Re: [PATCH RFC] mm, proc: add PcpFree to meminfo

[Kefeng Wang]

On 2022/8/16 16:44, Kefeng Wang wrote:
> From: Liu Shixin <liushixin2@xxxxxxxxxx>
>
> The page on pcplist could be used, but not counted into memory free or
> avaliable, and pcp_free is only showed by show_mem(). Since commit
> d8a759b57035 ("mm, page_alloc: double zone's batchsize"), there is a
> significant decrease in the display of free memory, with a large number
> of cpus and nodes, the number of pages in the percpu list can be very
> large, so it is better to let user to know the pcp count.
Add more experts according to commit d8a759b57035，
any advice would be much appreciated，thanks.
> Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> ---
>   drivers/base/node.c | 14 +++++++++++++-
>   fs/proc/meminfo.c   |  9 +++++++++
>   2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index eb0f43784c2b..846864e45db6 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -375,6 +375,9 @@ static ssize_t node_read_meminfo(struct device *dev,
>   	struct sysinfo i;
>   	unsigned long sreclaimable, sunreclaimable;
>   	unsigned long swapcached = 0;
> +	unsigned long free_pcp = 0;
> +	struct zone *zone;
> +	int cpu;
>   
>   	si_meminfo_node(&i, nid);
>   	sreclaimable = node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B);
> @@ -382,9 +385,17 @@ static ssize_t node_read_meminfo(struct device *dev,
>   #ifdef CONFIG_SWAP
>   	swapcached = node_page_state_pages(pgdat, NR_SWAPCACHE);
>   #endif
> +	for_each_populated_zone(zone) {
> +		if (zone_to_nid(zone) != nid)
> +			continue;
> +		for_each_online_cpu(cpu)
> +			free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
> +	}
> +
>   	len = sysfs_emit_at(buf, len,
>   			    "Node %d MemTotal:       %8lu kB\n"
>   			    "Node %d MemFree:        %8lu kB\n"
> +			    "Node %d PcpFree:        %8lu kB\n"
>   			    "Node %d MemUsed:        %8lu kB\n"
>   			    "Node %d SwapCached:     %8lu kB\n"
>   			    "Node %d Active:         %8lu kB\n"
> @@ -397,7 +408,8 @@ static ssize_t node_read_meminfo(struct device *dev,
>   			    "Node %d Mlocked:        %8lu kB\n",
>   			    nid, K(i.totalram),
>   			    nid, K(i.freeram),
> -			    nid, K(i.totalram - i.freeram),
> +			    nid, K(free_pcp),
> +			    nid, K(i.totalram - i.freeram - free_pcp),
>   			    nid, K(swapcached),
>   			    nid, K(node_page_state(pgdat, NR_ACTIVE_ANON) +
>   				   node_page_state(pgdat, NR_ACTIVE_FILE)),
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 6e89f0e2fd20..672c784dfc8a 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -38,6 +38,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>   	unsigned long pages[NR_LRU_LISTS];
>   	unsigned long sreclaimable, sunreclaim;
>   	int lru;
> +	unsigned long free_pcp = 0;
> +	struct zone *zone;
> +	int cpu;
>   
>   	si_meminfo(&i);
>   	si_swapinfo(&i);
> @@ -55,8 +58,14 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>   	sreclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B);
>   	sunreclaim = global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B);
>   
> +	for_each_populated_zone(zone) {
> +		for_each_online_cpu(cpu)
> +			free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
> +	}
> +
>   	show_val_kb(m, "MemTotal:       ", i.totalram);
>   	show_val_kb(m, "MemFree:        ", i.freeram);
> +	show_val_kb(m, "PcpFree:        ", free_pcp);
>   	show_val_kb(m, "MemAvailable:   ", available);
>   	show_val_kb(m, "Buffers:        ", i.bufferram);
>   	show_val_kb(m, "Cached:         ", cached);