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From: Roman Gushchin <roman.gushchin@linux.dev>
To: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: 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>, 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>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default
Date: Wed, 25 Jan 2023 18:02:04 -0800	[thread overview]
Message-ID: <Y9HfHKXRPLrfG6g1@P9FQF9L96D.corp.robot.car> (raw)
In-Reply-To: <20230121033942.350387-1-42.hyeyoo@gmail.com>

On Sat, Jan 21, 2023 at 12:39:42PM +0900, Hyeonggon Yoo wrote:
> 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>

Nice!

I checkout my very simple kmem performance test (1M allocations 8-bytes allocations)
and it shows ~30% difference: 112319 us with vs 80836 us without.

Probably not that big for real workloads, but still nice to have.

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Thank you!

  parent reply	other threads:[~2023-01-26  2:02 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-21  3:39 [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default Hyeonggon Yoo
2023-01-21 11:29 ` 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 [this message]
2023-01-27 11:45   ` Hyeonggon Yoo
2023-02-02  3:09 ` Davidlohr Bueso

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