linux-kernel - Re: [PATCH v2 6/6] zswap: memcg accounting

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Message-ID: <20220511173218.GB31592@blackbody.suse.cz>
Date:   Wed, 11 May 2022 19:32:18 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH v2 6/6] zswap: memcg accounting

Hello.

On Tue, May 10, 2022 at 11:28:47AM -0400, Johannes Weiner <hannes@...xchg.org> wrote:
> +void obj_cgroup_charge_zswap(struct obj_cgroup *objcg, size_t size)
> +{
> +	struct mem_cgroup *memcg;
> +
> +	VM_WARN_ON_ONCE(!(current->flags & PF_MEMALLOC));
> +
> +	/* PF_MEMALLOC context, charging must succeed */
> +	if (obj_cgroup_charge(objcg, GFP_KERNEL, size))
> +		VM_WARN_ON_ONCE(1);

IIUC, the objcg is derived from the compressed page, i.e. same memcg
(reparenting neglected for now). This memcg's memory.current is then
charged with the compressed object size.

Do I get it right that memory.zswap.current is a subset of memory.current?

(And that zswap is limited both by memory.max and memory.zswap.max?)

Thanks,
Michal