From: Laurent Dufour <ldufour@linux.ibm.com>
To: "Zhang, Rui" <rui.zhang@intel.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Cc: "npiggin@gmail.com" <npiggin@gmail.com>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"bp@alien8.de" <bp@alien8.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"christophe.leroy@csgroup.eu" <christophe.leroy@csgroup.eu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mpe@ellerman.id.au" <mpe@ellerman.id.au>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: [PATCH v4 00/10] Introduce SMT level and add PowerPC support
Date: Mon, 10 Jul 2023 11:08:03 +0200 [thread overview]
Message-ID: <ff068ea8-c731-3763-066b-2503ffddd0e8@linux.ibm.com> (raw)
In-Reply-To: <c66e3e800a7d257ef7a90749fe567f056f4c3ace.camel@intel.com>
Le 09/07/2023 à 17:25, Zhang, Rui a écrit :
> Hi, Laurent,
>
> I ran into a boot hang regression with latest upstream code, and it
> took me a while to bisect the offending commit and workaround it.
>
> Now I have tested this patch series on an Intel RaptorLake Hybrid
> platform (4 Pcores with HT and 4 Ecores without HT), and it works as
> expected.
>
> So, for patch 1~7 in this series,
>
> Tested-by: Zhang Rui <rui.zhang@intel.com>
Thanks Rui!
> thanks,
> rui
>
> On Wed, 2023-07-05 at 16:51 +0200, Laurent Dufour wrote:
>> I'm taking over the series Michael sent previously [1] which is
>> smartly
>> reviewing the initial series I sent [2]. This series is addressing
>> the
>> comments sent by Thomas and me on the Michael's one.
>>
>> Here is a short introduction to the issue this series is addressing:
>>
>> When a new CPU is added, the kernel is activating all its threads.
>> This
>> leads to weird, but functional, result when adding CPU on a SMT 4
>> system
>> for instance.
>>
>> Here the newly added CPU 1 has 8 threads while the other one has 4
>> threads
>> active (system has been booted with the 'smt-enabled=4' kernel
>> option):
>>
>> ltcden3-lp12:~ # ppc64_cpu --info
>> Core 0: 0* 1* 2* 3* 4 5 6 7
>> Core 1: 8* 9* 10* 11* 12* 13* 14* 15*
>>
>> This mixed SMT level may confused end users and/or some applications.
>>
>> There is no SMT level recorded in the kernel (common code), neither
>> in user
>> space, as far as I know. Such a level is helpful when adding new CPU
>> or
>> when optimizing the energy efficiency (when reactivating CPUs).
>>
>> When SMP and HOTPLUG_SMT are defined, this series is adding a new SMT
>> level
>> (cpu_smt_num_threads) and few callbacks allowing the architecture
>> code to
>> fine control this value, setting a max and a "at boot" level, and
>> controling whether a thread should be onlined or not.
>>
>> v4:
>> Rebase on top of 6.5's updates
>> Remove a dependancy against the X86's symbol
>> cpu_primary_thread_mask
>> v3:
>> Fix a build error in the patch 6/9
>> v2:
>> As Thomas suggested,
>> Reword some commit's description
>> Remove topology_smt_supported()
>> Remove topology_smt_threads_supported()
>> Introduce CONFIG_SMT_NUM_THREADS_DYNAMIC
>> Remove switch() in __store_smt_control()
>> Update kernel-parameters.txt
>>
>> [1]
>> https://lore.kernel.org/linuxppc-dev/20230524155630.794584-1-mpe@ellerman.id.au/
>> [2]
>> https://lore.kernel.org/linuxppc-dev/20230331153905.31698-1-ldufour@linux.ibm.com/
>>
>>
>> Laurent Dufour (2):
>> cpu/hotplug: remove dependancy against cpu_primary_thread_mask
>> cpu/SMT: Remove topology_smt_supported()
>>
>> Michael Ellerman (8):
>> cpu/SMT: Move SMT prototypes into cpu_smt.h
>> cpu/SMT: Move smt/control simple exit cases earlier
>> cpu/SMT: Store the current/max number of threads
>> cpu/SMT: Create topology_smt_thread_allowed()
>> cpu/SMT: Allow enabling partial SMT states via sysfs
>> powerpc/pseries: Initialise CPU hotplug callbacks earlier
>> powerpc: Add HOTPLUG_SMT support
>> powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs
>>
>> .../ABI/testing/sysfs-devices-system-cpu | 1 +
>> .../admin-guide/kernel-parameters.txt | 4 +-
>> arch/Kconfig | 3 +
>> arch/powerpc/Kconfig | 2 +
>> arch/powerpc/include/asm/topology.h | 15 ++
>> arch/powerpc/kernel/smp.c | 8 +-
>> arch/powerpc/platforms/pseries/hotplug-cpu.c | 30 ++--
>> arch/powerpc/platforms/pseries/pseries.h | 2 +
>> arch/powerpc/platforms/pseries/setup.c | 2 +
>> arch/x86/include/asm/topology.h | 4 +-
>> arch/x86/kernel/cpu/common.c | 2 +-
>> arch/x86/kernel/smpboot.c | 8 -
>> include/linux/cpu.h | 25 +--
>> include/linux/cpu_smt.h | 33 ++++
>> kernel/cpu.c | 142 +++++++++++++---
>> --
>> 15 files changed, 196 insertions(+), 85 deletions(-)
>> create mode 100644 include/linux/cpu_smt.h
>>
>
next prev parent reply other threads:[~2023-07-10 9:08 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-05 14:51 [PATCH v4 00/10] Introduce SMT level and add PowerPC support Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 01/10] cpu/hotplug: remove dependancy against cpu_primary_thread_mask Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 02/10] cpu/SMT: Move SMT prototypes into cpu_smt.h Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 03/10] cpu/SMT: Move smt/control simple exit cases earlier Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 04/10] cpu/SMT: Store the current/max number of threads Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 05/10] cpu/SMT: Remove topology_smt_supported() Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 06/10] cpu/SMT: Create topology_smt_thread_allowed() Laurent Dufour
2023-07-05 14:51 ` [PATCH v4 07/10] cpu/SMT: Allow enabling partial SMT states via sysfs Laurent Dufour
2024-04-08 14:13 ` Michal Suchánek
2023-07-05 14:51 ` [PATCH v4 08/10] powerpc/pseries: Initialise CPU hotplug callbacks earlier Laurent Dufour
2023-08-14 10:51 ` Srikar Dronamraju
2023-07-05 14:51 ` [PATCH v4 09/10] powerpc: Add HOTPLUG_SMT support Laurent Dufour
2023-08-14 10:52 ` Srikar Dronamraju
2023-07-05 14:51 ` [PATCH v4 10/10] powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs Laurent Dufour
2023-08-14 10:53 ` Srikar Dronamraju
2023-07-09 15:25 ` [PATCH v4 00/10] Introduce SMT level and add PowerPC support Zhang, Rui
2023-07-10 9:08 ` Laurent Dufour [this message]
2023-07-28 7:40 ` Thomas Gleixner
2023-07-28 14:23 ` Zhang, Rui
2023-07-28 14:51 ` Thomas Gleixner
2023-07-28 7:58 ` Thomas Gleixner
2023-07-31 11:55 ` Laurent Dufour
2023-08-10 6:23 ` Michael Ellerman
2023-08-10 8:51 ` Laurent Dufour
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