From: Peter Zijlstra <peterz@infradead.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com
Subject: Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads
Date: Sat, 29 Jul 2017 11:10:55 +0200 [thread overview]
Message-ID: <20170729091055.GA6524@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20170727153010.23347-4-hannes@cmpxchg.org>
So no, this doesn't have a change in hell of making it.
On Thu, Jul 27, 2017 at 11:30:10AM -0400, Johannes Weiner wrote:
> +static void domain_cpu_update(struct memdelay_domain *md, int cpu,
> + int old, int new)
> +{
> + enum memdelay_domain_state state;
> + struct memdelay_domain_cpu *mdc;
> + unsigned long now, delta;
> + unsigned long flags;
> +
> + mdc = per_cpu_ptr(md->mdcs, cpu);
> + spin_lock_irqsave(&mdc->lock, flags);
Afaict this is inside scheduler locks, this cannot be a spinlock. Also,
do we really want to add more atomics there?
> + if (old) {
> + WARN_ONCE(!mdc->tasks[old], "cpu=%d old=%d new=%d counter=%d\n",
> + cpu, old, new, mdc->tasks[old]);
> + mdc->tasks[old] -= 1;
> + }
> + if (new)
> + mdc->tasks[new] += 1;
> +
> + /*
> + * The domain is somewhat delayed when a number of tasks are
> + * delayed but there are still others running the workload.
> + *
> + * The domain is fully delayed when all non-idle tasks on the
> + * CPU are delayed, or when a delayed task is actively running
> + * and preventing productive tasks from making headway.
> + *
> + * The state times then add up over all CPUs in the domain: if
> + * the domain is fully blocked on one CPU and there is another
> + * one running the workload, the domain is considered fully
> + * blocked 50% of the time.
> + */
> + if (!mdc->tasks[MTS_DELAYED_ACTIVE] && !mdc->tasks[MTS_DELAYED])
> + state = MDS_NONE;
> + else if (mdc->tasks[MTS_WORKING])
> + state = MDS_SOME;
> + else
> + state = MDS_FULL;
> +
> + if (mdc->state == state)
> + goto unlock;
> +
> + now = ktime_to_ns(ktime_get());
ktime_get_ns(), also no ktime in scheduler code.
> + delta = now - mdc->state_start;
> +
> + domain_move_clock(md);
> + md->times[mdc->state] += delta;
> +
> + mdc->state = state;
> + mdc->state_start = now;
> +unlock:
> + spin_unlock_irqrestore(&mdc->lock, flags);
> +}
> +
> +static struct memdelay_domain *memcg_domain(struct mem_cgroup *memcg)
> +{
> +#ifdef CONFIG_MEMCG
> + if (!mem_cgroup_disabled())
> + return memcg->memdelay_domain;
> +#endif
> + return &memdelay_global_domain;
> +}
> +
> +/**
> + * memdelay_task_change - note a task changing its delay/work state
> + * @task: the task changing state
> + * @delayed: 1 when task enters delayed state, -1 when it leaves
> + * @working: 1 when task enters working state, -1 when it leaves
> + * @active_delay: 1 when task enters active delay, -1 when it leaves
> + *
> + * Updates the task's domain counters to reflect a change in the
> + * task's delayed/working state.
> + */
> +void memdelay_task_change(struct task_struct *task, int old, int new)
> +{
> + int cpu = task_cpu(task);
> + struct mem_cgroup *memcg;
> + unsigned long delay = 0;
> +
> +#ifdef CONFIG_DEBUG_VM
> + WARN_ONCE(task->memdelay_state != old,
> + "cpu=%d task=%p state=%d (in_iowait=%d PF_MEMDELAYED=%d) old=%d new=%d\n",
> + cpu, task, task->memdelay_state, task->in_iowait,
> + !!(task->flags & PF_MEMDELAY), old, new);
> + task->memdelay_state = new;
> +#endif
> +
> + /* Account when tasks are entering and leaving delays */
> + if (old < MTS_DELAYED && new >= MTS_DELAYED) {
> + task->memdelay_start = ktime_to_ms(ktime_get());
> + } else if (old >= MTS_DELAYED && new < MTS_DELAYED) {
> + delay = ktime_to_ms(ktime_get()) - task->memdelay_start;
> + task->memdelay_total += delay;
> + }
Scheduler stuff will _NOT_ user ktime_get() and will _NOT_ do pointless
divisions into ms.
> +
> + /* Account domain state changes */
> + rcu_read_lock();
> + memcg = mem_cgroup_from_task(task);
> + do {
> + struct memdelay_domain *md;
> +
> + md = memcg_domain(memcg);
> + md->aggregate += delay;
> + domain_cpu_update(md, cpu, old, new);
> + } while (memcg && (memcg = parent_mem_cgroup(memcg)));
> + rcu_read_unlock();
We are _NOT_ going to do a 3rd cgroup iteration for every task action.
> +};
--
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next prev parent reply other threads:[~2017-07-29 9:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-27 15:30 [PATCH 0/3] memdelay: memory health metric for systems and workloads Johannes Weiner
2017-07-27 15:30 ` [PATCH 1/3] sched/loadavg: consolidate LOAD_INT, LOAD_FRAC macros Johannes Weiner
2017-07-27 15:30 ` [PATCH 2/3] mm: workingset: tell cache transitions from workingset thrashing Johannes Weiner
2017-07-27 15:30 ` [PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads Johannes Weiner
2017-07-27 15:56 ` Johannes Weiner
2017-07-29 9:10 ` Peter Zijlstra [this message]
2017-07-30 15:28 ` Johannes Weiner
2017-07-31 8:31 ` Peter Zijlstra
2017-07-31 18:41 ` Johannes Weiner
2017-07-31 19:49 ` Mike Galbraith
2017-07-31 20:38 ` Johannes Weiner
2017-08-01 2:23 ` Mike Galbraith
2017-08-01 7:57 ` Peter Zijlstra
2017-08-01 12:26 ` Johannes Weiner
2017-08-13 14:52 ` Peter Zijlstra
2017-07-29 13:31 ` kbuild test robot
2017-07-27 20:43 ` [PATCH 0/3] memdelay: memory health metric " Andrew Morton
2017-07-28 19:43 ` Johannes Weiner
2017-08-02 8:11 ` Michal Hocko
2017-07-29 2:48 ` Mike Galbraith
2017-07-29 3:21 ` Mike Galbraith
2017-07-29 6:38 ` Mike Galbraith
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