From: Michal Hocko <mhocko@suse.com>
To: Feng Tang <feng.tang@intel.com>
Cc: David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@techsingularity.net>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] mm/page_alloc: detect allocation forbidden by cpuset and bail out early
Date: Wed, 15 Sep 2021 13:30:27 +0200 [thread overview]
Message-ID: <YUHZU4OHaJy3WtRk@dhcp22.suse.cz> (raw)
In-Reply-To: <20210915053247.GG56674@shbuild999.sh.intel.com>
On Wed 15-09-21 13:32:47, Feng Tang wrote:
> On Tue, Sep 14, 2021 at 05:30:03PM -0700, David Rientjes wrote:
[...]
> > I'm wondering about a single node nodemask, for example, where all
> > ZONE_NORMAL memory is hot-removed.
While this is theoretically possible it is highly unlikely to happen.
Non movable memory just takes one kernel allocation to prevent any
hotremove operation to finish. I have to say I was not aware of the
hotplug callback. It all seems rather suspicious. I will have a look.
Anyway something worth having covered "just in case". Thanks for
pointing it out.
> Thanks for the reminding! Yes, memory hot remove can change the
> cpuset's effective nodemask, we may need to add similar check inside
> cpuset_hotplug_update_tasks() which is called by cpuset_hotplug_workfn(),
> something like below?
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 7fa633e..d5f6776 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3186,6 +3186,14 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
> cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
> mems_updated = !nodes_equal(new_mems, cs->effective_mems);
>
> + if (mems_updated && !cpusets_insane_config() &&
> + movable_only_nodes(new_mems)) {
> + static_branch_enable(&cpusets_insane_config_key);
> + pr_info("Unsupported (movable nodes only) cpuset configuration detected (nmask=%*pbl) after memory hotplug."
> + "Cpuset allocations might fail even with a lot of memory available.\n",
> + nodemask_pr_args(new_mems);
> + }
Please create a helper rather than two copies of the same. Thanks!
> +
> if (is_in_v2_mode())
> hotplug_update_tasks(cs, &new_cpus, &new_mems,
> cpus_updated, mems_updated);
>
> Thanks,
> Feng
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-09-15 11:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-14 3:40 [PATCH v3] mm/page_alloc: detect allocation forbidden by cpuset and bail out early Feng Tang
2021-09-14 8:01 ` Vlastimil Babka
2021-09-14 8:17 ` Michal Hocko
2021-09-14 8:50 ` Michal Hocko
2021-09-24 6:10 ` Feng Tang
2021-09-24 7:17 ` Michal Hocko
2021-09-15 0:30 ` David Rientjes
2021-09-15 5:32 ` Feng Tang
2021-09-15 11:30 ` Michal Hocko [this message]
2021-09-16 8:11 ` Feng Tang
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