Re: [PATCH 05/10] memcg: add dirty page accounting infrastructure

[Greg Thelen]

Minchan Kim <minchan.kim@xxxxxxxxx> writes:

> On Sun, Oct 03, 2010 at 11:58:00PM -0700, Greg Thelen wrote:
>> Add memcg routines to track dirty, writeback, and unstable_NFS pages.
>> These routines are not yet used by the kernel to count such pages.
>> A later change adds kernel calls to these new routines.
>> 
>> Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
>> Signed-off-by: Andrea Righi <arighi@xxxxxxxxxxx>
>> ---
>>  include/linux/memcontrol.h |    3 +
>>  mm/memcontrol.c            |   89 ++++++++++++++++++++++++++++++++++++++++----
>>  2 files changed, 84 insertions(+), 8 deletions(-)
>> 
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index 7c7bec4..6303da1 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -28,6 +28,9 @@ struct mm_struct;
>>  /* Stats that can be updated by kernel. */
>>  enum mem_cgroup_write_page_stat_item {
>>  	MEMCG_NR_FILE_MAPPED, /* # of pages charged as file rss */
>> +	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 */
>>  };
>>  
>>  extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 267d774..f40839f 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -85,10 +85,13 @@ enum mem_cgroup_stat_index {
>>  	 */
>>  	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
>>  	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
>> -	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
>>  	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
>>  	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
>>  	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
>> +	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
>> +	MEM_CGROUP_STAT_FILE_DIRTY,	/* # of dirty pages in page cache */
>> +	MEM_CGROUP_STAT_FILE_WRITEBACK,		/* # of pages under writeback */
>> +	MEM_CGROUP_STAT_FILE_UNSTABLE_NFS,	/* # of NFS unstable pages */
>>  	MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
>>  	/* incremented at every  pagein/pageout */
>>  	MEM_CGROUP_EVENTS = MEM_CGROUP_STAT_DATA,
>> @@ -1626,6 +1629,48 @@ void mem_cgroup_update_page_stat(struct page *page,
>>  			ClearPageCgroupFileMapped(pc);
>>  		idx = MEM_CGROUP_STAT_FILE_MAPPED;
>>  		break;
>> +
>> +	case MEMCG_NR_FILE_DIRTY:
>> +		/* Use Test{Set,Clear} to only un/charge the memcg once. */
>> +		if (val > 0) {
>> +			if (TestSetPageCgroupFileDirty(pc))
>> +				/* already set */
>
> Nitpick. 
> The comment doesn't give any useful information.
> It looks like redundant. 

I agree.  I removed the four redundant comments you referred to.  Thanks
for the feedback.

>> +				val = 0;
>> +		} else {
>> +			if (!TestClearPageCgroupFileDirty(pc))
>> +				/* already cleared */
>
> Ditto
>
>> +				val = 0;
>> +		}
>> +		idx = MEM_CGROUP_STAT_FILE_DIRTY;
>> +		break;
>> +
>> +	case MEMCG_NR_FILE_WRITEBACK:
>> +		/*
>> +		 * This counter is adjusted while holding the mapping's
>> +		 * tree_lock.  Therefore there is no race between settings and
>> +		 * clearing of this flag.
>> +		 */
>> +		if (val > 0)
>> +			SetPageCgroupFileWriteback(pc);
>> +		else
>> +			ClearPageCgroupFileWriteback(pc);
>> +		idx = MEM_CGROUP_STAT_FILE_WRITEBACK;
>> +		break;
>> +
>> +	case MEMCG_NR_FILE_UNSTABLE_NFS:
>> +		/* Use Test{Set,Clear} to only un/charge the memcg once. */
>> +		if (val > 0) {
>> +			if (TestSetPageCgroupFileUnstableNFS(pc))
>> +				/* already set */
>
> Ditto 
>
>> +				val = 0;
>> +		} else {
>> +			if (!TestClearPageCgroupFileUnstableNFS(pc))
>> +				/* already cleared */
>
> Ditto 
>
>> +				val = 0;
>> +		}
>> +		idx = MEM_CGROUP_STAT_FILE_UNSTABLE_NFS;
>> +		break;
>> +
>>  	default:
>>  		BUG();
>>  	}
>> @@ -2133,6 +2178,16 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
>>  	memcg_check_events(mem, pc->page);
>>  }
>>  
>> +static void mem_cgroup_move_account_page_stat(struct mem_cgroup *from,
>> +					      struct mem_cgroup *to,
>> +					      enum mem_cgroup_stat_index idx)
>> +{
>> +	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
>>   * @pc:	page_cgroup of the page.
>> @@ -2159,13 +2214,18 @@ static void __mem_cgroup_move_account(struct page_cgroup *pc,
>>  	VM_BUG_ON(!PageCgroupUsed(pc));
>>  	VM_BUG_ON(pc->mem_cgroup != from);
>>  
>> -	if (PageCgroupFileMapped(pc)) {
>> -		/* 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 (PageCgroupFileMapped(pc))
>> +		mem_cgroup_move_account_page_stat(from, to,
>> +					MEM_CGROUP_STAT_FILE_MAPPED);
>> +	if (PageCgroupFileDirty(pc))
>> +		mem_cgroup_move_account_page_stat(from, to,
>> +					MEM_CGROUP_STAT_FILE_DIRTY);
>> +	if (PageCgroupFileWriteback(pc))
>> +		mem_cgroup_move_account_page_stat(from, to,
>> +					MEM_CGROUP_STAT_FILE_WRITEBACK);
>> +	if (PageCgroupFileUnstableNFS(pc))
>> +		mem_cgroup_move_account_page_stat(from, to,
>> +					MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
>>  	mem_cgroup_charge_statistics(from, pc, false);
>>  	if (uncharge)
>>  		/* This is not "cancel", but cancel_charge does all we need. */
>> @@ -3545,6 +3605,9 @@ enum {
>>  	MCS_PGPGIN,
>>  	MCS_PGPGOUT,
>>  	MCS_SWAP,
>> +	MCS_FILE_DIRTY,
>> +	MCS_WRITEBACK,
>> +	MCS_UNSTABLE_NFS,
>>  	MCS_INACTIVE_ANON,
>>  	MCS_ACTIVE_ANON,
>>  	MCS_INACTIVE_FILE,
>> @@ -3567,6 +3630,9 @@ struct {
>>  	{"pgpgin", "total_pgpgin"},
>>  	{"pgpgout", "total_pgpgout"},
>>  	{"swap", "total_swap"},
>> +	{"dirty", "total_dirty"},
>> +	{"writeback", "total_writeback"},
>> +	{"nfs", "total_nfs"},
>>  	{"inactive_anon", "total_inactive_anon"},
>>  	{"active_anon", "total_active_anon"},
>>  	{"inactive_file", "total_inactive_file"},
>> @@ -3596,6 +3662,13 @@ mem_cgroup_get_local_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
>>  		s->stat[MCS_SWAP] += val * PAGE_SIZE;
>>  	}
>>  
>> +	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_DIRTY);
>> +	s->stat[MCS_FILE_DIRTY] += val * PAGE_SIZE;
>> +	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_WRITEBACK);
>> +	s->stat[MCS_WRITEBACK] += val * PAGE_SIZE;
>> +	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_UNSTABLE_NFS);
>> +	s->stat[MCS_UNSTABLE_NFS] += val * PAGE_SIZE;
>> +
>>  	/* per zone stat */
>>  	val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
>>  	s->stat[MCS_INACTIVE_ANON] += val * PAGE_SIZE;
>> -- 
>> 1.7.1
>> 
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