From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Vlastimil Babka <vbabka@suse.cz>,
Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ingo Molnar <mingo@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Shakeel Butt <shakeelb@google.com>,
Muchun Song <muchun.song@linux.dev>,
Matthew Wilcox <willy@infradead.org>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default
Date: Sat, 21 Jan 2023 12:39:42 +0900 [thread overview]
Message-ID: <20230121033942.350387-1-42.hyeyoo@gmail.com> (raw)
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%*
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
lib/Kconfig.debug | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ddbfac2adf9c..f6f845a4b9ec 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1176,13 +1176,16 @@ 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
--
2.34.1
next reply other threads:[~2023-01-21 3:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-21 3:39 Hyeonggon Yoo [this message]
2023-01-21 11:29 ` [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default Vlastimil Babka
2023-01-21 11:54 ` Hyeonggon Yoo
2023-01-23 8:58 ` Michal Hocko
2023-01-25 15:41 ` Hyeonggon Yoo
2023-01-25 9:51 ` Michal Hocko
2023-01-27 11:43 ` Hyeonggon Yoo
2023-01-27 12:33 ` Michal Hocko
2023-01-23 11:05 ` Christoph Lameter
2023-01-24 16:34 ` Hyeonggon Yoo
2023-01-23 14:01 ` Mel Gorman
2023-01-26 2:02 ` Roman Gushchin
2023-01-27 11:45 ` Hyeonggon Yoo
2023-02-02 3:09 ` Davidlohr Bueso
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230121033942.350387-1-42.hyeyoo@gmail.com \
--to=42.hyeyoo@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mingo@redhat.com \
--cc=muchun.song@linux.dev \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
--cc=roman.gushchin@linux.dev \
--cc=shakeelb@google.com \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).