linux-kernel - Re: [PATCH] powerpc/smp: Dynamically build powerpc topology

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Message-ID: <20231020132105.GN2194132@linux.vnet.ibm.com>
Date:   Fri, 20 Oct 2023 18:51:05 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Peter Zijlstra <peterz@...radead.org>, ndesaulniers@...gle.com,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/smp: Dynamically build powerpc topology

* Michael Ellerman <mpe@...erman.id.au> [2023-10-20 23:10:55]:

> Srikar Dronamraju <srikar@...ux.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@...ux.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