[Devel] Re: [RFC] [PATCH] memory controller statistics

[YAMAMOTO Takashi]

hi,

thanks for comments.

> Hi,
> 
> On Fri,  7 Sep 2007 12:39:42 +0900 (JST)
> yamamoto at valinux.co.jp (YAMAMOTO Takashi) wrote:
> 
> > +enum mem_container_stat_index {
> > +	/*
> > +	 * for MEM_CONTAINER_TYPE_ALL, usage == pagecache + rss
> > +	 */
> > +	MEMCONT_STAT_PAGECACHE,
> > +	MEMCONT_STAT_RSS,
> > +
> > +	/*
> > +	 * redundant; usage == charge - uncharge
> > +	 */
> > +	MEMCONT_STAT_CHARGE,
> > +	MEMCONT_STAT_UNCHARGE,
> > +
> > +	/*
> > +	 * mostly for debug
> > +	 */
> > +	MEMCONT_STAT_ISOLATE,
> > +	MEMCONT_STAT_ISOLATE_FAIL,
> > +	MEMCONT_STAT_NSTATS,
> > +};
> > +
> please add comments on each statistics name.

sure.

> It's uneasy to catch the meaning of 
> ISOLATE/ISOLATE_FAIL without comments.

they aren't useful for users who don't read the relevant code.
probably they should be just removed.

> > +static const char * const mem_container_stat_desc[] = {
> > +	[MEMCONT_STAT_PAGECACHE] = "page_cache",
> > +	[MEMCONT_STAT_RSS] = "rss",
> > +	[MEMCONT_STAT_CHARGE] = "charge",
> > +	[MEMCONT_STAT_UNCHARGE] = "uncharge",
> > +	[MEMCONT_STAT_ISOLATE] = "isolate",
> > +	[MEMCONT_STAT_ISOLATE_FAIL] = "isolate_fail",
> > +};
> > +
> > +struct mem_container_stat {
> > +	atomic_t count[MEMCONT_STAT_NSTATS];
> > +};
> > +
> > +static void mem_container_stat_inc(struct mem_container_stat * stat,
> > +   enum mem_container_stat_index idx)
> > +{
> > +
> > +	atomic_inc(&stat->count[idx]);
> > +}
> > +
> > +static void mem_container_stat_dec(struct mem_container_stat * stat,
> > +   enum mem_container_stat_index idx)
> > +{
> > +
> > +	atomic_dec(&stat->count[idx]);
> > +}
> > +
> 
> Can we do this accounting as mod_zone_page_state()(in mm/vmstat.c) ?
> (use per-cpu data for accounting.) 

we can do so later.

> > +/* XXX hack; shouldn't be here.  it really belongs to struct page_container. */
> > +#define	PAGE_CONTAINER_CACHE_BIT 	0x1
> > +#define	PAGE_CONTAINER_CACHE 		(1 << PAGE_CONTAINER_CACHE_BIT)
> > +
> 
> Is this used for remebering whether a page is charged as page-cache or not ?

yes.

> > +	page_assign_page_container_flags(page,
> > +	    is_cache ? PAGE_CONTAINER_CACHE : 0, pc);
> > +
> > +	stat = &mem->stat;
> > +	if (is_cache) {
> > +		mem_container_stat_inc(stat, MEMCONT_STAT_PAGECACHE);
> > +	} else {
> > +		mem_container_stat_inc(stat, MEMCONT_STAT_RSS);
> > +	}
> 
> nitpick,in linux style, one-sentence block shouldn't have braces {}.
> 
> ==
> if (is_cache) 
> 	mem_cont...
> else
> 	mem_cont...
> ==

sure.

> > +	mem_container_stat_inc(stat, MEMCONT_STAT_CHARGE);
> >  
> >  	spin_lock_irqsave(&mem->lru_lock, flags);
> >  	list_add(&pc->lru, &mem->active_list);
> > @@ -377,6 +454,12 @@ err:
> >  	return -ENOMEM;
> >  }
> >  
> > +int mem_container_charge(struct page *page, struct mm_struct *mm)
> > +{
> > +
> > +	return mem_container_charge_common(page, mm, 0);
> > +}
> > +
> >  /*
> >   * See if the cached pages should be charged at all?
> >   */
> > @@ -388,7 +471,7 @@ int mem_container_cache_charge(struct pa
> >  
> >  	mem = rcu_dereference(mm->mem_container);
> >  	if (mem->control_type == MEM_CONTAINER_TYPE_ALL)
> > -		return mem_container_charge(page, mm);
> > +		return mem_container_charge_common(page, mm, 1);
> >  	else
> >  		return 0;
> >  }
> > @@ -411,15 +494,29 @@ void mem_container_uncharge(struct page_
> >  		return;
> >  
> >  	if (atomic_dec_and_test(&pc->ref_cnt)) {
> > +		struct mem_container_stat *stat;
> > +		int is_cache;
> > +
> >  		page = pc->page;
> >  		lock_page_container(page);
> >  		mem = pc->mem_container;
> >  		css_put(&mem->css);
> > +		/* XXX */
> This kind of comment is bad.

sure.

> > +		is_cache = (page->page_container & PAGE_CONTAINER_CACHE) != 0;
> >  		page_assign_page_container(page, NULL);
> >  		unlock_page_container(page);
> >  		res_counter_uncharge(&mem->res, 1);
> >  
> > +		stat = &mem->stat;
> > +		if (is_cache) {
> > +			mem_container_stat_dec(stat, MEMCONT_STAT_PAGECACHE);
> > +		} else {
> > +			mem_container_stat_dec(stat, MEMCONT_STAT_RSS);
> > +		}
> > +		mem_container_stat_inc(stat, MEMCONT_STAT_UNCHARGE);
> > +
> >   		spin_lock_irqsave(&mem->lru_lock, flags);
> > +		BUG_ON(list_empty(&pc->lru));
> 
> Why this BUG_ON() is added ?
> 
> Thanks
> -Kame

to ensure that my understanding is correct.

YAMAMOTO Takashi
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