From: Roman Gushchin <guro@fb.com>
To: Chris Down <chris@chrisdown.name>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>, Tejun Heo <tj@kernel.org>,
Dennis Zhou <dennis@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH] mm: Proportional memory.{low,min} reclaim
Date: Mon, 28 Jan 2019 21:52:40 +0000 [thread overview]
Message-ID: <20190128215230.GA32069@castle.DHCP.thefacebook.com> (raw)
In-Reply-To: <20190128214213.GB15349@chrisdown.name>
On Mon, Jan 28, 2019 at 04:42:13PM -0500, Chris Down wrote:
> Roman Gushchin writes:
> > Hm, it looks a bit suspicious to me.
> >
> > Let's say memory.low = 3G, memory.min = 1G and memory.current = 2G.
> > cgroup_size / protection == 1, so scan doesn't depend on memory.min at all.
> >
> > So, we need to look directly at memory.emin in memcg_low_reclaim case, and
> > ignore memory.(e)low.
>
> Hmm, this isn't really a common situation that I'd thought about, but it
> seems reasonable to make the boundaries when in low reclaim to be between
> min and low, rather than 0 and low. I'll add another patch with that. Thanks
It's not a stopper, so I'm perfectly fine with a follow-up patch.
>
> > > + scan = clamp(scan, SWAP_CLUSTER_MAX, lruvec_size);
> >
> > Idk, how much sense does it have to make it larger than SWAP_CLUSTER_MAX,
> > given that it will become 0 on default (and almost any other) priority.
>
> In my testing, setting the scan target to 0 and thus reducing scope for
> reclaim can result in increasing the scan priority more than is desirable,
> and since we base some vm heuristics based on that, that seemed concerning.
>
> I'd rather start being a bit more cautious, erring on the side of scanning
> at least some pages from this memcg when priority gets elevated.
>
> Thanks for the review!
For the rest of the patch:
Reviewed-by: Roman Gushchin <guro@fb.com>
Thanks!
next prev parent reply other threads:[~2019-01-28 21:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-24 1:44 [PATCH] mm: Proportional memory.{low,min} reclaim Chris Down
2019-01-28 21:00 ` Roman Gushchin
2019-01-28 21:42 ` Chris Down
2019-01-28 21:52 ` Roman Gushchin [this message]
2019-07-15 22:35 ` Andrew Morton
2019-07-15 22:57 ` Chris Down
2019-07-16 17:24 ` Johannes Weiner
2019-09-26 11:49 ` Michal Hocko
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