From: Michal Hocko <mhocko@kernel.org>
To: Hillf Danton <hdanton@sina.com>
Cc: linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Chris Down <chris@chrisdown.name>, Tejun Heo <tj@kernel.org>,
Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeelb@google.com>,
Matthew Wilcox <willy@infradead.org>,
Minchan Kim <minchan@kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: Re: [RFC v1] memcg: add memcg lru for page reclaiming
Date: Wed, 23 Oct 2019 10:08:23 +0200 [thread overview]
Message-ID: <20191023080823.GH754@dhcp22.suse.cz> (raw)
In-Reply-To: <20191023044448.16484-1-hdanton@sina.com>
On Wed 23-10-19 12:44:48, Hillf Danton wrote:
>
> On Tue, 22 Oct 2019 15:58:32 +0200 Michal Hocko wrote:
> >
> > On Tue 22-10-19 21:30:50, Hillf Danton wrote:
[...]
> > > in this RFC after ripping pages off
> > > the first victim, the work finishes with the first ancestor of the victim
> > > added to lru.
> > >
> > > Recaliming is defered until kswapd becomes active.
> >
> > This is a wrong assumption because high limit might be configured way
> > before kswapd is woken up.
>
> This change was introduced because high limit breach looks not like a
> serious problem in the absence of memory pressure. Lets do the hard work,
> reclaiming one memcg a time up through the hierarchy, when kswapd becomes
> active. It also explains the BH introduced.
But this goes against the main motivation for the high limit - to
throttle. It is not all that important that there is not global memory
pressure. The preventive high limit reclaim is there to make sure that
the specific memcg is kept in a reasonable containment.
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2019-10-23 8:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191021115654.14740-1-hdanton@sina.com>
2019-10-21 12:14 ` [RFC v1] memcg: add memcg lru for page reclaiming Michal Hocko
[not found] ` <20191022133050.15620-1-hdanton@sina.com>
2019-10-22 13:58 ` Michal Hocko
[not found] ` <20191023044448.16484-1-hdanton@sina.com>
2019-10-23 8:08 ` Michal Hocko [this message]
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