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authorHyeonggon Yoo <42.hyeyoo@gmail.com>2023-01-21 06:39:42 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-02-03 09:50:10 +0300
commitcc6003916ed46d7a67d91ee32de0f9138047d55f (patch)
tree2fa539d0569ab251077af26f69b12321e109539b /lib/Kconfig.debug
parentf65c35d3336ec8c7af6e12b7fd15acfb4b8e9ffa (diff)
downloadlinux-cc6003916ed46d7a67d91ee32de0f9138047d55f.tar.xz
lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default
In workloads where this_cpu operations are frequently performed, enabling DEBUG_PREEMPT may result in significant increase in runtime overhead due to frequent invocation of __this_cpu_preempt_check() function. This can be demonstrated through benchmarks such as hackbench where this configuration results in a 10% reduction in performance, primarily due to the added overhead within memcg charging path. Therefore, do not to enable DEBUG_PREEMPT by default and make users aware of its potential impact on performance in some workloads. hackbench-process-sockets debug_preempt no_debug_preempt Amean 1 0.4743 ( 0.00%) 0.4295 * 9.45%* Amean 4 1.4191 ( 0.00%) 1.2650 * 10.86%* Amean 7 2.2677 ( 0.00%) 2.0094 * 11.39%* Amean 12 3.6821 ( 0.00%) 3.2115 * 12.78%* Amean 21 6.6752 ( 0.00%) 5.7956 * 13.18%* Amean 30 9.6646 ( 0.00%) 8.5197 * 11.85%* Amean 48 15.3363 ( 0.00%) 13.5559 * 11.61%* Amean 79 24.8603 ( 0.00%) 22.0597 * 11.27%* Amean 96 30.1240 ( 0.00%) 26.8073 * 11.01%* Link: https://lkml.kernel.org/r/20230121033942.350387-1-42.hyeyoo@gmail.com Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Ben Segall <bsegall@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Pekka Enberg <penberg@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Steven Rostedt (Google) <rostedt@goodmis.org> Cc: Tejun Heo <tj@kernel.org> Cc: Valentin Schneider <vschneid@redhat.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'lib/Kconfig.debug')
-rw-r--r--lib/Kconfig.debug5
1 files changed, 4 insertions, 1 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 918bda4ee120..a97aca81db24 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1246,13 +1246,16 @@ config DEBUG_TIMEKEEPING
config DEBUG_PREEMPT
bool "Debug preemptible kernel"
depends on DEBUG_KERNEL && PREEMPTION && TRACE_IRQFLAGS_SUPPORT
- default y
help
If you say Y here then the kernel will use a debug variant of the
commonly used smp_processor_id() function and will print warnings
if kernel code uses it in a preemption-unsafe way. Also, the kernel
will detect preemption count underflows.
+ This option has potential to introduce high runtime overhead,
+ depending on workload as it triggers debugging routines for each
+ this_cpu operation. It should only be used for debugging purposes.
+
menu "Lock Debugging (spinlocks, mutexes, etc...)"
config LOCK_DEBUGGING_SUPPORT