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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Aug 16, 2022 at 04:44:26PM +0800, Kefeng Wang wrote:
> From: Liu Shixin <liushixin2@huawei.com>
> 
> 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.
> 
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  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"

First off, this sysfs file is a huge violation of the normal sysfs
rules, so I will not allow any new entries to be added.  In fact, the
whole thing should just be removed and multiple files created in its
place.

Can you send a patch to do that instead please?

thanks,

greg k-h