Anton reported that his 4096 cpu (1024 cores in a socket) was taking too long to boot. He also analyzed that most of the time was being spent on updating cpu_core_mask.
Here are some optimizations and fixes to make ppc64_cpu --smt=8/ppc64_cpu --smt=1 run faster and hence boot the kernel also faster. Its based on top of my v4 coregroup support patchset. http://lore.kernel.org/lkml/20200727053230.19753-1-sri...@linux.vnet.ibm.com/t/#u The first two patches should solve Anton's immediate problem. On the unofficial patches, Anton reported that the boot time came from 30 mins to 6 seconds. (Basically a high core count in a single socket configuration). Satheesh also reported similar numbers. The rest are simple cleanups/optimizations. Since cpu_core_mask is an exported symbol for a long duration, lets retain as a snapshot of cpumask_of_node. Architecture: ppc64le Byte Order: Little Endian CPU(s): 160 On-line CPU(s) list: 0-159 Thread(s) per core: 4 Core(s) per socket: 20 Socket(s): 2 NUMA node(s): 2 Model: 2.2 (pvr 004e 1202) Model name: POWER9, altivec supported CPU max MHz: 3800.0000 CPU min MHz: 2166.0000 L1d cache: 32K L1i cache: 32K L2 cache: 512K L3 cache: 10240K NUMA node0 CPU(s): 0-79 NUMA node8 CPU(s): 80-159 without patch (powerpc/next) [ 0.099347] smp: Bringing up secondary CPUs ... [ 0.832513] smp: Brought up 2 nodes, 160 CPUs with powerpc/next + coregroup support patchset [ 0.099241] smp: Bringing up secondary CPUs ... [ 0.835627] smp: Brought up 2 nodes, 160 CPUs with powerpc/next + coregroup + this patchset [ 0.097232] smp: Bringing up secondary CPUs ... [ 0.528457] smp: Brought up 2 nodes, 160 CPUs x ppc64_cpu --smt=1 + ppc64_cpu --smt=4 without patch N Min Max Median Avg Stddev x 100 11.82 17.06 14.01 14.05 1.2665247 + 100 12.25 16.59 13.86 14.1143 1.164293 with patch N Min Max Median Avg Stddev x 100 12.68 16.15 14.24 14.238 0.75489246 + 100 12.93 15.85 14.35 14.2897 0.60041813 Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org> Cc: LKML <linux-ker...@vger.kernel.org> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: Nicholas Piggin <npig...@gmail.com> Cc: Anton Blanchard <an...@ozlabs.org> Cc: Oliver O'Halloran <ooh...@gmail.com> Cc: Nathan Lynch <nath...@linux.ibm.com> Cc: Michael Neuling <mi...@neuling.org> Cc: Gautham R Shenoy <e...@linux.vnet.ibm.com> Cc: Satheesh Rajendran <sathn...@linux.vnet.ibm.com> Cc: Ingo Molnar <mi...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Valentin Schneider <valentin.schnei...@arm.com> Srikar Dronamraju (7): powerpc/topology: Update topology_core_cpumask powerpc/smp: Stop updating cpu_core_mask powerpc/smp: Remove get_physical_package_id powerpc/smp: Optimize remove_cpu_from_masks powerpc/smp: Limit cpus traversed to within a node. powerpc/smp: Stop passing mask to update_mask_by_l2 powerpc/smp: Depend on cpu_l1_cache_map when adding cpus arch/powerpc/include/asm/smp.h | 5 -- arch/powerpc/include/asm/topology.h | 7 +-- arch/powerpc/kernel/smp.c | 79 +++++++++-------------------- 3 files changed, 24 insertions(+), 67 deletions(-) -- 2.17.1
