[PATCH v4 0/4] x86/smpboot: tidy sched-topology and drop useless SMT level

[PATCH v4 0/4] x86/smpboot: tidy sched-topology and drop useless SMT level

[Li Chen]

From: Li Chen <chenl311@chinatelecom.cn>

This series cleans up sched-domain topology handling and
eliminates hundreds of pointless attach/destroy cycles for large
machines when SMT is not available.

Patch 1, 2, and 3 do some cleanup and refactor.

Patch 4 is a follow-up that simply skip SMT domain when
cpu_smt_num_threads <= 1, so the SMT level never gets created.

Tested on Qemu.

changelog:
v2: fix wording issue as suggested by Thomas [1]
v3: remove pointless memset and adjust PKG index accordingly, as
    suggested by Thomas [2], and refine some other wording issues.
v4: v4: Split refactor patche into three parts (as suggested by Peter [3])
    and refined patch 4 logic (as done by K. [4]).

[1]: https://lore.kernel.org/all/87msa2r018.ffs@tglx/
[2]: https://lore.kernel.org/all/875xglntx1.ffs@tglx/
[3]: https://lkml.org/lkml/2025/6/25/584
[4]: https://lore.kernel.org/lkml/1b706790-2fec-4582-a425-55eeff36c32e@amd.com/

Li Chen (4):
  smpboot: introduce SDTL() helper to tidy sched topology setup
  x86/smpboot: remove redundant CONFIG_SCHED_SMT
  x86/smpboot: moves x86_topology to static initialize and truncate
  x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled

 arch/powerpc/kernel/smp.c      | 34 ++++++++-------------
 arch/s390/kernel/topology.c    | 10 +++----
 arch/x86/kernel/smpboot.c      | 55 ++++++++++++++++------------------
 include/linux/sched/topology.h |  6 ++--
 kernel/sched/topology.c        | 16 ++++------
 5 files changed, 53 insertions(+), 68 deletions(-)

-- 
2.49.0

[PATCH v4 1/4] smpboot: introduce SDTL() helper to tidy sched topology setup

[Li Chen]

From: Li Chen <chenl311@chinatelecom.cn>

Define a small SDTL(maskfn, flagsfn, name) macro and use it to build the
sched_domain_topology_level. Purely a cleanup; behaviour is unchanged.

Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/powerpc/kernel/smp.c      | 34 +++++++++++++---------------------
 arch/s390/kernel/topology.c    | 10 +++++-----
 arch/x86/kernel/smpboot.c      | 21 ++++++---------------
 include/linux/sched/topology.h |  6 +++---
 kernel/sched/topology.c        | 16 ++++++----------
 5 files changed, 33 insertions(+), 54 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 5ac7084eebc0b..b05995e272134 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1700,28 +1700,20 @@ static void __init build_sched_topology(void)
 #ifdef CONFIG_SCHED_SMT
 	if (has_big_cores) {
 		pr_info("Big cores detected but using small core scheduling\n");
-		powerpc_topology[i++] = (struct sched_domain_topology_level){
-			smallcore_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT)
-		};
-	} else {
-		powerpc_topology[i++] = (struct sched_domain_topology_level){
-			cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT)
-		};
-	}
+		powerpc_topology[i++] =
+			SDTL(smallcore_smt_mask, powerpc_smt_flags, SMT);
+	} else
+		powerpc_topology[i++] = SDTL(cpu_smt_mask, powerpc_smt_flags, SMT);
 #endif
-	if (shared_caches) {
-		powerpc_topology[i++] = (struct sched_domain_topology_level){
-			shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE)
-		};
-	}
-	if (has_coregroup_support()) {
-		powerpc_topology[i++] = (struct sched_domain_topology_level){
-			cpu_mc_mask, powerpc_shared_proc_flags, SD_INIT_NAME(MC)
-		};
-	}
-	powerpc_topology[i++] = (struct sched_domain_topology_level){
-		cpu_cpu_mask, powerpc_shared_proc_flags, SD_INIT_NAME(PKG)
-	};
+	if (shared_caches)
+		powerpc_topology[i++] =
+			SDTL(shared_cache_mask, powerpc_shared_cache_flags, CACHE);
+
+	if (has_coregroup_support())
+		powerpc_topology[i++] =
+			SDTL(cpu_mc_mask, powerpc_shared_proc_flags, MC);
+
+	powerpc_topology[i++] = SDTL(cpu_cpu_mask, powerpc_shared_proc_flags, PKG);
 
 	/* There must be one trailing NULL entry left.  */
 	BUG_ON(i >= ARRAY_SIZE(powerpc_topology) - 1);
diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 3df048e190b11..ccf5dcc56f86d 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -531,11 +531,11 @@ static const struct cpumask *cpu_drawer_mask(int cpu)
 }
 
 static struct sched_domain_topology_level s390_topology[] = {
-	{ cpu_thread_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
-	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
-	{ cpu_book_mask, SD_INIT_NAME(BOOK) },
-	{ cpu_drawer_mask, SD_INIT_NAME(DRAWER) },
-	{ cpu_cpu_mask, SD_INIT_NAME(PKG) },
+	SDTL(cpu_thread_mask, cpu_smt_flags, SMT),
+	SDTL(cpu_coregroup_mask, cpu_core_flags, MC),
+	SDTL(cpu_book_mask, NULL, BOOK),
+	SDTL(cpu_drawer_mask, NULL, DRAWER),
+	SDTL(cpu_cpu_mask, NULL, PKG),
 	{ NULL, },
 };
 
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 58ede3fa6a75b..55f09946c791b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -485,35 +485,26 @@ static void __init build_sched_topology(void)
 	int i = 0;
 
 #ifdef CONFIG_SCHED_SMT
-	x86_topology[i++] = (struct sched_domain_topology_level){
-		cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT)
-	};
+	x86_topology[i++] = SDTL(cpu_smt_mask, cpu_smt_flags, SMT);
 #endif
 #ifdef CONFIG_SCHED_CLUSTER
-	x86_topology[i++] = (struct sched_domain_topology_level){
-		cpu_clustergroup_mask, x86_cluster_flags, SD_INIT_NAME(CLS)
-	};
+	x86_topology[i++] = SDTL(cpu_clustergroup_mask, x86_cluster_flags, CLS);
 #endif
 #ifdef CONFIG_SCHED_MC
-	x86_topology[i++] = (struct sched_domain_topology_level){
-		cpu_coregroup_mask, x86_core_flags, SD_INIT_NAME(MC)
-	};
+	x86_topology[i++] = SDTL(cpu_coregroup_mask, x86_core_flags, MC);
 #endif
 	/*
 	 * When there is NUMA topology inside the package skip the PKG domain
 	 * since the NUMA domains will auto-magically create the right spanning
 	 * domains based on the SLIT.
 	 */
-	if (!x86_has_numa_in_package) {
-		x86_topology[i++] = (struct sched_domain_topology_level){
-			cpu_cpu_mask, x86_sched_itmt_flags, SD_INIT_NAME(PKG)
-		};
-	}
+	if (!x86_has_numa_in_package)
+		x86_topology[i++] = SDTL(cpu_cpu_mask, x86_sched_itmt_flags, PKG);
 
 	/*
 	 * There must be one trailing NULL entry left.
 	 */
-	BUG_ON(i >= ARRAY_SIZE(x86_topology)-1);
+	BUG_ON(i >= ARRAY_SIZE(x86_topology) - 1);
 
 	set_sched_topology(x86_topology);
 }
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 198bb5cc1774b..0b53e372c445c 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -197,9 +197,9 @@ struct sched_domain_topology_level {
 extern void __init set_sched_topology(struct sched_domain_topology_level *tl);
 extern void sched_update_asym_prefer_cpu(int cpu, int old_prio, int new_prio);
 
-
-# define SD_INIT_NAME(type)		.name = #type
-
+#define SDTL(maskfn, flagsfn, dname) \
+	((struct sched_domain_topology_level) \
+	    { .mask = maskfn, .sd_flags = flagsfn, .name = #dname, .numa_level = 0 })
 #else /* CONFIG_SMP */
 
 struct sched_domain_attr;
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index b958fe48e0205..e6ec65ae4b75d 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1739,17 +1739,17 @@ sd_init(struct sched_domain_topology_level *tl,
  */
 static struct sched_domain_topology_level default_topology[] = {
 #ifdef CONFIG_SCHED_SMT
-	{ cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
+	SDTL(cpu_smt_mask, cpu_smt_flags, SMT),
 #endif
 
 #ifdef CONFIG_SCHED_CLUSTER
-	{ cpu_clustergroup_mask, cpu_cluster_flags, SD_INIT_NAME(CLS) },
+	SDTL(cpu_clustergroup_mask, cpu_cluster_flags, CLS),
 #endif
 
 #ifdef CONFIG_SCHED_MC
-	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
+	SDTL(cpu_coregroup_mask, cpu_core_flags, MC),
 #endif
-	{ cpu_cpu_mask, SD_INIT_NAME(PKG) },
+	SDTL(cpu_cpu_mask, NULL, PKG),
 	{ NULL, },
 };
 
@@ -2010,11 +2010,7 @@ void sched_init_numa(int offline_node)
 	/*
 	 * Add the NUMA identity distance, aka single NODE.
 	 */
-	tl[i++] = (struct sched_domain_topology_level){
-		.mask = sd_numa_mask,
-		.numa_level = 0,
-		SD_INIT_NAME(NODE)
-	};
+	tl[i++] = SDTL(sd_numa_mask, NULL, NODE);
 
 	/*
 	 * .. and append 'j' levels of NUMA goodness.
@@ -2025,7 +2021,7 @@ void sched_init_numa(int offline_node)
 			.sd_flags = cpu_numa_flags,
 			.flags = SDTL_OVERLAP,
 			.numa_level = j,
-			SD_INIT_NAME(NUMA)
+			.name = "NUMA",
 		};
 	}
 
-- 
2.49.0

Re: [PATCH v4 1/4] smpboot: introduce SDTL() helper to tidy sched topology setup

[K Prateek Nayak]

Hello Li,

Apart from few comments inline below, feel free to include:

Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>

for the entire series.

On 7/6/2025 8:36 AM, Li Chen wrote:
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 198bb5cc1774b..0b53e372c445c 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -197,9 +197,9 @@ struct sched_domain_topology_level {
>  extern void __init set_sched_topology(struct sched_domain_topology_level *tl);
>  extern void sched_update_asym_prefer_cpu(int cpu, int old_prio, int new_prio);
>  
> -
> -# define SD_INIT_NAME(type)		.name = #type
> -
> +#define SDTL(maskfn, flagsfn, dname) \
> +	((struct sched_domain_topology_level) \
> +	    { .mask = maskfn, .sd_flags = flagsfn, .name = #dname, .numa_level = 0 })

I prefer the following alignment:

#define SDTL(maskfn, flagsfn, dname) ((struct sched_domain_topology_level) \
	{ .mask = maskfn, .sd_flags = flagsfn, .name = #dname })

instead of having 3 lines. "numa_level" is 0 by default so I don't think
we need to explicitly specify it again.

Also perhaps the macro can be named "SDTL_INIT()" to keep consistent
with the naming convention.

>  #else /* CONFIG_SMP */

A bunch of the CONFIG_SMP related ifdeffry is being removed for the
next cycle. You can perhaps rebase the series on top of the tip tree
(git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git)

>  
>  struct sched_domain_attr;

[..snip..]

> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index b958fe48e0205..e6ec65ae4b75d 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -2025,7 +2021,7 @@ void sched_init_numa(int offline_node)
>  			.sd_flags = cpu_numa_flags,
>  			.flags = SDTL_OVERLAP,
>  			.numa_level = j,
> -			SD_INIT_NAME(NUMA)
> +			.name = "NUMA",

This can use SDTL() macro too. Just explicitly set "tl[i].numa_level" to
"j" after.

>  		};
>  	}
>  

-- 
Thanks and Regards,
Prateek

Re: [PATCH v4 1/4] smpboot: introduce SDTL() helper to tidy sched topology setup

[Li Chen]

Hi K,

Thanks for your reviews and test! I have addressed all issues in v5:
https://www.spinics.net/lists/kernel/msg5761848.html

 ---- On Mon, 07 Jul 2025 13:33:53 +0800  K Prateek Nayak <kprateek.nayak@amd.com> wrote --- 
 > Hello Li,
 > 
 > Apart from few comments inline below, feel free to include:
 > 
 > Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
 > 
 > for the entire series.
 > 
 > On 7/6/2025 8:36 AM, Li Chen wrote:
 > > diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
 > > index 198bb5cc1774b..0b53e372c445c 100644
 > > --- a/include/linux/sched/topology.h
 > > +++ b/include/linux/sched/topology.h
 > > @@ -197,9 +197,9 @@ struct sched_domain_topology_level {
 > >  extern void __init set_sched_topology(struct sched_domain_topology_level *tl);
 > >  extern void sched_update_asym_prefer_cpu(int cpu, int old_prio, int new_prio);
 > >  
 > > -
 > > -# define SD_INIT_NAME(type)        .name = #type
 > > -
 > > +#define SDTL(maskfn, flagsfn, dname) \
 > > +    ((struct sched_domain_topology_level) \
 > > +        { .mask = maskfn, .sd_flags = flagsfn, .name = #dname, .numa_level = 0 })
 > 
 > I prefer the following alignment:
 > 
 > #define SDTL(maskfn, flagsfn, dname) ((struct sched_domain_topology_level) \
 >     { .mask = maskfn, .sd_flags = flagsfn, .name = #dname })
 > 
 > instead of having 3 lines. "numa_level" is 0 by default so I don't think
 > we need to explicitly specify it again.
 > 
 > Also perhaps the macro can be named "SDTL_INIT()" to keep consistent
 > with the naming convention.
 > 
 > >  #else /* CONFIG_SMP */
 > 
 > A bunch of the CONFIG_SMP related ifdeffry is being removed for the
 > next cycle. You can perhaps rebase the series on top of the tip tree
 > (git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git)
 > 
 > >  
 > >  struct sched_domain_attr;
 > 
 > [..snip..]
 > 
 > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
 > > index b958fe48e0205..e6ec65ae4b75d 100644
 > > --- a/kernel/sched/topology.c
 > > +++ b/kernel/sched/topology.c
 > > @@ -2025,7 +2021,7 @@ void sched_init_numa(int offline_node)
 > >              .sd_flags = cpu_numa_flags,
 > >              .flags = SDTL_OVERLAP,
 > >              .numa_level = j,
 > > -            SD_INIT_NAME(NUMA)
 > > +            .name = "NUMA",
 > 
 > This can use SDTL() macro too. Just explicitly set "tl[i].numa_level" to
 > "j" after.
 > 
 > >          };
 > >      }
 > >  
 > 
 > -- 
 > Thanks and Regards,
 > Prateek
 > 
 > 
Regards,

Li​

[PATCH v4 2/4] x86/smpboot: remove redundant CONFIG_SCHED_SMT

[Li Chen]

From: Li Chen <chenl311@chinatelecom.cn>

CONFIG_SCHED_SMT is default y if SMP is enabled,
so let's simply drop CONFIG_SCHED_SMT.

Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/smpboot.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 55f09946c791b..6e36306632792 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -484,9 +484,7 @@ static void __init build_sched_topology(void)
 {
 	int i = 0;
 
-#ifdef CONFIG_SCHED_SMT
 	x86_topology[i++] = SDTL(cpu_smt_mask, cpu_smt_flags, SMT);
-#endif
 #ifdef CONFIG_SCHED_CLUSTER
 	x86_topology[i++] = SDTL(cpu_clustergroup_mask, x86_cluster_flags, CLS);
 #endif
-- 
2.49.0

[PATCH v4 3/4] x86/smpboot: moves x86_topology to static initialize and truncate

[Li Chen]

From: Li Chen <chenl311@chinatelecom.cn>

The #ifdeffery and the initializers in build_sched_topology() are just
disgusting.

Statically initialize the domain levels in the topology array and let
build_sched_topology() invalidate the package domain level when NUMA in
package is available.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
---
 arch/x86/kernel/smpboot.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 6e36306632792..cd70e5322462a 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -478,32 +478,30 @@ static int x86_cluster_flags(void)
  */
 static bool x86_has_numa_in_package;
 
-static struct sched_domain_topology_level x86_topology[6];
-
-static void __init build_sched_topology(void)
-{
-	int i = 0;
-
-	x86_topology[i++] = SDTL(cpu_smt_mask, cpu_smt_flags, SMT);
+static struct sched_domain_topology_level x86_topology[] = {
+	SDTL(cpu_smt_mask, cpu_smt_flags, SMT),
 #ifdef CONFIG_SCHED_CLUSTER
-	x86_topology[i++] = SDTL(cpu_clustergroup_mask, x86_cluster_flags, CLS);
+	SDTL(cpu_clustergroup_mask, x86_cluster_flags, CLS),
 #endif
 #ifdef CONFIG_SCHED_MC
-	x86_topology[i++] = SDTL(cpu_coregroup_mask, x86_core_flags, MC);
+	SDTL(cpu_coregroup_mask, x86_core_flags, MC),
 #endif
-	/*
-	 * When there is NUMA topology inside the package skip the PKG domain
-	 * since the NUMA domains will auto-magically create the right spanning
-	 * domains based on the SLIT.
-	 */
-	if (!x86_has_numa_in_package)
-		x86_topology[i++] = SDTL(cpu_cpu_mask, x86_sched_itmt_flags, PKG);
+	SDTL(cpu_cpu_mask, x86_sched_itmt_flags, PKG),
+	{ NULL },
+};
 
+static void __init build_sched_topology(void)
+{
 	/*
-	 * There must be one trailing NULL entry left.
+	 * When there is NUMA topology inside the package invalidate the
+	 * PKG domain since the NUMA domains will auto-magically create the
+	 * right spanning domains based on the SLIT.
 	 */
-	BUG_ON(i >= ARRAY_SIZE(x86_topology) - 1);
+	if (x86_has_numa_in_package) {
+		unsigned int pkgdom = ARRAY_SIZE(x86_topology) - 2;
 
+		memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom]));
+	}
 	set_sched_topology(x86_topology);
 }
 
-- 
2.49.0

[PATCH v4 4/4] x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled

[Li Chen]

From: Li Chen <chenl311@chinatelecom.cn>

Currently, the SMT domain is added into sched_domain_topology by default.

If cpu_attach_domain() finds that the CPU SMT domain’s cpumask_weight
is just 1, it will destroy it.

On a large machine, such as one with 512 cores, this results in
512 redundant domain attach/destroy operations.

Avoid these unnecessary operations by simply checking
cpu_smt_num_threads and skip SMT domain if the SMT domain is not
enabled.

Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
---
 arch/x86/kernel/smpboot.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index cd70e5322462a..8c1960a455bfb 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -492,6 +492,8 @@ static struct sched_domain_topology_level x86_topology[] = {
 
 static void __init build_sched_topology(void)
 {
+	struct sched_domain_topology_level *topology = x86_topology;
+
 	/*
 	 * When there is NUMA topology inside the package invalidate the
 	 * PKG domain since the NUMA domains will auto-magically create the
@@ -502,7 +504,15 @@ static void __init build_sched_topology(void)
 
 		memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom]));
 	}
-	set_sched_topology(x86_topology);
+
+    /*
+     * Drop the SMT domains if there is only one thread per-core
+     * since it'll get degenerated by the scheduler anyways.
+     */
+	if (cpu_smt_num_threads <= 1)
+		++topology;
+
+	set_sched_topology(topology);
 }
 
 void set_cpu_sibling_map(int cpu)
-- 
2.49.0

Re: [PATCH v4 4/4] x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled

[K Prateek Nayak]

Hello Li,

On 7/6/2025 8:36 AM, Li Chen wrote:
> From: Li Chen <chenl311@chinatelecom.cn>
> 
> Currently, the SMT domain is added into sched_domain_topology by default.
> 
> If cpu_attach_domain() finds that the CPU SMT domain’s cpumask_weight
> is just 1, it will destroy it.
> 
> On a large machine, such as one with 512 cores, this results in
> 512 redundant domain attach/destroy operations.
> 
> Avoid these unnecessary operations by simply checking
> cpu_smt_num_threads and skip SMT domain if the SMT domain is not
> enabled.
> 
> Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>

"Suggested-by:" should be fine :)

> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
> Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
> ---
>  arch/x86/kernel/smpboot.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index cd70e5322462a..8c1960a455bfb 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -492,6 +492,8 @@ static struct sched_domain_topology_level x86_topology[] = {
>  
>  static void __init build_sched_topology(void)
>  {
> +	struct sched_domain_topology_level *topology = x86_topology;
> +
>  	/*
>  	 * When there is NUMA topology inside the package invalidate the
>  	 * PKG domain since the NUMA domains will auto-magically create the
> @@ -502,7 +504,15 @@ static void __init build_sched_topology(void)
>  
>  		memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom]));
>  	}
> -	set_sched_topology(x86_topology);
> +
> +    /*
> +     * Drop the SMT domains if there is only one thread per-core
> +     * since it'll get degenerated by the scheduler anyways.
> +     */

The comment above has spaces instead of tab before it.

> +	if (cpu_smt_num_threads <= 1)
> +		++topology;> +
> +	set_sched_topology(topology);
>  }
>  
>  void set_cpu_sibling_map(int cpu)

-- 
Thanks and Regards,
Prateek