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| author | Hyeonggon Yoo <42.hyeyoo@gmail.com> | 2023-01-21 12:39:42 +0900 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-02 22:50:10 -0800 |
| commit | cc6003916ed46d7a67d91ee32de0f9138047d55f (patch) | |
| tree | 2fa539d0569ab251077af26f69b12321e109539b /lib/Kconfig.debug | |
| parent | f65c35d3336ec8c7af6e12b7fd15acfb4b8e9ffa (diff) | |
| download | lwn-cc6003916ed46d7a67d91ee32de0f9138047d55f.tar.gz lwn-cc6003916ed46d7a67d91ee32de0f9138047d55f.zip | |
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.debug | 5 |
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 |