Messages in this thread | | | Date | Fri, 30 Jun 2023 15:41:24 +0200 | Subject | Re: [PATCH v3 0/9] Introduce SMT level and add PowerPC support | From | Laurent Dufour <> |
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Le 30/06/2023 à 15:32, Sachin Sant a écrit : > > >> On 29-Jun-2023, at 8:01 PM, Laurent Dufour <ldufour@linux.ibm.com> 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. >> >> v3: >> Fix a build error in the patch 6/9 > > Successfully tested the V3 version on a Power10 LPAR. Add/remove of > processor core worked correctly, preserving the SMT level (on a kernel > booted with smt-enabled= parameter) > > Laurent (Thanks!) also provided a patch to update the ppc64_cpu & > lparstat utility. With patched ppc64_cpu utility verified that SMT level > changed at runtime was preserved across processor core add (on > a kernel booted without smt-enabled= parameter) > > Based on these test results > > Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Thanks a lot, Sachin!
Once this series is accepted, I'll send the series to update ppc64_cpu.
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