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cpu/SMT: Create topology_smt_thread_allowed() 

JIRA: https://issues.redhat.com/browse/RHEL-5838

commit 38253464bc821d6de6bba81bb1412ebb36f6cbd1
Author: Michael Ellerman <mpe@ellerman.id.au>
Date:   Wed Jul 5 16:51:39 2023 +0200

    cpu/SMT: Create topology_smt_thread_allowed()

    Some architectures allows partial SMT states, i.e. when not all SMT threads
    are brought online.

    To support that, add an architecture helper which checks whether a given
    CPU is allowed to be brought online depending on how many SMT threads are
    currently enabled. Since this is only applicable to architecture supporting
    partial SMT, only these architectures should select the new configuration
    variable CONFIG_SMT_NUM_THREADS_DYNAMIC. For the other architectures, not
    supporting the partial SMT states, there is no need to define
    topology_cpu_smt_allowed(), the generic code assumed that all the threads
    are allowed or only the primary ones.

    Call the helper from cpu_smt_enable(), and cpu_smt_allowed() when SMT is
    enabled, to check if the particular thread should be onlined. Notably,
    also call it from cpu_smt_disable() if CPU_SMT_ENABLED, to allow
    offlining some threads to move from a higher to lower number of threads
    online.

    [ ldufour: Slightly reword the commit's description ]
    [ ldufour: Introduce CONFIG_SMT_NUM_THREADS_DYNAMIC ]

    Suggested-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Zhang Rui <rui.zhang@intel.com>
    Link: https://lore.kernel.org/r/20230705145143.40545-7-ldufour@linux.ibm.com

Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>
This commit is contained in:
Mamatha Inamdar 2023-11-07 09:19:32 +00:00
parent 2efae49800
commit f2f0751cbe
2 changed files with 26 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/Kconfig
View File

@ -34,6 +34,9 @@ config ARCH_HAS_SUBPAGE_FAULTS
config HOTPLUG_SMT
bool
config SMT_NUM_THREADS_DYNAMIC
bool
config GENERIC_ENTRY
bool

24
kernel/cpu.c
View File

@ -457,9 +457,23 @@ static int __init smt_cmdline_disable(char *str)
}
early_param("nosmt", smt_cmdline_disable);
/*
* For Archicture supporting partial SMT states check if the thread is allowed.
* Otherwise this has already been checked through cpu_smt_max_threads when
* setting the SMT level.
*/
static inline bool cpu_smt_thread_allowed(unsigned int cpu)
{
#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
return topology_smt_thread_allowed(cpu);
#else
return true;
#endif
}
static inline bool cpu_smt_allowed(unsigned int cpu)
{
if (cpu_smt_control == CPU_SMT_ENABLED)
if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
return true;
if (topology_is_primary_thread(cpu))
@ -2231,6 +2245,12 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
for_each_online_cpu(cpu) {
if (topology_is_primary_thread(cpu))
continue;
/*
* Disable can be called with CPU_SMT_ENABLED when changing
* from a higher to lower number of SMT threads per core.
*/
if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
continue;
ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
if (ret)
break;
@ -2265,6 +2285,8 @@ int cpuhp_smt_enable(void)
/* Skip online CPUs and CPUs on offline nodes */
if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
continue;
if (!cpu_smt_thread_allowed(cpu))
continue;
ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
if (ret)
break;