linux-kernel - Re: [PATCH v2] memcg: add per-memcg vmalloc stat

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Message-ID: <YcPYz4N0sXEVFaJA@carbon.dhcp.thefacebook.com>
Date:   Wed, 22 Dec 2021 18:02:55 -0800
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] memcg: add per-memcg vmalloc stat

On Tue, Dec 21, 2021 at 09:24:57PM -0800, Shakeel Butt wrote:
> The kvmalloc* allocation functions can fallback to vmalloc allocations
> and more often on long running machines. In addition the kernel does
> have __GFP_ACCOUNT kvmalloc* calls. So, often on long running machines,
> the memory.stat does not tell the complete picture which type of memory
> is charged to the memcg. So add a per-memcg vmalloc stat.
> 
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
> 
> ---
> Changelog since v1:
> - page_memcg() within rcu lock as suggested by Muchun.
> 
>  Documentation/admin-guide/cgroup-v2.rst |  3 +++
>  include/linux/memcontrol.h              | 21 +++++++++++++++++++++
>  mm/memcontrol.c                         |  1 +
>  mm/vmalloc.c                            |  5 +++++
>  4 files changed, 30 insertions(+)
> 
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index 82c8dc91b2be..5aa368d165da 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -1314,6 +1314,9 @@ PAGE_SIZE multiple when read back.
>  	  sock (npn)
>  		Amount of memory used in network transmission buffers
>  
> +	  vmalloc (npn)
> +		Amount of memory used for vmap backed memory.
> +

It's a bid sad that this counter will partially intersect with others
(e.g. percpu and stack), but I don't see how it can be easily fixed.

But I agree that the counter is useful and worth adding.

Acked-by: Roman Gushchin <guro@...com>

Thanks!