From: Reinette Chatre <reinette.chatre@intel.com>
To: James Morse <james.morse@arm.com>, <x86@kernel.org>,
<linux-kernel@vger.kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, Babu Moger <Babu.Moger@amd.com>,
<shameerali.kolothum.thodi@huawei.com>,
D Scott Phillips OS <scott@os.amperecomputing.com>,
<carl@os.amperecomputing.com>, <lcherian@marvell.com>,
<bobo.shaobowang@huawei.com>, <tan.shaopeng@fujitsu.com>,
<xingxin.hx@openanolis.org>, <baolin.wang@linux.alibaba.com>,
Jamie Iles <quic_jiles@quicinc.com>,
Xin Hao <xhao@linux.alibaba.com>, <peternewman@google.com>
Subject: Re: [PATCH v2 08/18] x86/resctrl: Queue mon_event_read() instead of sending an IPI
Date: Thu, 2 Feb 2023 15:47:58 -0800 [thread overview]
Message-ID: <b85cc905-3ea2-9f73-a592-0ebdc4240c37@intel.com> (raw)
In-Reply-To: <20230113175459.14825-9-james.morse@arm.com>
Hi James,
On 1/13/2023 9:54 AM, James Morse wrote:
> x86 is blessed with an abundance of monitors, one per RMID, that can be
> read from any CPU in the domain. MPAMs monitors reside in the MMIO MSC,
> the number implemented is up to the manufacturer. This means when there are
> fewer monitors than needed, they need to be allocated and freed.
>
> Worse, the domain may be broken up into slices, and the MMIO accesses
> for each slice may need performing from different CPUs.
>
> These two details mean MPAMs monitor code needs to be able to sleep, and
> IPI another CPU in the domain to read from a resource that has been sliced.
>
> mon_event_read() already invokes mon_event_count() via IPI, which means
> this isn't possible.
>
> Change mon_event_read() to schedule mon_event_count() on a remote CPU and
> wait, instead of sending an IPI. This function is only used in response to
> a user-space filesystem request (not the timing sensitive overflow code).
>
> This allows MPAM to hide the slice behaviour from resctrl, and to keep
> the monitor-allocation in monitor.c.
>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 7 +++++--
> arch/x86/kernel/cpu/resctrl/internal.h | 2 +-
> arch/x86/kernel/cpu/resctrl/monitor.c | 6 ++++--
> 3 files changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 1df0e3262bca..4ee3da6dced7 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -532,8 +532,11 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
> struct rdt_domain *d, struct rdtgroup *rdtgrp,
> int evtid, int first)
> {
> + /* When picking a cpu from cpu_mask, ensure it can't race with cpuhp */
Please consistently use CPU instead of cpu.
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> /*
> - * setup the parameters to send to the IPI to read the data.
> + * setup the parameters to pass to mon_event_count() to read the data.
> */
> rr->rgrp = rdtgrp;
> rr->evtid = evtid;
> @@ -542,7 +545,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
> rr->val = 0;
> rr->first = first;
>
> - smp_call_function_any(&d->cpu_mask, mon_event_count, rr, 1);
> + smp_call_on_cpu(cpumask_any(&d->cpu_mask), mon_event_count, rr, false);
This would be problematic for the use cases where single tasks are run on
adaptive-tick CPUs. If an adaptive-tick CPU is chosen to run the function then
it may never run. Real-time environments are target usage of resctrl (with examples
in the documentation).
Reinette
next prev parent reply other threads:[~2023-02-02 23:48 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-13 17:54 [PATCH v2 00/18] x86/resctrl: monitored closid+rmid together, separate arch/fs locking James Morse
2023-01-13 17:54 ` [PATCH v2 01/18] x86/resctrl: Track the closid with the rmid James Morse
2023-01-13 17:54 ` [PATCH v2 02/18] x86/resctrl: Access per-rmid structures by index James Morse
2023-01-17 18:28 ` Yu, Fenghua
2023-03-03 18:33 ` James Morse
2023-01-17 18:29 ` Yu, Fenghua
2023-02-02 23:44 ` Reinette Chatre
2023-03-03 18:33 ` James Morse
2023-01-13 17:54 ` [PATCH v2 03/18] x86/resctrl: Create helper for RMID allocation and mondata dir creation James Morse
2023-01-13 17:54 ` [PATCH v2 04/18] x86/resctrl: Move rmid allocation out of mkdir_rdt_prepare() James Morse
2023-01-17 18:28 ` Yu, Fenghua
2023-02-02 23:45 ` Reinette Chatre
2023-03-03 18:33 ` James Morse
2023-01-13 17:54 ` [PATCH v2 05/18] x86/resctrl: Allow RMID allocation to be scoped by CLOSID James Morse
2023-01-17 18:53 ` Yu, Fenghua
2023-03-03 18:34 ` James Morse
2023-02-02 23:45 ` Reinette Chatre
2023-03-03 18:34 ` James Morse
2023-03-10 19:57 ` Reinette Chatre
2023-01-13 17:54 ` [PATCH v2 06/18] x86/resctrl: Allow the allocator to check if a CLOSID can allocate clean RMID James Morse
2023-01-17 18:29 ` Yu, Fenghua
2023-03-03 18:35 ` James Morse
2023-02-02 23:46 ` Reinette Chatre
2023-03-03 18:36 ` James Morse
2023-03-10 19:59 ` Reinette Chatre
2023-03-20 17:12 ` James Morse
2023-01-13 17:54 ` [PATCH v2 07/18] x86/resctrl: Move CLOSID/RMID matching and setting to use helpers James Morse
2023-01-17 19:10 ` Yu, Fenghua
2023-03-03 18:37 ` James Morse
2023-02-02 23:47 ` Reinette Chatre
2023-03-06 11:32 ` James Morse
2023-03-08 10:30 ` Peter Newman
2023-03-10 20:00 ` Reinette Chatre
2023-01-13 17:54 ` [PATCH v2 08/18] x86/resctrl: Queue mon_event_read() instead of sending an IPI James Morse
2023-01-17 18:29 ` Yu, Fenghua
2023-03-06 11:32 ` James Morse
2023-03-10 20:00 ` Reinette Chatre
2023-02-02 23:47 ` Reinette Chatre [this message]
2023-03-06 11:33 ` James Morse
2023-03-08 16:09 ` James Morse
2023-03-10 20:06 ` Reinette Chatre
2023-03-20 17:12 ` James Morse
2023-01-13 17:54 ` [PATCH v2 09/18] x86/resctrl: Allow resctrl_arch_rmid_read() to sleep James Morse
2023-01-23 13:54 ` Peter Newman
2023-03-06 11:33 ` James Morse
2023-01-23 15:33 ` Peter Newman
2023-03-06 11:33 ` James Morse
2023-03-06 13:14 ` Peter Newman
2023-03-08 17:45 ` James Morse
2023-03-09 13:41 ` Peter Newman
2023-03-09 17:35 ` James Morse
2023-03-10 9:28 ` Peter Newman
2023-03-20 17:12 ` James Morse
2023-03-22 13:21 ` Peter Newman
2023-01-13 17:54 ` [PATCH v2 10/18] x86/resctrl: Allow arch to allocate memory needed in resctrl_arch_rmid_read() James Morse
2023-01-13 17:54 ` [PATCH v2 11/18] x86/resctrl: Make resctrl_mounted checks explicit James Morse
2023-01-13 17:54 ` [PATCH v2 12/18] x86/resctrl: Move alloc/mon static keys into helpers James Morse
2023-01-13 17:54 ` [PATCH v2 13/18] x86/resctrl: Make rdt_enable_key the arch's decision to switch James Morse
2023-02-02 23:48 ` Reinette Chatre
2023-01-13 17:54 ` [PATCH v2 14/18] x86/resctrl: Add helpers for system wide mon/alloc capable James Morse
2023-01-25 7:16 ` Shaopeng Tan (Fujitsu)
2023-03-06 11:34 ` James Morse
2023-01-13 17:54 ` [PATCH v2 15/18] x86/resctrl: Add cpu online callback for resctrl work James Morse
2023-01-13 17:54 ` [PATCH v2 16/18] x86/resctrl: Allow overflow/limbo handlers to be scheduled on any-but cpu James Morse
2023-02-02 23:49 ` Reinette Chatre
2023-03-06 11:34 ` James Morse
2023-01-13 17:54 ` [PATCH v2 17/18] x86/resctrl: Add cpu offline callback for resctrl work James Morse
2023-01-13 17:54 ` [PATCH v2 18/18] x86/resctrl: Separate arch and fs resctrl locks James Morse
2023-02-02 23:50 ` Reinette Chatre
2023-03-06 11:34 ` James Morse
2023-03-11 0:22 ` Reinette Chatre
2023-03-20 17:12 ` James Morse
2023-01-25 7:19 ` [PATCH v2 00/18] x86/resctrl: monitored closid+rmid together, separate arch/fs locking Shaopeng Tan (Fujitsu)
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