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* [PATCH v4 0/3] Preventing job distribution to isolated CPUs
@ 2020-06-25 22:34 Nitesh Narayan Lal
  2020-06-25 22:34 ` [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs Nitesh Narayan Lal
                   ` (2 more replies)
  0 siblings, 3 replies; 48+ messages in thread
From: Nitesh Narayan Lal @ 2020-06-25 22:34 UTC (permalink / raw)
  To: linux-kernel, linux-api, frederic, mtosatti, juri.lelli, abelits,
	bhelgaas, linux-pci, rostedt, mingo, peterz, tglx, davem, akpm,
	sfr, stephen, rppt, jinyuqi, zhangshaokun

This patch-set is originated from one of the patches that have been
posted earlier as a part of "Task_isolation" mode [1] patch series
by Alex Belits <abelits@marvell.com>. There are only a couple of
changes that I am proposing in this patch-set compared to what Alex
has posted earlier.
 
 
Context
=======
On a broad level, all three patches that are included in this patch
set are meant to improve the driver/library to respect isolated
CPUs by not pinning any job on it. Not doing so could impact
the latency values in RT use-cases.


Patches
=======
* Patch1:
  The first patch is meant to make cpumask_local_spread()
  aware of the isolated CPUs. It ensures that the CPUs that
  are returned by this API only includes housekeeping CPUs.

* Patch2:
  This patch ensures that a probe function that is called
  using work_on_cpu() doesn't run any task on an isolated CPU.

* Patch3:
  This patch makes store_rps_map() aware of the isolated
  CPUs so that rps don't queue any jobs on an isolated CPU. 


Proposed Changes
================
To fix the above-mentioned issues Alex has used housekeeping_cpumask().
The only changes that I am proposing here are:
- Removing the dependency on CONFIG_TASK_ISOLATION that was proposed by
  Alex. As it should be safe to rely on housekeeping_cpumask()
  even when we don't have any isolated CPUs and we want
  to fall back to using all available CPUs in any of the above scenarios.
- Using both HK_FLAG_DOMAIN and HK_FLAG_WQ in Patch2 & 3, this is
  because we would want the above fixes not only when we have isolcpus but
  also with something like systemd's CPU affinity.


Testing
=======
* Patch 1:
  Fix for cpumask_local_spread() is tested by creating VFs, loading
  iavf module and by adding a tracepoint to confirm that only housekeeping
  CPUs are picked when an appropriate profile is set up and all remaining
  CPUs when no CPU isolation is configured.

* Patch 2:
  To test the PCI fix, I hotplugged a virtio-net-pci from qemu console
  and forced its addition to a specific node to trigger the code path that
  includes the proposed fix and verified that only housekeeping CPUs
  are included via tracepoint.

* Patch 3:
  To test the fix in store_rps_map(), I tried configuring an isolated
  CPU by writing to /sys/class/net/en*/queues/rx*/rps_cpus which
  resulted in 'write error: Invalid argument' error. For the case
  where a non-isolated CPU is writing in rps_cpus the above operation
  succeeded without any error.


Changes from v3[2]:
==================
- In patch 1, replaced HK_FLAG_WQ with HK_FLAG_MANAGED_IRQ based on the
  suggestion from Frederic Weisbecker.

Changes from v2[3]:
==================
Both the following suggestions are from Peter Zijlstra.
- Patch1: Removed the extra while loop from cpumask_local_spread and fixed
  the code styling issues.
- Patch3: Change to use cpumask_empty() for verifying that the requested
  CPUs are available in the the housekeeping CPUs.

Changes from v1[4]:
==================
- Included the suggestions made by Bjorn Helgaas in the commit message.
- Included the 'Reviewed-by' and 'Acked-by' received for Patch-2.


[1] https://patchwork.ozlabs.org/project/netdev/patch/51102eebe62336c6a4e584c7a503553b9f90e01c.camel@marvell.com/
[2] https://patchwork.ozlabs.org/project/linux-pci/cover/20200623192331.215557-1-nitesh@redhat.com/
[3] https://patchwork.ozlabs.org/project/linux-pci/cover/20200622234510.240834-1-nitesh@redhat.com/
[4] https://patchwork.ozlabs.org/project/linux-pci/cover/20200610161226.424337-1-nitesh@redhat.com/


Alex Belits (3):
  lib: Restrict cpumask_local_spread to houskeeping CPUs
  PCI: Restrict probe functions to housekeeping CPUs
  net: Restrict receive packets queuing to housekeeping CPUs

 drivers/pci/pci-driver.c |  5 ++++-
 lib/cpumask.c            | 16 +++++++++++-----
 net/core/net-sysfs.c     | 10 +++++++++-
 3 files changed, 24 insertions(+), 7 deletions(-)

-- 


^ permalink raw reply	[flat|nested] 48+ messages in thread

end of thread, other threads:[~2021-05-03 13:16 UTC | newest]

Thread overview: 48+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-25 22:34 [PATCH v4 0/3] Preventing job distribution to isolated CPUs Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs Nitesh Narayan Lal
2020-06-29 16:11   ` Nitesh Narayan Lal
2020-07-01  0:32     ` Andrew Morton
2020-07-01  0:47       ` Nitesh Narayan Lal
2021-01-27 11:57   ` Robin Murphy
2021-01-27 12:19     ` Marcelo Tosatti
2021-01-27 12:36       ` Robin Murphy
2021-01-27 13:09         ` Marcelo Tosatti
2021-01-27 13:49           ` Robin Murphy
2021-01-27 14:16           ` Nitesh Narayan Lal
2021-01-28 15:56           ` Thomas Gleixner
2021-01-28 16:33             ` Marcelo Tosatti
     [not found]             ` <02ac9d85-7ddd-96da-1252-4663feea7c9f@marvell.com>
2021-02-01 17:50               ` [EXT] " Marcelo Tosatti
2021-01-28 16:02       ` Thomas Gleixner
2021-01-28 16:59         ` Marcelo Tosatti
2021-01-28 17:35           ` Nitesh Narayan Lal
2021-01-28 20:01           ` Thomas Gleixner
     [not found]             ` <d2a4dc97-a9ed-e0e7-3b9c-c56ae46f6608@redhat.com>
     [not found]               ` <20210129142356.GB40876@fuller.cnet>
2021-01-29 17:34                 ` [EXT] " Alex Belits
     [not found]                 ` <18584612-868c-0f88-5de2-dc93c8638816@redhat.com>
2021-02-05 19:56                   ` Thomas Gleixner
2021-02-04 18:15             ` Marcelo Tosatti
2021-02-04 18:47               ` Nitesh Narayan Lal
2021-02-04 19:06                 ` Marcelo Tosatti
2021-02-04 19:17                   ` Nitesh Narayan Lal
2021-02-05 22:23                     ` Thomas Gleixner
2021-02-05 22:26                       ` Thomas Gleixner
2021-02-07  0:43                       ` Nitesh Narayan Lal
2021-02-11 15:55                         ` Nitesh Narayan Lal
2021-03-04 18:15                           ` Nitesh Narayan Lal
     [not found]                             ` <faa8d84e-db67-7fbe-891e-f4987f106b20@marvell.com>
2021-03-04 23:23                               ` [EXT] " Nitesh Narayan Lal
2021-04-06 17:22                             ` Jesse Brandeburg
2021-04-07 15:18                               ` Nitesh Narayan Lal
2021-04-08 18:49                                 ` Nitesh Narayan Lal
2021-04-14 16:11                                 ` Jesse Brandeburg
2021-04-15 22:11                                   ` Nitesh Narayan Lal
2021-04-29 21:44                                     ` Nitesh Lal
2021-04-30  1:48                                       ` Jesse Brandeburg
2021-04-30 13:10                                         ` Nitesh Lal
2021-04-30  7:10                                       ` Thomas Gleixner
2021-04-30 16:14                                         ` Nitesh Lal
2021-04-30 18:21                                           ` Thomas Gleixner
2021-04-30 21:07                                             ` Nitesh Lal
2021-05-01  2:21                                               ` Jesse Brandeburg
2021-05-03 13:15                                                 ` Nitesh Lal
2020-06-25 22:34 ` [Patch v4 2/3] PCI: Restrict probe functions to housekeeping CPUs Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 3/3] net: Restrict receive packets queuing " Nitesh Narayan Lal
2020-06-26 11:14   ` Peter Zijlstra
2020-06-26 17:20     ` David Miller

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