linux-kernel - Re: [PATCH -mm 0/6] memcg: release memcg_cache

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Date:	Wed, 23 Jul 2014 14:53:12 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	<akpm@...ux-foundation.org>
CC:	<mhocko@...e.cz>, <hannes@...xchg.org>, <cl@...ux.com>,
	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm 0/6] memcg: release memcg_cache_id on css offline

On Mon, Jul 21, 2014 at 03:47:10PM +0400, Vladimir Davydov wrote:
> This patch set makes memcg release memcg_cache_id on css offline. This
> way the memcg_caches arrays size will be limited by the number of alive
> kmem-active memory cgroups, which is much better.

Hi Andrew,

While preparing the per-memcg slab shrinkers patch set, I realized that
releasing memcg_cache_id on css offline is incorrect, because after css
offline there still can be elements on per-memcg list_lrus, which are
indexed by memcg_cache_id. We could re-parent them, but this is what we
decided to avoid in order to keep things clean and simple. So it seems
there's nothing we can do except keeping memcg_cache_ids till css free.

I wonder if we could reclaim memory from per memcg arrays (per memcg
list_lrus, kmem_caches) on memory pressure. May be, we could use
flex_array to achieve that.

Anyway, could you please drop the following patches from the mmotm tree
(all this set except patch 1, which is a mere cleanup)?

  memcg-release-memcg_cache_id-on-css-offline
  memcg-keep-all-children-of-each-root-cache-on-a-list
  memcg-add-pointer-to-owner-cache-to-memcg_cache_params
  memcg-make-memcg_cache_id-static
  slab-use-mem_cgroup_id-for-per-memcg-cache-naming

Sorry about the noise.

Thank you.
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