linux-kernel - Re: [PATCH] memcg: page_alloc: skip bulk allocator for __GFP

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Message-ID: <4c92e227-2abc-c3cb-93eb-f5c45bef7fc6@virtuozzo.com>
Date:   Thu, 14 Oct 2021 10:05:21 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Cc:     Uladzislau Rezki <urezki@...il.com>, Roman Gushchin <guro@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg: page_alloc: skip bulk allocator for __GFP_ACCOUNT

On 13.10.2021 22:43, Shakeel Butt wrote:
> The commit 5c1f4e690eec ("mm/vmalloc: switch to bulk allocator in
> __vmalloc_area_node()") switched to bulk page allocator for order 0
> allocation backing vmalloc. However bulk page allocator does not support
> __GFP_ACCOUNT allocations and there are several users of
> kvmalloc(__GFP_ACCOUNT).
> 
> For now make __GFP_ACCOUNT allocations bypass bulk page allocator. In
> future if there is workload that can be significantly improved with the
> bulk page allocator with __GFP_ACCCOUNT support, we can revisit the
> decision.
> 
> Fixes: 5c1f4e690eec ("mm/vmalloc: switch to bulk allocator in __vmalloc_area_node()")
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
> ---
>  mm/page_alloc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 668edb16446a..b3acad4615d3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5215,6 +5215,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
>  	unsigned int alloc_flags = ALLOC_WMARK_LOW;
>  	int nr_populated = 0, nr_account = 0;
>  
> +	/* Bulk allocator does not support memcg accounting. */
> +	if (unlikely(gfp & __GFP_ACCOUNT))
> +		goto out;
> +

May be (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT)) check is better here?

>  	/*
>  	 * Skip populated array elements to determine if any pages need
>  	 * to be allocated before disabling IRQs.
>