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    SubjectRe: [PATCH] powerpc/smp: Dynamically build powerpc topology
    * Michael Ellerman <mpe@ellerman.id.au> [2023-10-20 23:10:55]:

    > Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
    > > Currently there are four powerpc specific sched topologies. These are
    > > all statically defined. However not all these topologies are used by
    > > all powerpc systems.
    > >
    > > To avoid unnecessary degenerations by the scheduler , masks and flags
    > > are compared. However if the sched topologies are build dynamically then
    > > the code is simpler and there are greater chances of avoiding
    > > degenerations.
    > >
    > > Even x86 builds its sched topologies dynamically and new changes are
    > > very similar to the way x86 is building its topologies.
    > >
    > > System Configuration
    > > type=Shared mode=Uncapped smt=8 lcpu=128 mem=1063126592 kB cpus=96 ent=40.00
    > >
    > > $ lscpu
    > > Architecture: ppc64le
    > > Byte Order: Little Endian
    > > CPU(s): 1024
    > > On-line CPU(s) list: 0-1023
    > > Model name: POWER10 (architected), altivec supported
    > > Model: 2.0 (pvr 0080 0200)
    > > Thread(s) per core: 8
    > > Core(s) per socket: 32
    > > Socket(s): 4
    > > Hypervisor vendor: pHyp
    > > Virtualization type: para
    > > L1d cache: 8 MiB (256 instances)
    > > L1i cache: 12 MiB (256 instances)
    > > NUMA node(s): 4
    > >
    > > From dmesg of v6.5
    > > [ 0.174444] smp: Bringing up secondary CPUs ...
    > > [ 3.918535] smp: Brought up 4 nodes, 1024 CPUs
    > > [ 38.001402] sysrq: Changing Loglevel
    > > [ 38.001446] sysrq: Loglevel set to 9
    > >
    > > From dmesg of v6.5 + patch
    > > [ 0.174462] smp: Bringing up secondary CPUs ...
    > > [ 3.421462] smp: Brought up 4 nodes, 1024 CPUs
    > > [ 35.417917] sysrq: Changing Loglevel
    > > [ 35.417959] sysrq: Loglevel set to 9
    > >
    > > 5 runs of ppc64_cpu --smt=1 (time measured: lesser is better)
    > > Kernel N Min Max Median Avg Stddev %Change
    > > v6.5 5 518.08 574.27 528.61 535.388 22.341542
    > > +patch 5 481.73 495.47 484.21 486.402 5.7997 -9.14963
    > >
    > > 5 runs of ppc64_cpu --smt=8 (time measured: lesser is better)
    > > Kernel N Min Max Median Avg Stddev %Change
    > > v6.5 5 1094.12 1117.1 1108.97 1106.3 8.606361
    > > +patch 5 1067.5 1090.03 1073.89 1076.574 9.4189347 -2.68697
    > >
    > > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    > > ---
    > > arch/powerpc/kernel/smp.c | 78 ++++++++++++++-------------------------
    > > 1 file changed, 28 insertions(+), 50 deletions(-)
    > >
    > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
    > > index 48b8161179a8..c16443a04c26 100644
    > > --- a/arch/powerpc/kernel/smp.c
    > > +++ b/arch/powerpc/kernel/smp.c
    > > @@ -92,15 +92,6 @@ EXPORT_PER_CPU_SYMBOL(cpu_l2_cache_map);
    > > EXPORT_PER_CPU_SYMBOL(cpu_core_map);
    > > EXPORT_SYMBOL_GPL(has_big_cores);
    > >
    > > -enum {
    > > -#ifdef CONFIG_SCHED_SMT
    > > - smt_idx,
    > > -#endif
    > > - cache_idx,
    > > - mc_idx,
    > > - die_idx,
    > > -};
    > > -
    > > #define MAX_THREAD_LIST_SIZE 8
    > > #define THREAD_GROUP_SHARE_L1 1
    > > #define THREAD_GROUP_SHARE_L2_L3 2
    > > @@ -1048,16 +1039,6 @@ static const struct cpumask *cpu_mc_mask(int cpu)
    > > return cpu_coregroup_mask(cpu);
    > > }
    > >
    > > -static struct sched_domain_topology_level powerpc_topology[] = {
    > > -#ifdef CONFIG_SCHED_SMT
    > > - { cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT) },
    > > -#endif
    > > - { shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE) },
    > > - { cpu_mc_mask, powerpc_shared_proc_flags, SD_INIT_NAME(MC) },
    > > - { cpu_cpu_mask, powerpc_shared_proc_flags, SD_INIT_NAME(DIE) },
    > > - { NULL, },
    > > -};
    >
    > This doesn't apply on my next or upstream.
    >
    > It looks like it depends on your other 6-patch series. Please append
    > this patch to that series.
    >
    > cheers

    Ok, will do the needful in the next iteration.

    --
    Thanks and Regards
    Srikar Dronamraju

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