From: Greg Kroah-Hartman Date: Fri, 20 Oct 2023 06:13:44 +0000 (+0200) Subject: 5.15-stable patches X-Git-Tag: v4.14.328~127 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=20bf71720f5b081bd286239c0776a86eaa7f3e20;p=thirdparty%2Fkernel%2Fstable-queue.git 5.15-stable patches added patches: lib-kconfig.debug-do-not-enable-debug_preempt-by-default.patch series --- diff --git a/queue-5.15/lib-kconfig.debug-do-not-enable-debug_preempt-by-default.patch b/queue-5.15/lib-kconfig.debug-do-not-enable-debug_preempt-by-default.patch new file mode 100644 index 00000000000..b0d84757c7d --- /dev/null +++ b/queue-5.15/lib-kconfig.debug-do-not-enable-debug_preempt-by-default.patch @@ -0,0 +1,85 @@ +From cc6003916ed46d7a67d91ee32de0f9138047d55f Mon Sep 17 00:00:00 2001 +From: Hyeonggon Yoo <42.hyeyoo@gmail.com> +Date: Sat, 21 Jan 2023 12:39:42 +0900 +Subject: lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default + +From: Hyeonggon Yoo <42.hyeyoo@gmail.com> + +commit cc6003916ed46d7a67d91ee32de0f9138047d55f upstream. + +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 +Acked-by: Mel Gorman +Acked-by: Davidlohr Bueso +Cc: Ben Segall +Cc: Christoph Lameter +Cc: Daniel Bristot de Oliveira +Cc: David Rientjes +Cc: Dennis Zhou +Cc: Dietmar Eggemann +Cc: Ingo Molnar +Cc: Johannes Weiner +Cc: Joonsoo Kim +Cc: Juri Lelli +Cc: Matthew Wilcox +Cc: Muchun Song +Cc: Pekka Enberg +Cc: Peter Zijlstra +Cc: Shakeel Butt +Cc: Steven Rostedt (Google) +Cc: Tejun Heo +Cc: Valentin Schneider +Cc: Vincent Guittot +Cc: Vlastimil Babka +Signed-off-by: Andrew Morton +Cc: Luiz Capitulino +Signed-off-by: Greg Kroah-Hartman +--- + lib/Kconfig.debug | 5 ++++- + 1 file changed, 4 insertions(+), 1 deletion(-) + +--- a/lib/Kconfig.debug ++++ b/lib/Kconfig.debug +@@ -1226,13 +1226,16 @@ 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 diff --git a/queue-5.15/series b/queue-5.15/series new file mode 100644 index 00000000000..3b34f9c4342 --- /dev/null +++ b/queue-5.15/series @@ -0,0 +1 @@ +lib-kconfig.debug-do-not-enable-debug_preempt-by-default.patch