Re: [RFC PATCH 00/13] Core scheduling v5

Ning, Hongyu
2020-05-09T03:39:51Z

- Test environment:
Intel Xeon Server platform
CPU(s): 192
On-line CPU(s) list: 0-191
Thread(s) per core: 2
Core(s) per socket: 48
Socket(s): 2
NUMA node(s): 4

- Kernel under test:
Core scheduling v5 base
https://github.com/digitalocean/linux-coresched/tree/coresched/v5-v5.5.y

- Test set based on sysbench 1.1.0-bd4b418:
A: sysbench cpu in cgroup cpu 1 + sysbench mysql in cgroup mysql 1 (192 workload tasks for each cgroup)
B: sysbench cpu in cgroup cpu 1 + sysbench cpu in cgroup cpu 2 + sysbench mysql in cgroup mysql 1 + sysbench mysql in cgroup mysql 2 (192 workload tasks for each cgroup)

- Test results briefing:
1 Good results:
1.1 For test set A, coresched could achieve same or better performance compared to smt_off, for both cpu workload and sysbench workload
1.2 For test set B, cpu workload, coresched could achieve better performance compared to smt_off

2 Bad results:
2.1 For test set B, mysql workload, coresched performance is lower than smt_off, potential fairness issue between cpu workloads and mysql workloads
2.2 For test set B, cpu workload, potential fairness issue between 2 cgroups cpu workloads

- Test results:
Note: test results in following tables are Tput normalized to default baseline

-- Test set A Tput normalized results:
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+
| | **** | default | coresched | smt_off | *** | default | coresched | smt_off |
+====================+========+===========+=============+===========+=======+=============+===============+=============+
| cgroups | **** | cg cpu 1 | cg cpu 1 | cg cpu 1 | *** | cg mysql 1 | cg mysql 1 | cg mysql 1 |
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+
| sysbench workload | **** | cpu | cpu | cpu | *** | mysql | mysql | mysql |
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+
| 192 tasks / cgroup | **** | 1 | 0.95 | 0.54 | *** | 1 | 0.92 | 0.97 |
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+

-- Test set B Tput normalized results:
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+------+-------------+---------------+-------------+-----+-------------+---------------+-------------+
| | **** | default | coresched | smt_off | *** | default | coresched | smt_off | ** | default | coresched | smt_off | * | default | coresched | smt_off |
+====================+========+===========+=============+===========+=======+=============+===============+=============+======+=============+===============+=============+=====+=============+===============+=============+
| cgroups | **** | cg cpu 1 | cg cpu 1 | cg cpu 1 | *** | cg cpu 2 | cg cpu 2 | cg cpu 2 | ** | cg mysql 1 | cg mysql 1 | cg mysql 1 | * | cg mysql 2 | cg mysql 2 | cg mysql 2 |
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+------+-------------+---------------+-------------+-----+-------------+---------------+-------------+
| sysbench workload | **** | cpu | cpu | cpu | *** | cpu | cpu | cpu | ** | mysql | mysql | mysql | * | mysql | mysql | mysql |
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+------+-------------+---------------+-------------+-----+-------------+---------------+-------------+
| 192 tasks / cgroup | **** | 1 | 0.9 | 0.47 | *** | 1 | 1.32 | 0.66 | ** | 1 | 0.42 | 0.89 | * | 1 | 0.42 | 0.89 |
+--------------------+--------+-----------+-------------+-----------+-------+-------------+---------------+-------------+------+-------------+---------------+-------------+-----+-------------+---------------+-------------+

> On Date: Wed, 4 Mar 2020 16:59:50 +0000, vpillai <vpillai@digitalocean.com> wrote:
> To: Nishanth Aravamudan <naravamudan@digitalocean.com>, Julien Desfossez <jdesfossez@digitalocean.com>, Peter Zijlstra <peterz@infradead.org>, Tim Chen <tim.c.chen@linux.intel.com>, mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org
> CC: vpillai <vpillai@digitalocean.com>, linux-kernel@vger.kernel.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld <pauld@redhat.com>, Aaron Lu <aaron.lwe@gmail.com>, Aubrey Li <aubrey.intel@gmail.com>, aubrey.li@linux.intel.com, Valentin Schneider <valentin.schneider@arm.com>, Mel Gorman <mgorman@techsingularity.net>, Pawan Gupta <pawan.kumar.gupta@linux.intel.com>, Paolo Bonzini <pbonzini@redhat.com>, Joel Fernandes <joelaf@google.com>, joel@joelfernandes.org
>
>
> Fifth iteration of the Core-Scheduling feature.
>
> Core scheduling is a feature that only allows trusted tasks to run
> concurrently on cpus sharing compute resources(eg: hyperthreads on a
> core). The goal is to mitigate the core-level side-channel attacks
> without requiring to disable SMT (which has a significant impact on
> performance in some situations). So far, the feature mitigates user-space
> to user-space attacks but not user-space to kernel attack, when one of
> the hardware thread enters the kernel (syscall, interrupt etc).
>
> By default, the feature doesn't change any of the current scheduler
> behavior. The user decides which tasks can run simultaneously on the
> same core (for now by having them in the same tagged cgroup). When
> a tag is enabled in a cgroup and a task from that cgroup is running
> on a hardware thread, the scheduler ensures that only idle or trusted
> tasks run on the other sibling(s). Besides security concerns, this
> feature can also be beneficial for RT and performance applications
> where we want to control how tasks make use of SMT dynamically.
>
> This version was focusing on performance and stability. Couple of
> crashes related to task tagging and cpu hotplug path were fixed.
> This version also improves the performance considerably by making
> task migration and load balancing coresched aware.
>
> In terms of performance, the major difference since the last iteration
> is that now even IO-heavy and mixed-resources workloads are less
> impacted by core-scheduling than by disabling SMT. Both host-level and
> VM-level benchmarks were performed. Details in:
> https://lkml.org/lkml/2020/2/12/1194
> https://lkml.org/lkml/2019/11/1/269
>
> v5 is rebased on top of 5.5.5(449718782a46)
> https://github.com/digitalocean/linux-coresched/tree/coresched/v5-v5.5.y
>