Thread (30 messages) 30 messages, 5 authors, 2021-10-07

Re: [PATCH RESEND 0/3] Represent cluster topology and enable load balance between clusters

From: Barry Song <hidden>
Date: 2021-10-05 09:06:48
Also in: linux-acpi, lkml

On Tue, Oct 5, 2021 at 9:05 PM Peter Zijlstra [off-list ref] wrote:
On Sat, Oct 02, 2021 at 08:09:58PM +1300, Barry Song wrote:
quoted
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7e4651a1aaf4..86821e83b935 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -993,8 +993,13 @@ config SCHED_CLUSTER
        bool "Cluster scheduler support"
        help
          Cluster scheduler support improves the CPU scheduler's decision
+         making when dealing with machines that have clusters of CPUs.
+         Cluster usually means a couple of CPUs which are placed closely
+         by sharing mid-level caches, last-level cache tags or internal
+         busses. For example, on Hisilicon Kunpeng920, each 4 CPUs share
+         LLC cache tags. This feature isn't a universal win because it
+         can bring a cost of slightly increased overhead in some places.
+         If unsure say N here.

 config SCHED_SMT
        bool "SMT scheduler support"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bd27b1cdac34..940eb1fe0abb 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1002,12 +1002,17 @@ config NR_CPUS
          to the kernel image.

 config SCHED_CLUSTER
+       def_bool y
+       prompt "Cluster scheduler support"
        help
         Cluster scheduler support improves the CPU scheduler's decision
+        making when dealing with machines that have clusters of CPUs.
+        Cluster usually means a couple of CPUs which are placed closely
+        by sharing mid-level caches, last-level cache tags or internal
+        busses. For example, on x86 Jacobsville, each 4 CPUs share one
+        L2 cache.
                        This feature isn't a universal win because it can bring
quoted
+        a cost of slightly increased overhead in some places. If unsure
+        say N here.
That is a really odd addition to a default-y feature.

How about I make both:

        help
          Cluster scheduler support improves the CPU scheduler's decision
          making when dealing with machines that have clusters of CPUs.
          Cluster usually means a couple of CPUs which are placed closely
          by sharing mid-level caches, last-level cache tags or internal
          busses.
looks good to me. thanks!

barry

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