linux-kernel - Re: [PATCH v6 06/29] memcg: kmem controller infrastructure

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Message-ID: <0000013abd91e573-0ea881ef-538b-40dd-8056-9532812eb165-000000@email.amazonses.com>
Date:	Thu, 1 Nov 2012 20:03:06 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	kamezawa.hiroyu@...fujitsu.com,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH v6 06/29] memcg: kmem controller infrastructure

On Thu, 1 Nov 2012, Glauber Costa wrote:

> +#ifdef CONFIG_MEMCG_KMEM
> +static inline bool memcg_kmem_enabled(void)
> +{
> +	return true;
> +}
> +

Maybe it would be better to do this in the same way that NUMA_BUILD was
done in kernel.h?


> +static __always_inline bool
> +memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **memcg, int order)
> +{
> +	if (!memcg_kmem_enabled())
> +		return true;
> +
> +	/*
> +	 * __GFP_NOFAIL allocations will move on even if charging is not
> +	 * possible. Therefore we don't even try, and have this allocation
> +	 * unaccounted. We could in theory charge it with
> +	 * res_counter_charge_nofail, but we hope those allocations are rare,
> +	 * and won't be worth the trouble.
> +	 */
> +	if (!(gfp & __GFP_KMEMCG) || (gfp & __GFP_NOFAIL))
> +		return true;


> +	if (in_interrupt() || (!current->mm) || (current->flags & PF_KTHREAD))
> +		return true;

This type of check is repeatedly occurring in various subsystems. Could we
get a function (maybe inline) to do this check?

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