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

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Date:   Tue, 16 Aug 2022 18:11:18 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, Liu Shixin <liushixin2@...wei.com>
Subject: Re: [PATCH RFC] mm, proc: add PcpFree to meminfo


On 2022/8/16 17:16, Greg Kroah-Hartman wrote:
> On Tue, Aug 16, 2022 at 04:44:26PM +0800, Kefeng Wang wrote:
>> From: Liu Shixin <liushixin2@...wei.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@...wei.com>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.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.

Hi Greg, do you mean to remove all /sys/devices/system/node/node*/meminfo,

but this will beak ABI, is it acceptable?

>
> Can you send a patch to do that instead please?
>
> thanks,
>
> greg k-h
> .