From: Dave Hansen <dave.hansen@intel.com>
To: Rik van Riel <riel@surriel.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: kernel test robot <oliver.sang@intel.com>,
oe-lkp@lists.linux.dev, lkp@intel.com,
linux-kernel@vger.kernel.org, x86@kernel.org,
Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH v2] x86,mm: only trim the mm_cpumask once a second
Date: Tue, 3 Dec 2024 12:05:28 -0800 [thread overview]
Message-ID: <5544716d-31be-40c6-a289-030220e518de@intel.com> (raw)
In-Reply-To: <20241203144845.7093ea1a@fangorn>
On 12/3/24 11:48, Rik van Riel wrote:
> Sending TLB flush IPIs to CPUs that are in the mm_cpumask, but no
> longer running the program causes a regression in the will-it-scale
> tlbflush2 test. This test is contrived, but a large regression here
> might cause a small regression in some real world workload.
The patch seems OK in theory, but this explanation doesn't sit right
with me.
Most of the will-it-scale tests including tlbflush2 have long-lived
CPU-bound threads. They shouldn't schedule out much at all during the
benchmark. I don't see how they could drive a significant increase in
IPIs to cause a 10%+ regression.
I'd much prefer that we understand the regression in detail before
throwing more code at fixing it.
next prev parent reply other threads:[~2024-12-03 20:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-28 14:57 [tip:x86/mm] [x86/mm/tlb] 209954cbc7: will-it-scale.per_thread_ops 13.2% regression kernel test robot
2024-11-28 16:21 ` Peter Zijlstra
2024-11-29 1:44 ` Oliver Sang
2024-11-28 19:46 ` Mathieu Desnoyers
2024-11-29 2:52 ` Rik van Riel
2024-12-02 16:30 ` Mathieu Desnoyers
2024-12-02 18:10 ` Rik van Riel
2024-12-02 16:50 ` Dave Hansen
2024-12-03 0:43 ` [PATCH] x86,mm: only trim the mm_cpumask once a second Rik van Riel
2024-12-04 13:15 ` Oliver Sang
2024-12-04 16:07 ` Rik van Riel
2024-12-04 16:56 ` [PATCH v3] " Rik van Riel
2024-12-04 20:19 ` Mathieu Desnoyers
2024-12-05 2:03 ` [PATCH v4] " Rik van Riel
2024-12-06 1:30 ` Oliver Sang
2024-12-06 9:40 ` [tip: x86/mm] x86/mm/tlb: Only " tip-bot2 for Rik van Riel
2024-12-03 1:22 ` [PATCH -tip] x86,mm: only " Rik van Riel
2024-12-03 14:57 ` Mathieu Desnoyers
2024-12-03 19:48 ` [PATCH v2] " Rik van Riel
2024-12-03 20:05 ` Dave Hansen [this message]
2024-12-03 20:07 ` Rik van Riel
2024-12-04 0:46 ` Dave Hansen
2024-12-04 1:43 ` Rik van Riel
2024-12-03 23:27 ` Mathieu Desnoyers
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