From: Johannes Weiner <hannes@cmpxchg.org>
To: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] radix-tree: account nodes to memcg only if explicitly requested
Date: Mon, 1 Aug 2016 13:14:35 -0400 [thread overview]
Message-ID: <20160801171435.GA8724@cmpxchg.org> (raw)
In-Reply-To: <20160801160605.GA13263@esperanza>
On Mon, Aug 01, 2016 at 07:06:05PM +0300, Vladimir Davydov wrote:
> On Mon, Aug 01, 2016 at 11:24:09AM -0400, Johannes Weiner wrote:
> > On Mon, Aug 01, 2016 at 04:13:08PM +0300, Vladimir Davydov wrote:
> > > @@ -351,6 +351,12 @@ static int __radix_tree_preload(gfp_t gfp_mask, int nr)
> > > struct radix_tree_node *node;
> > > int ret = -ENOMEM;
> > >
> > > + /*
> > > + * Nodes preloaded by one cgroup can be be used by another cgroup, so
> > > + * they should never be accounted to any particular memory cgroup.
> > > + */
> > > + gfp_mask &= ~__GFP_ACCOUNT;
> >
> > But *all* page cache radix tree nodes are allocated from inside the
> > preload code, since the tree insertions need mapping->tree_lock. So
> > this would effectively disable accounting of the biggest radix tree
> > consumer in the kernel, no?
>
> No, that's not how accounting of radix tree nodes works. We never
> account preloaded nodes, because this could result in a node accounted
> to one cgroup used by an unrelated cgroup. Instead we always try to
> kmalloc a node on insertion falling back on preloads only if kmalloc
> fails - see commit 58e698af4c634 ("radix-tree: account radix_tree_node
> to memory cgroup").
You are right, I forgot we are doing this. The patch makes sense then.
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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next prev parent reply other threads:[~2016-08-01 17:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-01 13:13 Vladimir Davydov
2016-08-01 15:24 ` Johannes Weiner
2016-08-01 16:06 ` Vladimir Davydov
2016-08-01 17:14 ` Johannes Weiner [this message]
2016-08-02 11:51 ` Michal Hocko
2016-08-02 12:42 ` Vladimir Davydov
2016-08-02 12:46 ` Michal Hocko
2016-08-02 18:51 ` Andrew Morton
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