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Date: Mon, 15 Jan 2024 12:34:29 -0800 (PST)
From: David Rientjes <rientjes@google.com>
To: Vern Hao <haoxing990@gmail.com>
cc: mgorman@techsingularity.net, akpm@linux-foundation.org, linux-mm@kvack.org, 
    linux-kernel@vger.kernel.org, Xin Hao <vernhao@tencent.com>
Subject: Re: [PATCH RFC v1 2/2] mm, pcp: add more detail info about high
 order page count
In-Reply-To: <20240115093437.87814-3-vernhao@tencent.com>
Message-ID: <4cc41592-2f1a-590a-962e-0cf56082a6b6@google.com>
References: <20240115093437.87814-1-vernhao@tencent.com> <20240115093437.87814-3-vernhao@tencent.com>
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On Mon, 15 Jan 2024, Vern Hao wrote:

> From: Xin Hao <vernhao@tencent.com>
> 
> With this patch, we can see the distribution of pages of different orders on
> each cpu, just like below.
> 	#cat /proc/zoneinfo
>     ....
>     cpu: 2
>               total_count: 14286

I don't think we should be changing the naming of the field if there are 
existing users that parse /proc/zoneinfo.

>                   order0 : 1260
>                   order1 : 13
>                   order2 : 42
>                   order3 : 4
>                   order4 : 0
>                   order5 : 0
>                   order6 : 0
>                   order7 : 0
>                   order8 : 0
>                   order9 : 25
>                   order10: 0
>                   order11: 0
>                   order12: 0
>               high:  14541
>               batch: 63
> 
> Signed-off-by: Xin Hao <vernhao@tencent.com>
> ---
>  include/linux/mmzone.h |  1 +
>  mm/page_alloc.c        |  4 ++++
>  mm/vmstat.c            | 18 ++++++++++++------
>  3 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 883168776fea..55d25b4f51e5 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -684,6 +684,7 @@ enum zone_watermarks {
>  struct per_cpu_pages {
>  	spinlock_t lock;	/* Protects lists field */
>  	int total_count;	/* total number of pages in the list */
> +	int count[NR_PCP_LISTS]; /* per-order page counts */
>  	int high;		/* high watermark, emptying needed */
>  	int high_min;		/* min high watermark */
>  	int high_max;		/* max high watermark */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4e91e429b8d1..7ec2dc5c5ea5 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1228,6 +1228,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
>  			list_del(&page->pcp_list);
>  			count -= nr_pages;
>  			pcp->total_count -= nr_pages;
> +			pcp->count[order] -= 1;
>  
>  			/* MIGRATE_ISOLATE page should not go to pcplists */
>  			VM_BUG_ON_PAGE(is_migrate_isolate(mt), page);
> @@ -2478,6 +2479,7 @@ static void free_unref_page_commit(struct zone *zone, struct per_cpu_pages *pcp,
>  	pindex = order_to_pindex(migratetype, order);
>  	list_add(&page->pcp_list, &pcp->lists[pindex]);
>  	pcp->total_count += 1 << order;
> +	pcp->count[order] += 1;
>  
>  	batch = READ_ONCE(pcp->batch);
>  	/*
> @@ -2858,6 +2860,7 @@ struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
>  					migratetype, alloc_flags);
>  
>  			pcp->total_count += alloced << order;
> +			pcp->count[order] += alloced;
>  			if (unlikely(list_empty(list)))
>  				return NULL;
>  		}
> @@ -2865,6 +2868,7 @@ struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
>  		page = list_first_entry(list, struct page, pcp_list);
>  		list_del(&page->pcp_list);
>  		pcp->total_count -= 1 << order;
> +		pcp->count[order] -= 1;
>  	} while (check_new_pages(page, order));
>  
>  	return page;
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index c1e8096ff0a6..e04300ec450f 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1735,19 +1735,25 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
>  
>  	seq_printf(m, "\n  pagesets");
>  	for_each_online_cpu(i) {
> +		int j;
>  		struct per_cpu_pages *pcp;
>  		struct per_cpu_zonestat __maybe_unused *pzstats;
>  
>  		pcp = per_cpu_ptr(zone->per_cpu_pageset, i);
>  		seq_printf(m,
>  			   "\n    cpu: %i"
> -			   "\n              count: %i"
> -			   "\n              high:  %i"
> -			   "\n              batch: %i",
> +			   "\n              total_count: %i",
>  			   i,
> -			   pcp->total_count,
> -			   pcp->high,
> -			   pcp->batch);
> +			   pcp->total_count);
> +		for (j = 0; j < NR_PCP_LISTS; j++)
> +			seq_printf(m,
> +				   "\n                  order%-2i: %-3i",
> +				   j, pcp->count[j]);
> +		seq_printf(m,
> +                          "\n              high:  %i"
> +                          "\n              batch: %i",
> +                          pcp->high,
> +                          pcp->batch);
>  #ifdef CONFIG_SMP
>  		pzstats = per_cpu_ptr(zone->per_cpu_zonestats, i);
>  		seq_printf(m, "\n  vm stats threshold: %d",
> -- 
> 2.31.1
> 
> 
>