From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH 5/6] cgroup/cpuset: Free DL BW in case can_attach() fails Date: Wed, 29 Mar 2023 10:31:15 -0400 Message-ID: References: <20230329125558.255239-1-juri.lelli@redhat.com> <20230329125558.255239-6-juri.lelli@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680100477; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Rg0hjjPhbd8bR4OyWVmG4r7qsayd0ZEyOdGiFaBs47s=; b=Nmphvaagz89Cdp6BCLC4igWdJMeDLqJl44XRVzJrCY5Nrv9oACwp73LeC/ACducgkxSmFE wsgI2URzlk5kPrjy7NmAB2GGHwPY1K2QSTsrbwtx1keybe6UjssZV9wVFzgcf8uY9mT0ye yWO4ptQkHKbneKundcqkHU1aeJDn+HQ= Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="utf-8"; format="flowed" To: Juri Lelli , Peter Zijlstra , Ingo Molnar , Qais Yousef , Tejun Heo , Zefan Li , Johannes Weiner , Hao Luo Cc: Dietmar Eggemann , Steven Rostedt , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, luca.abeni-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, claudio-YOzL5CV4y4YG1A2ADO40+w@public.gmane.org, tommaso.cucinotta-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mathieu.poirier-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Vincent Guittot , Wei Wang , Rick Yiu , Quentin Perret , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sudeep Holla On 3/29/23 10:25, Waiman Long wrote: > > On 3/29/23 08:55, Juri Lelli wrote: >> From: Dietmar Eggemann >> >> cpuset_can_attach() can fail. Postpone DL BW allocation until all tasks >> have been checked. DL BW is not allocated per-task but as a sum over >> all DL tasks migrating. >> >> If multiple controllers are attached to the cgroup next to the cuset > Typo: : "cuset" => "cpuset" >> controller a non-cpuset can_attach() can fail. In this case free DL BW >> in cpuset_cancel_attach(). >> >> Finally, update cpuset DL task count (nr_deadline_tasks) only in >> cpuset_attach(). >> >> Suggested-by: Waiman Long >> Signed-off-by: Dietmar Eggemann >> Signed-off-by: Juri Lelli >> --- >>   include/linux/sched.h  |  2 +- >>   kernel/cgroup/cpuset.c | 55 ++++++++++++++++++++++++++++++++++++++---- >>   kernel/sched/core.c    | 17 ++----------- >>   3 files changed, 53 insertions(+), 21 deletions(-) >> >> diff --git a/include/linux/sched.h b/include/linux/sched.h >> index 6f3d84e0ed08..50cbbfefbe11 100644 >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -1847,7 +1847,7 @@ current_restore_flags(unsigned long orig_flags, >> unsigned long flags) >>   } >>     extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, >> const struct cpumask *trial); >> -extern int task_can_attach(struct task_struct *p, const struct >> cpumask *cs_effective_cpus); >> +extern int task_can_attach(struct task_struct *p); >>   extern int dl_bw_alloc(int cpu, u64 dl_bw); >>   extern void dl_bw_free(int cpu, u64 dl_bw); >>   #ifdef CONFIG_SMP >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >> index eb0854ef9757..f8ebec66da51 100644 >> --- a/kernel/cgroup/cpuset.c >> +++ b/kernel/cgroup/cpuset.c >> @@ -198,6 +198,8 @@ struct cpuset { >>        * know when to rebuild associated root domain bandwidth >> information. >>        */ >>       int nr_deadline_tasks; >> +    int nr_migrate_dl_tasks; >> +    u64 sum_migrate_dl_bw; >>         /* Invalid partition error code, not lock protected */ >>       enum prs_errcode prs_err; >> @@ -2464,16 +2466,23 @@ static int fmeter_getrate(struct fmeter *fmp) >>     static struct cpuset *cpuset_attach_old_cs; >>   +static void reset_migrate_dl_data(struct cpuset *cs) >> +{ >> +    cs->nr_migrate_dl_tasks = 0; >> +    cs->sum_migrate_dl_bw = 0; >> +} >> + >>   /* Called by cgroups to determine if a cpuset is usable; >> cpuset_mutex held */ >>   static int cpuset_can_attach(struct cgroup_taskset *tset) >>   { >>       struct cgroup_subsys_state *css; >> -    struct cpuset *cs; >> +    struct cpuset *cs, *oldcs; >>       struct task_struct *task; >>       int ret; >>         /* used later by cpuset_attach() */ >>       cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css)); >> +    oldcs = cpuset_attach_old_cs; >>       cs = css_cs(css); >>         mutex_lock(&cpuset_mutex); >> @@ -2491,7 +2500,7 @@ static int cpuset_can_attach(struct >> cgroup_taskset *tset) >>           goto out_unlock; >>         cgroup_taskset_for_each(task, css, tset) { >> -        ret = task_can_attach(task, cs->effective_cpus); >> +        ret = task_can_attach(task); >>           if (ret) >>               goto out_unlock; >>           ret = security_task_setscheduler(task); >> @@ -2499,11 +2508,31 @@ static int cpuset_can_attach(struct >> cgroup_taskset *tset) >>               goto out_unlock; >>             if (dl_task(task)) { >> -            cs->nr_deadline_tasks++; >> -            cpuset_attach_old_cs->nr_deadline_tasks--; >> +            cs->nr_migrate_dl_tasks++; >> +            cs->sum_migrate_dl_bw += task->dl.dl_bw; >> +        } >> +    } >> + >> +    if (!cs->nr_migrate_dl_tasks) >> +        goto out_succes; >> + >> +    if (!cpumask_intersects(oldcs->effective_cpus, >> cs->effective_cpus)) { >> +        int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus); >> + >> +        if (unlikely(cpu >= nr_cpu_ids)) { >> +            reset_migrate_dl_data(cs); >> +            ret = -EINVAL; >> +            goto out_unlock; >> +        } >> + >> +        ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw); >> +        if (ret) { >> +            reset_migrate_dl_data(cs); >> +            goto out_unlock; >>           } >>       } >>   +out_succes: >>       /* >>        * Mark attach is in progress.  This makes validate_change() fail >>        * changes which zero cpus/mems_allowed. >> @@ -2518,11 +2547,21 @@ static int cpuset_can_attach(struct >> cgroup_taskset *tset) >>   static void cpuset_cancel_attach(struct cgroup_taskset *tset) >>   { >>       struct cgroup_subsys_state *css; >> +    struct cpuset *cs; >>         cgroup_taskset_first(tset, &css); >> +    cs = css_cs(css); >>         mutex_lock(&cpuset_mutex); >> -    css_cs(css)->attach_in_progress--; >> +    cs->attach_in_progress--; >> + >> +    if (cs->nr_migrate_dl_tasks) { >> +        int cpu = cpumask_any(cs->effective_cpus); >> + >> +        dl_bw_free(cpu, cs->sum_migrate_dl_bw); >> +        reset_migrate_dl_data(cs); >> +    } >> + Another nit that I have is that you may have to record also the cpu where the DL bandwidth is allocated in cpuset_can_attach() and free the bandwidth back into that cpu or there can be an underflow if another cpu is chosen. Cheers, Longman