  )
>  
> +TRACE_EVENT(mem_cgroup_dirty_info,
> +	TP_PROTO(unsigned short css_id,
> +		 struct dirty_info *dirty_info),
> +
> +	TP_ARGS(css_id, dirty_info),
> +
> +	TP_STRUCT__entry(
> +		__field(unsigned short, css_id)
> +		__field(unsigned long, dirty_thresh)
> +		__field(unsigned long, background_thresh)
> +		__field(unsigned long, nr_file_dirty)
> +		__field(unsigned long, nr_writeback)
> +		__field(unsigned long, nr_unstable_nfs)
> +		),
> +
> +	TP_fast_assign(
> +		__entry->css_id = css_id;
> +		__entry->dirty_thresh = dirty_info->dirty_thresh;
> +		__entry->background_thresh = dirty_info->background_thresh;
> +		__entry->nr_file_dirty = dirty_info->nr_file_dirty;
> +		__entry->nr_writeback = dirty_info->nr_writeback;
> +		__entry->nr_unstable_nfs = dirty_info->nr_unstable_nfs;
> +		),
> +
> +	TP_printk("css_id=%d thresh=%ld bg_thresh=%ld dirty=%ld wb=%ld "
> +		  "unstable_nfs=%ld",
> +		  __entry->css_id,
> +		  __entry->dirty_thresh,
> +		  __entry->background_thresh,
> +		  __entry->nr_file_dirty,
> +		  __entry->nr_writeback,
> +		  __entry->nr_unstable_nfs)
> +)
> +
>  #endif /* _TRACE_MEMCONTROL_H */
>  
>  /* This part must be outside protection */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 4e01699..d54adf4 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1366,6 +1366,11 @@ int mem_cgroup_swappiness(struct mem_cgroup *memcg)
>  	return memcg->swappiness;
>  }
>  
> +static unsigned long dirty_info_reclaimable(struct dirty_info *info)
> +{
> +	return info->nr_file_dirty + info->nr_unstable_nfs;
> +}
> +
>  /*
>   * Return true if the current memory cgroup has local dirty memory settings.
>   * There is an allowed race between the current task migrating in-to/out-of the
> @@ -1396,6 +1401,148 @@ static void mem_cgroup_dirty_param(struct vm_dirty_param *param,
>  	}
>  }
>  
> +static inline bool mem_cgroup_can_swap(struct mem_cgroup *memcg)
> +{
> +	if (!do_swap_account)
> +		return nr_swap_pages > 0;
> +	return !memcg->memsw_is_minimum &&
> +		(res_counter_read_u64(&memcg->memsw, RES_LIMIT) > 0);
> +}

I think

	if (nr_swap_pages == 0)
		return false;
	if (!do_swap_account)
		return true;
	if (memcg->memsw_is_mininum)
		return false;
        if (res_counter_margin(&memcg->memsw) == 0)
		return false;

is a correct check.

> +
> +static s64 mem_cgroup_local_page_stat(struct mem_cgroup *memcg,
> +				      enum mem_cgroup_page_stat_item item)
> +{
> +	s64 ret;
> +
> +	switch (item) {
> +	case MEMCG_NR_FILE_DIRTY:
> +		ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_FILE_DIRTY);
> +		break;
> +	case MEMCG_NR_FILE_WRITEBACK:
> +		ret = mem_cgroup_read_stat(memcg,
> +					   MEM_CGROUP_STAT_FILE_WRITEBACK);
> +		break;
> +	case MEMCG_NR_FILE_UNSTABLE_NFS:
> +		ret = mem_cgroup_read_stat(memcg,
> +					   MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
> +		break;
> +	case MEMCG_NR_DIRTYABLE_PAGES:
> +		ret = mem_cgroup_read_stat(memcg, LRU_ACTIVE_FILE) +
> +			mem_cgroup_read_stat(memcg, LRU_INACTIVE_FILE);
> +		if (mem_cgroup_can_swap(memcg))
> +			ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_ANON) +
> +				mem_cgroup_read_stat(memcg, LRU_INACTIVE_ANON);
> +		break;
> +	default:
> +		BUG();
> +		break;
> +	}
> +	return ret;
> +}
> +
> +/*
> + * Return the number of additional pages that the @memcg cgroup could allocate.
> + * If use_hierarchy is set, then this involves checking parent mem cgroups to
> + * find the cgroup with the smallest free space.
> + */
> +static unsigned long
> +mem_cgroup_hierarchical_free_pages(struct mem_cgroup *memcg)
> +{
> +	u64 free;
> +	unsigned long min_free;
> +
> +	min_free = global_page_state(NR_FREE_PAGES);
> +
> +	while (memcg) {
> +		free = (res_counter_read_u64(&memcg->res, RES_LIMIT) -
> +			res_counter_read_u64(&memcg->res, RES_USAGE)) >>
> +			PAGE_SHIFT;

How about
		free = mem_cgroup_margin(&mem->res);
?

Thanks,
-Kame

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