From: Frederic Weisbecker <frederic@kernel.org>
To: "Leonardo Brás" <leobras@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Marcelo Tosatti <mtosatti@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeelb@google.com>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbecker@suse.de>
Subject: Re: [PATCH v2 0/5] Introduce memcg_stock_pcp remote draining
Date: Fri, 27 Jan 2023 14:03:59 +0100 [thread overview]
Message-ID: <Y9PLvzI8WU0vYWUt@lothringen> (raw)
In-Reply-To: <601fc35a8cc2167e53e45c636fccb2d899fd7c50.camel@redhat.com>
On Fri, Jan 27, 2023 at 05:12:13AM -0300, Leonardo Brás wrote:
> On Fri, 2023-01-27 at 04:22 -0300, Leonardo Brás wrote:
> > > Hmm, OK, I have misunderstood your proposal. Yes, the overal pcp charges
> > > potentially left behind should be small and that shouldn't really be a
> > > concern for memcg oom situations (unless the limit is very small and
> > > workloads on isolated cpus using small hard limits is way beyond my
> > > imagination).
> > >
> > > My first thought was that those charges could be left behind without any
> > > upper bound but in reality sooner or later something should be running
> > > on those cpus and if the memcg is gone the pcp cache would get refilled
> > > and old charges gone.
> > >
> > > So yes, this is actually a better and even simpler solution. All we need
> > > is something like this
> > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > > index ab457f0394ab..13b84bbd70ba 100644
> > > --- a/mm/memcontrol.c
> > > +++ b/mm/memcontrol.c
> > > @@ -2344,6 +2344,9 @@ static void drain_all_stock(struct mem_cgroup *root_memcg)
> > > struct mem_cgroup *memcg;
> > > bool flush = false;
> > >
> > > + if (cpu_is_isolated(cpu))
> > > + continue;
> > > +
> > > rcu_read_lock();
> > > memcg = stock->cached;
> > > if (memcg && stock->nr_pages &&
> > >
> > > There is no such cpu_is_isolated() AFAICS so we would need a help from
> > > NOHZ and cpuisol people to create one for us. Frederic, would such an
> > > abstraction make any sense from your POV?
> >
> >
> > IIUC, 'if (cpu_is_isolated())' would be instead:
> >
> > if (!housekeeping_cpu(smp_processor_id(), HK_TYPE_DOMAIN) ||
> > !housekeeping_cpu(smp_processor_id(), HK_TYPE_WQ)
>
> oh, sorry 's/smp_processor_id()/cpu/' here:
>
> if(!housekeeping_cpu(cpu, HK_TYPE_DOMAIN) || !housekeeping_cpu(cpu, HK_TYPE_WQ))
Do you also need to handle cpuset.sched_load_balance=0 (aka. cpuset v2 "isolated"
partition type). It has the same effect as isolcpus=, but it can be changed at
runtime.
And then on_null_domain() look like what you need. You'd have to make that API
more generally available though, and rename it to something like
"bool cpu_has_null_domain(int cpu)".
But then you also need to handle concurrent cpuset changes. If you can tolerate
it to be racy, then RCU alone is fine.
Thanks.
next prev parent reply other threads:[~2023-01-27 13:04 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 7:34 [PATCH v2 0/5] Introduce memcg_stock_pcp remote draining Leonardo Bras
2023-01-25 7:34 ` [PATCH v2 1/5] mm/memcontrol: Align percpu memcg_stock to cache Leonardo Bras
2023-01-25 7:34 ` [PATCH v2 2/5] mm/memcontrol: Change stock_lock type from local_lock_t to spinlock_t Leonardo Bras
2023-01-25 7:35 ` [PATCH v2 3/5] mm/memcontrol: Reorder memcg_stock_pcp members to avoid holes Leonardo Bras
2023-01-25 7:35 ` [PATCH v2 4/5] mm/memcontrol: Perform all stock drain in current CPU Leonardo Bras
2023-01-25 7:35 ` [PATCH v2 5/5] mm/memcontrol: Remove flags from memcg_stock_pcp Leonardo Bras
2023-01-25 8:33 ` [PATCH v2 0/5] Introduce memcg_stock_pcp remote draining Michal Hocko
2023-01-25 11:06 ` Leonardo Brás
2023-01-25 11:39 ` Michal Hocko
2023-01-25 18:22 ` Marcelo Tosatti
2023-01-25 23:14 ` Roman Gushchin
2023-01-26 7:41 ` Michal Hocko
2023-01-26 18:03 ` Marcelo Tosatti
2023-01-26 19:20 ` Michal Hocko
2023-01-27 0:32 ` Marcelo Tosatti
2023-01-27 6:58 ` Michal Hocko
2023-02-01 18:31 ` Roman Gushchin
2023-01-26 23:12 ` Roman Gushchin
2023-01-27 7:11 ` Michal Hocko
2023-01-27 7:22 ` Leonardo Brás
2023-01-27 8:12 ` Leonardo Brás
2023-01-27 9:23 ` Michal Hocko
2023-01-27 13:03 ` Frederic Weisbecker [this message]
2023-01-27 13:58 ` Michal Hocko
2023-01-27 18:18 ` Roman Gushchin
2023-02-03 15:21 ` Michal Hocko
2023-02-03 19:25 ` Roman Gushchin
2023-02-13 13:36 ` Michal Hocko
2023-01-27 7:14 ` Leonardo Brás
2023-01-27 7:20 ` Michal Hocko
2023-01-27 7:35 ` Leonardo Brás
2023-01-27 9:29 ` Michal Hocko
2023-01-27 19:29 ` Leonardo Brás
2023-01-27 23:50 ` Roman Gushchin
2023-01-26 18:19 ` Marcelo Tosatti
2023-01-27 5:40 ` Leonardo Brás
2023-01-26 7:45 ` Michal Hocko
2023-01-26 18:14 ` Marcelo Tosatti
2023-01-26 19:13 ` Michal Hocko
2023-01-27 6:55 ` Leonardo Brás
2023-01-31 11:35 ` Marcelo Tosatti
2023-02-01 4:36 ` Leonardo Brás
2023-02-01 12:52 ` Michal Hocko
2023-02-01 12:41 ` Michal Hocko
2023-02-04 4:55 ` Leonardo Brás
2023-02-05 19:49 ` Roman Gushchin
2023-02-07 3:18 ` Leonardo Brás
2023-02-08 19:23 ` Roman Gushchin
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