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

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Date:   Thu, 18 Aug 2022 14:07:45 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mm@...ck.org, Aaron Lu <aaron.lu@...el.com>,
        Michal Hocko <mhocko@...e.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Kemi Wang <kemi.wang@...el.com>
Cc:     linux-kernel@...r.kernel.org, Liu Shixin <liushixin2@...wei.com>
Subject: Re: [PATCH RFC] mm, proc: add PcpFree to meminfo

On 8/17/22 00:16, Kefeng Wang wrote:
> On 2022/8/16 16:44, 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.
> Add more experts according to commit d8a759b57035，
> any advice would be much appreciated，thanks.

Adding a new meminfo field seems like overkill.  I'd just make this a
part of MemFree if anything.

Also, some actual data would be nice here.  Like:

	Before commit d8a759b57035, the maximum amount of pages in the
	pcp lists was theoretically $FOO MB.  After the patch, the lists
	can hold $BAR MB.  It has been observed to be $BAZ MB in
	practice.

	This was all on a system with $X memory NUMA nodes and $Y CPUs.