Re: [PATCH] mm: hide per-cpu lists in output of show_mem()

[Michal Hocko]

On Fri 20-02-15 17:39:42, Konstantin Khlebnikov wrote:
> This makes show_mem() much less verbose at huge machines. Instead of
> huge and almost useless dump of counters for each per-zone per-cpu
> lists this patch prints sum of these counters for each zone (free_pcp)
> and size of per-cpu list for current cpu (local_pcp).

I like this! I do not remember when I found this information useful
while debugging either an allocation failure warning or OOM killer
report.

> Flag SHOW_MEM_PERCPU_LISTS reverts old verbose mode.

Nobody seems to be using this flag so why bother?

> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxx>

> ---
>  include/linux/mm.h |    1 +
>  mm/page_alloc.c    |   32 +++++++++++++++++++++++++-------
>  2 files changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 028565a..0538de0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1126,6 +1126,7 @@ extern void pagefault_out_of_memory(void);
>   * various contexts.
>   */
>  #define SHOW_MEM_FILTER_NODES		(0x0001u)	/* disallowed nodes */
> +#define SHOW_MEM_PERCPU_LISTS		(0x0002u)	/* per-zone per-cpu */
>  
>  extern void show_free_areas(unsigned int flags);
>  extern bool skip_free_areas_node(unsigned int flags, int nid);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a47f0b2..e591f3b 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3198,20 +3198,29 @@ static void show_migration_types(unsigned char type)
>   */
>  void show_free_areas(unsigned int filter)
>  {
> +	unsigned long free_pcp = 0;
>  	int cpu;
>  	struct zone *zone;
>  
>  	for_each_populated_zone(zone) {
>  		if (skip_free_areas_node(filter, zone_to_nid(zone)))
>  			continue;
> -		show_node(zone);
> -		printk("%s per-cpu:\n", zone->name);
> +
> +		if (filter & SHOW_MEM_PERCPU_LISTS) {
> +			show_node(zone);
> +			printk("%s per-cpu:\n", zone->name);
> +		}
>  
>  		for_each_online_cpu(cpu) {
>  			struct per_cpu_pageset *pageset;
>  
>  			pageset = per_cpu_ptr(zone->pageset, cpu);
>  
> +			free_pcp += pageset->pcp.count;
> +
> +			if (!(filter & SHOW_MEM_PERCPU_LISTS))
> +				continue;
> +
>  			printk("CPU %4d: hi:%5d, btch:%4d usd:%4d\n",
>  			       cpu, pageset->pcp.high,
>  			       pageset->pcp.batch, pageset->pcp.count);
> @@ -3220,11 +3229,10 @@ void show_free_areas(unsigned int filter)
>  
>  	printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
>  		" active_file:%lu inactive_file:%lu isolated_file:%lu\n"
> -		" unevictable:%lu"
> -		" dirty:%lu writeback:%lu unstable:%lu\n"
> -		" free:%lu slab_reclaimable:%lu slab_unreclaimable:%lu\n"
> +		" unevictable:%lu dirty:%lu writeback:%lu unstable:%lu\n"
> +		" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
>  		" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
> -		" free_cma:%lu\n",
> +		" free:%lu free_pcp:%lu free_cma:%lu\n",
>  		global_page_state(NR_ACTIVE_ANON),
>  		global_page_state(NR_INACTIVE_ANON),
>  		global_page_state(NR_ISOLATED_ANON),
> @@ -3235,13 +3243,14 @@ void show_free_areas(unsigned int filter)
>  		global_page_state(NR_FILE_DIRTY),
>  		global_page_state(NR_WRITEBACK),
>  		global_page_state(NR_UNSTABLE_NFS),
> -		global_page_state(NR_FREE_PAGES),
>  		global_page_state(NR_SLAB_RECLAIMABLE),
>  		global_page_state(NR_SLAB_UNRECLAIMABLE),
>  		global_page_state(NR_FILE_MAPPED),
>  		global_page_state(NR_SHMEM),
>  		global_page_state(NR_PAGETABLE),
>  		global_page_state(NR_BOUNCE),
> +		global_page_state(NR_FREE_PAGES),
> +		free_pcp,
>  		global_page_state(NR_FREE_CMA_PAGES));
>  
>  	for_each_populated_zone(zone) {
> @@ -3249,6 +3258,11 @@ void show_free_areas(unsigned int filter)
>  
>  		if (skip_free_areas_node(filter, zone_to_nid(zone)))
>  			continue;
> +
> +		free_pcp = 0;
> +		for_each_online_cpu(cpu)
> +			free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;
> +
>  		show_node(zone);
>  		printk("%s"
>  			" free:%lukB"
> @@ -3275,6 +3289,8 @@ void show_free_areas(unsigned int filter)
>  			" pagetables:%lukB"
>  			" unstable:%lukB"
>  			" bounce:%lukB"
> +			" free_pcp:%lukB"
> +			" local_pcp:%ukB"
>  			" free_cma:%lukB"
>  			" writeback_tmp:%lukB"
>  			" pages_scanned:%lu"
> @@ -3306,6 +3322,8 @@ void show_free_areas(unsigned int filter)
>  			K(zone_page_state(zone, NR_PAGETABLE)),
>  			K(zone_page_state(zone, NR_UNSTABLE_NFS)),
>  			K(zone_page_state(zone, NR_BOUNCE)),
> +			K(free_pcp),
> +			K(this_cpu_read(zone->pageset->pcp.count)),
>  			K(zone_page_state(zone, NR_FREE_CMA_PAGES)),
>  			K(zone_page_state(zone, NR_WRITEBACK_TEMP)),
>  			K(zone_page_state(zone, NR_PAGES_SCANNED)),
> 
> --
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-- 
Michal Hocko
SUSE Labs
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