Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
LoongArch: Add HOTPLUG_SMT implementation
For benchmarking or debugging purpose, we usually want to control SMT
via boot parameter and sysfs knobs. So add HOTPLUG_SMT implementation.
1. Boot parameters:
nosmt: Disable SMT, can be enabled via sysfs knobs.
nosmt=force: Disable SMT, cannot be enabled via sysfs knobs.
2. Runtime sysfs controls:
Write "on", "off", "forceoff" or the number of SMT threads (1, 2, ...)
to /sys/devices/system/cpu/smt/control.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
+15
-1
+1
-1
Documentation/admin-guide/kernel-parameters.txt
+1
-1
Documentation/admin-guide/kernel-parameters.txt
···
4585
4585
nosmt [KNL,MIPS,PPC,EARLY] Disable symmetric multithreading (SMT).
4586
4586
Equivalent to smt=1.
4587
4587
4588
-
[KNL,X86,PPC,S390] Disable symmetric multithreading (SMT).
4588
+
[KNL,LOONGARCH,X86,PPC,S390] Disable symmetric multithreading (SMT).
4589
4589
nosmt=force: Force disable SMT, cannot be undone
4590
4590
via the sysfs control file.
4591
4591
+1
arch/loongarch/Kconfig
+1
arch/loongarch/Kconfig
+13
arch/loongarch/kernel/smp.c
+13
arch/loongarch/kernel/smp.c
···
365
365
void __init loongson_prepare_cpus(unsigned int max_cpus)
366
366
{
367
367
int i = 0;
368
+
int threads_per_core = 0;
368
369
369
370
parse_acpi_topology();
370
371
cpu_data[0].global_id = cpu_logical_map(0);
372
+
373
+
if (!pptt_enabled)
374
+
threads_per_core = 1;
375
+
else {
376
+
for_each_possible_cpu(i) {
377
+
if (cpu_to_node(i) != 0)
378
+
continue;
379
+
if (cpus_are_siblings(0, i))
380
+
threads_per_core++;
381
+
}
382
+
}
371
383
372
384
for (i = 0; i < loongson_sysconf.nr_cpus; i++) {
373
385
set_cpu_present(i, true);
···
387
375
}
388
376
389
377
per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
378
+
cpu_smt_set_num_threads(threads_per_core, threads_per_core);
390
379
}
391
380
392
381
/*