From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fra-out-012.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-012.esa.eu-central-1.outbound.mail-perimeter.amazon.com [52.57.120.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD5F772614 for ; Wed, 17 Sep 2025 19:23:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.57.120.243 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758136993; cv=none; b=dQ6bKw8YW07Tl6+fMbAZyVvsSevmttBTUQJLnBGG8Orhtv5Su2iK0Xj225jqSB1tmNCpVyW0NspHOBCg3WfxCOoMSWz9LZSC2UyQnLrNxYJPHTq/Ly1FF/iLdi3Y1fGBKAunBspX4mxhyie6Rxzg2HBQthk7xxg1ehv2BvLlgOg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758136993; c=relaxed/simple; bh=JX9Ffh7Pf+hfk5UB6RHkGxi+gZ55byfAqIitgK2AQ28=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=CKEJnv1Aqgkb7huPE9xRbL5GlkPNL1xETZaoAeIWWZMbriZfVY4ZAIF5zu1UCLKQZQwuni+QJZRMw67yRMYR7XenHBf8dXflj62WqZ4fNlVnmFtjW9lGp/7TiFbg277AkagublxNgJaQfRefP8lG9bv8JYoZV+SPdzRb1fsiW5g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=h6VbFdwn; arc=none smtp.client-ip=52.57.120.243 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="h6VbFdwn" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1758136992; x=1789672992; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=JX9Ffh7Pf+hfk5UB6RHkGxi+gZ55byfAqIitgK2AQ28=; b=h6VbFdwn7ru297hcyIMuz4+upuX6Gg0TVPKi1UL9IaaDpRQ81bSbPivx 4d9TwQoSkWvegLzXRdxY8dEJ+PBH4LaP2/etcJSRQSekmLlA3TLMXDsYE puyqi+Z9ApFiA/nIGmU0SmAcdYBLvHAizWGuXZ5uYe5U8pCnWDuQ4ypIR HKjXUb8z+x7YWSfYcTl5q5+8YY6NI4xLndoors6Aw946JqkIrjvs5vLeK za8yRZdc7ojZSOxuIRSGEwdiWTldLTOFaf4aMNBXDhFRRv/uYSd2ZKzD2 zY3rc76FzjgDx9p/YvewTd+Jdja93dV/O48WpFLBD/R6+V8tlcwVsOm6p Q==; X-CSE-ConnectionGUID: CcJrk2DuSU2CcODOPrEeWg== X-CSE-MsgGUID: f1CS0OuBT5eB7gjJjNsuuQ== X-IronPort-AV: E=Sophos;i="6.18,272,1751241600"; d="scan'208";a="2172547" Received: from ip-10-6-3-216.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.3.216]) by internal-fra-out-012.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Sep 2025 19:23:01 +0000 Received: from EX19MTAEUA001.ant.amazon.com [54.240.197.233:4376] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.23.64:2525] with esmtp (Farcaster) id f3d28215-c9b9-4b1d-ac3e-07ff16a4cc00; Wed, 17 Sep 2025 19:23:01 +0000 (UTC) X-Farcaster-Flow-ID: f3d28215-c9b9-4b1d-ac3e-07ff16a4cc00 Received: from EX19D003EUB001.ant.amazon.com (10.252.51.97) by EX19MTAEUA001.ant.amazon.com (10.252.50.50) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Wed, 17 Sep 2025 19:22:53 +0000 Received: from u5934974a1cdd59.ant.amazon.com (10.146.13.227) by EX19D003EUB001.ant.amazon.com (10.252.51.97) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Wed, 17 Sep 2025 19:22:45 +0000 From: Fernand Sieber To: CC: , , , , , , , , , , , , , Subject: Re: [PATCH v2] sched/fair: Forfeit vruntime on yield Date: Wed, 17 Sep 2025 21:22:05 +0200 Message-ID: <20250917192205.2306162-1-sieberf@amazon.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250916140228.452231-1-sieberf@amazon.com> References: <20250916140228.452231-1-sieberf@amazon.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: EX19D046UWB003.ant.amazon.com (10.13.139.174) To EX19D003EUB001.ant.amazon.com (10.252.51.97) Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi Peter, I noticed you have pulled the change in sched/urgent. https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=78f8764d34c0a1912ce209bb2a428a94d062707f However, I'd appreciate if you could weigh in on my concern regarding this iteration not working well with core scheduling. Since the scheduler prefers to run the yielding task again regardless of its eligibility rather than putting the task in force idle, it can cause the yielding task vruntime to runaway quickly. This scenario causes severe run delays later on. Please see my previous reply with data supporting this concern. I think, the best approach to address it would be to clamp vruntime. I'm not sure how exactly, a simple approach would be to increment the vruntime by one slice until the task becomes ineligible, if you have any suggestions let me know. I'll run some testing soon when I get a chance. Thanks, Fernand Amazon Development Centre (South Africa) (Proprietary) Limited 29 Gogosoa Street, Observatory, Cape Town, Western Cape, 7925, South Africa Registration Number: 2004 / 034463 / 07