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Message-ID: <8bce19b2-37d9-4722-ba83-0088a4c9fc6a@linux.ibm.com>
Date: Thu, 28 Mar 2024 15:56:27 +0530
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Subject: Re: [RFC PATCH 0/1] sched/eevdf: Curb wakeup preemption further
To: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>, Ben Segall <bsegall@google.com>,
        Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira
 <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>, linux-kernel@vger.kernel.org,
        Tobias Huschle <huschle@linux.ibm.com>,
        Luis Machado <luis.machado@arm.com>, Chen Yu <yu.c.chen@intel.com>,
        Abel Wu <wuyun.abel@bytedance.com>,
        Tianchen Ding
 <dtcccc@linux.alibaba.com>,
        Youssef Esmat <youssefesmat@chromium.org>,
        Xuewen Yan <xuewen.yan94@gmail.com>,
        "Gautham R. Shenoy" <gautham.shenoy@amd.com>,
        Ingo Molnar
 <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>
References: <20240325060226.1540-1-kprateek.nayak@amd.com>
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Reply-To: 20240325060226.1540-1-kprateek.nayak@amd.com
From: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
In-Reply-To: <20240325060226.1540-1-kprateek.nayak@amd.com>
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Hi Prateek,

On 25/03/24 11:32, K Prateek Nayak wrote:
> Wakeup preemption problem
> =========================
> 
> With the curr entity's eligibility check, a wakeup preemption is very
> likely when an entity with positive lag joins the runqueue pushing the
> avg_vruntime of the runqueue backwards, making the vruntime of the
> current entity ineligible. This leads to aggressive wakeup preemption
> which was previously guarded by wakeup_granularity_ns in legacy CFS.

Is base_slice_ns not guarding it in EEVDF?

> Below figure depicts one such aggressive preemption scenario with EEVDF:

Thanks and Regards
Madadi Vineeth Reddy