1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 590a27fc212f..f78eab251897 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -192,6 +192,7 @@ config IRQSOFF_TRACER
         select TRACER_MAX_TRACE
         select RING_BUFFER_ALLOW_SWAP
         select TRACER_SNAPSHOT
+        select TRACER_SNAPSHOT_PER_CPU_SWAP
         help
           This option measures the time spent in irqs-off critical
           sections, with microsecond accuracy.
@@ -215,6 +216,7 @@ config PREEMPT_TRACER
         select TRACER_MAX_TRACE
         select RING_BUFFER_ALLOW_SWAP
         select TRACER_SNAPSHOT
+        select TRACER_SNAPSHOT_PER_CPU_SWAP
         help
           This option measures the time spent in preemption-off critical
           sections, with microsecond accuracy.
@@ -266,6 +268,27 @@ config TRACER_SNAPSHOT
               echo 1 > /sys/kernel/debug/tracing/snapshot
               cat snapshot
 
+config TRACER_SNAPSHOT_PER_CPU_SWAP
+        bool "Allow snapshot to swap per CPU"
+        depends on TRACER_SNAPSHOT
+        select RING_BUFFER_ALLOW_SWAP
+        help
+          Allow doing a snapshot of a single CPU buffer instead of a
+          full swap (all buffers). If this is set, then the following is
+          allowed:
+
+              echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
+
+          After which, only the tracing buffer for CPU 2 was swapped with
+          the main tracing buffer, and the other CPU buffers remain the same.
+
+          When this is enabled, this adds a little more overhead to the
+          trace recording, as it needs to add some checks to synchronize
+          recording with swaps. But this does not affect the performance
+          of the overall system. This is enabled by default when the preempt
+          or irq latency tracers are enabled, as those need to swap as well
+          and already adds the overhead (plus a lot more).
+
 config TRACE_BRANCH_PROFILING
         bool
         select GENERIC_TRACER