linux-kernel - Re: [PATCH RFC v1 0/2] mm, pcp: add high order page info in /proc/zoneinfo

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Message-ID: <3550dfef-af8c-b76c-4f4d-6ec790864359@google.com>
Date: Mon, 15 Jan 2024 12:32:05 -0800 (PST)
From: David Rientjes <rientjes@...gle.com>
To: Vern Hao <haoxing990@...il.com>
cc: mgorman@...hsingularity.net, akpm@...ux-foundation.org, linux-mm@...ck.org, 
    linux-kernel@...r.kernel.org, Xin Hao <vernhao@...cent.com>
Subject: Re: [PATCH RFC v1 0/2] mm, pcp: add high order page info in
 /proc/zoneinfo

On Mon, 15 Jan 2024, Vern Hao wrote:

> From: Xin Hao <vernhao@...cent.com>
> 
> With /proc/zoneinfo we can simply get the number of pages used each cpu,
> but we can't get more detailed information about the distribution of
> those pages, such as the count of high order pages, through these
> patches, we can know the usage of each order page in detail, which will
> be helpful for us to analyze the pcp memory usage of application on the
> related cpus.
> 

Could you elaborate on the use case for this?

I'm not exactly sure what is meant by analyzing the pcp memory usage of an 
application; this would be a property of page allocations and freeing on 
individual cpus for orders that have pcp lists.  That's traditionally not 
a property of an individual application.

> By the way, on my intel 32 cores machine, i found that the 'struct
> per_cpu_pages' size increases 64 bytes, it seems like a bad news,
> i did some tests like stress-ng, but it did not see any performance
> degradation, and maybe use 'pcp->list' is also a possible way to get
> high order pages count, but it will increase the /proc/zoneinfo query
> time, so any meaningful suggestions are welcome!
> 
> Xin Hao (2):
>   mm, pcp: rename pcp->count to pcp->total_count
>   mm, pcp: add more detail info about high order page count
> 
>  include/linux/mmzone.h |  3 ++-
>  mm/page_alloc.c        | 46 +++++++++++++++++++++++-------------------
>  mm/show_mem.c          |  6 +++---
>  mm/vmstat.c            | 22 ++++++++++++--------
>  4 files changed, 44 insertions(+), 33 deletions(-)
> 
> -- 
> 2.31.1
> 
> 
>