linux-kernel - Re: memcg memory accounting in vmalloc is broken

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Date:   Thu, 7 Oct 2021 16:00:21 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Vasily Averin <vvs@...tuozzo.com>, Michal Hocko <mhocko@...e.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Cgroups <cgroups@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel@...nvz.org, Mel Gorman <mgorman@...e.de>,
        Uladzislau Rezki <urezki@...il.com>
Subject: Re: memcg memory accounting in vmalloc is broken

On 10/7/21 10:50, Vasily Averin wrote:
> On 10/7/21 11:16 AM, Michal Hocko wrote:
>> Cc Mel and Uladzislau
>> 
>> On Thu 07-10-21 10:13:23, Michal Hocko wrote:
>>> On Thu 07-10-21 11:04:40, Vasily Averin wrote:
>>>> vmalloc was switched to __alloc_pages_bulk but it does not account the memory to memcg.
>>>>
>>>> Is it known issue perhaps?
>>>
>>> No, I think this was just overlooked. Definitely doesn't look
>>> intentional to me.
> 
> I use following patch as a quick fix,
> it helps though it is far from ideal and can be optimized.
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index b37435c274cf..e6abe2cac159 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5290,6 +5290,12 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
>  
>  		page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags,
>  								pcp, pcp_list);
> +
> +		if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT) && page &&
> +		    unlikely(__memcg_kmem_charge_page(page, gfp, 0) != 0)) {
> +			__free_pages(page, 0);

It's too early for this here, we didn't go through prep_new_page() yet,
minimally the post_alloc_hook() -> set_page_refcounted() part, required for
put_page_testzero() in __free_pages() to work properly, and probably other
stuff.
Either do the full prep+free or a minimal reversion of  __rmqueue_pcplist -
something to just put the page back to pcplist. Probably the former so we
don't introduce subtle errors.

> +			page = NULL;
> +		}
>  		if (unlikely(!page)) {
>  			/* Try and get at least one page */
>  			if (!nr_populated)
>