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Date:   Mon, 25 Jan 2021 17:54:51 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
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Subject: Re: [PATCH v16 08/11] secretmem: add memcg accounting
Message-ID: <20210125165451.GT827@dhcp22.suse.cz>
References: <20210121122723.3446-1-rppt@kernel.org>
 <20210121122723.3446-9-rppt@kernel.org>
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On Thu 21-01-21 14:27:20, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> Account memory consumed by secretmem to memcg. The accounting is updated
> when the memory is actually allocated and freed.

What does this mean? What are the lifetime rules?

[...]

> +static int secretmem_account_pages(struct page *page, gfp_t gfp, int order)
> +{
> +	int err;
> +
> +	err = memcg_kmem_charge_page(page, gfp, order);
> +	if (err)
> +		return err;
> +
> +	/*
> +	 * seceremem caches are unreclaimable kernel allocations, so treat
> +	 * them as unreclaimable slab memory for VM statistics purposes
> +	 */
> +	mod_lruvec_page_state(page, NR_SLAB_UNRECLAIMABLE_B,
> +			      PAGE_SIZE << order);

A lot of memcg accounted memory is not reclaimable. Why do you abuse
SLAB counter when this is not a slab owned memory? Why do you use the
kmem accounting API when __GFP_ACCOUNT should give you the same without
this details?
-- 
Michal Hocko
SUSE Labs