From: Peter Zijlstra <peterz@infradead.org>
To: kernel test robot <oliver.sang@intel.com>
Cc: Fernand Sieber <sieberf@amazon.com>,
oe-lkp@lists.linux.dev, lkp@intel.com,
linux-kernel@vger.kernel.org, aubrey.li@linux.intel.com,
yu.c.chen@intel.com, Ingo Molnar <mingo@kernel.org>
Subject: Re: [linus:master] [sched/fair] 79104becf4: stress-ng.resched.ops_per_sec 44.6% regression
Date: Fri, 12 Dec 2025 11:12:44 +0100 [thread overview]
Message-ID: <20251212101244.GN3911114@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <202512112111.39299a7e-lkp@intel.com>
On Thu, Dec 11, 2025 at 10:21:15PM +0800, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed a 44.6% regression of stress-ng.resched.ops_per_sec on:
>
>
> commit: 79104becf42baeeb4a3f2b106f954b9fc7c10a3c ("sched/fair: Forfeit vruntime on yield")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
After nearly 2 decades of telling people that using yield() is UB
(except in the Real-Time cases where it is well defined), I'm >.< close
to not caring about this.
IIRC this benchmark is literally something like running yield() in a
loop, so boohoo. I'll look when there's a real workload that has a
problem.
> [still regression on linus/master cfd4039213e7b5a828c5b78e1b5235cac91af53d]
> [still regression on linux-next/master 82bcd04d124a4d84580ea4a8ba6b120db5f512e7]
What's with the still? AFAIK this is the first report of this.
next prev parent reply other threads:[~2025-12-12 10:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-11 14:21 [linus:master] [sched/fair] 79104becf4: stress-ng.resched.ops_per_sec 44.6% regression kernel test robot
2025-12-12 10:12 ` Peter Zijlstra [this message]
2025-12-16 2:42 ` Oliver Sang
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