From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fra-out-010.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-010.esa.eu-central-1.outbound.mail-perimeter.amazon.com [63.178.143.178]) (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 C75EA40756B for ; Wed, 4 Feb 2026 12:46:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=63.178.143.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770209167; cv=none; b=hfOjvuYv5r86lmRkUiemtKheKl7E+UJsRhn5mhQEax9NXvZ5QxDotxN46HseXlr+BUKrB5cGE78Es6g7CKnYbK1+EoqcaAcIMAV7DNnD4lq+UmWEjh2xlPZ0nuNDQ2LZlcDqHsuI9pPcNItCjBu5+jlQ2ZRbqJtKHK8wViHmDPU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770209167; c=relaxed/simple; bh=hcZ9HQSaOoejsYOBFZ/8dvfK7XctRusOw3bqeZatz/w=; h=Subject:Message-ID:Date:MIME-Version:From:To:CC:References: In-Reply-To:Content-Type; b=qEm13BDQs3XRO0p6VO8zRH33mGPTPrJWYw34LBLiwqBdL3zxqh9xIujlKGmq5lxWMGXg4z6m/AZpD0WtOKFfOVm7fbKjX/afUZsNvFvYbfL4o1QO6JmB1gKeOggnsiKMgTcZEAZr55qmCd3B4wD4uiRLEOCraHCeE7wmy1lwJTk= 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=tvYv9bF2; arc=none smtp.client-ip=63.178.143.178 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="tvYv9bF2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1770209167; x=1801745167; h=message-id:date:mime-version:from:to:cc:references: in-reply-to:content-transfer-encoding:subject; bh=bghazjdt7CUSgI/rG6C70rm7Sg/fqr0J8OEDH8aYGMU=; b=tvYv9bF2QHsXFcYY2Uzb+c2nWCzrUUA6cizkWcCjQgaNG9oyYsQiEIFh bgOvfYfAXr84ssQQS+ARbJSAVYzCv5cHjhRQQnuIG+D93RKxIL5NudiA4 iuAOBtKQcVePsjZWS4mpK7JwIzUb/Mj8LFpNzd3KbpBGpip8gvxMvoZoE bgJwrhw5MODgOhqHncg/MlO8HPRG+TU8zrH9psB7XDzmDArlWEgF0zv7t /ZjMbb9FBy9BtlEQ3e/oUwncgUXyANvn0BDpphBjyDJ8khJElPEICevN9 Sybu5wAIxNcdt4ccj+Jy8440AWqx5afsL95fB/rpOYhPsmNBttQW5KcuY A==; X-CSE-ConnectionGUID: KDoOIMHhQLmhd/VmejSChQ== X-CSE-MsgGUID: 1lIM8M9gS+ydMcjpQ6ZLDA== X-IronPort-AV: E=Sophos;i="6.21,272,1763424000"; d="scan'208";a="8819934" Subject: Re: [PATCH 4/4] sched/fair: Proportional newidle balance Received: from ip-10-6-6-97.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.6.97]) by internal-fra-out-010.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Feb 2026 12:45:47 +0000 Received: from EX19MTAEUB002.ant.amazon.com [54.240.197.224:5326] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.30.239:2525] with esmtp (Farcaster) id 737b1c55-5ef5-41f8-bfd4-bc9db6b14dba; Wed, 4 Feb 2026 12:45:47 +0000 (UTC) X-Farcaster-Flow-ID: 737b1c55-5ef5-41f8-bfd4-bc9db6b14dba Received: from EX19D018EUA004.ant.amazon.com (10.252.50.85) by EX19MTAEUB002.ant.amazon.com (10.252.51.79) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Wed, 4 Feb 2026 12:45:42 +0000 Received: from [192.168.1.220] (10.106.83.33) by EX19D018EUA004.ant.amazon.com (10.252.50.85) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.35; Wed, 4 Feb 2026 12:45:42 +0000 Message-ID: Date: Wed, 4 Feb 2026 12:45:41 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: "Mohamed Abuelfotoh, Hazem" To: Peter Zijlstra CC: Mario Roy , Chris Mason , "Joseph Salisbury" , Adam Li , Josh Don , , , , , , , , , References: <20251107160645.929564468@infradead.org> <20251107161739.770122091@infradead.org> <8760001e-0274-454c-a4e4-1f38a9695b88@gmail.com> <3ef2a178-db96-4a2c-9e74-44ba81bef030@amazon.com> <20260127084412.GV171111@noisy.programming.kicks-ass.net> <20260129091937.GY166857@noisy.programming.kicks-ass.net> <683b4860-1076-43b8-8fb9-ca8ac26cd8f4@amazon.com> <20260202105144.GC1282955@noisy.programming.kicks-ass.net> <6237f4ee-6b07-4d79-8ee7-04e49a4e99b7@amazon.com> Content-Language: en-US In-Reply-To: <6237f4ee-6b07-4d79-8ee7-04e49a4e99b7@amazon.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: EX19D007EUB001.ant.amazon.com (10.252.51.82) To EX19D018EUA004.ant.amazon.com (10.252.50.85) On 02/02/2026 11:07, Mohamed Abuelfotoh, Hazem wrote: > On 02/02/2026 10:51, Peter Zijlstra wrote: >> >> OK, that clarifies. >> >> How does the NI_RATE patch work for you? >> >>    https://lkml.kernel.org/ >> r/20260127151748.GA1079264@noisy.programming.kicks-ass.net > > Sure I am going to apply this patch and report the results. > > > I have tested the patch proposed in [1] on top of v6.12.66 and unfortunately I haven't seen any improvement. I mainly compared the results between v6.12.66 & v6.12.66_revert_1b9c118fe318 which has the revert for 1b9c118fe318 ("sched/fair: Proportional newidle balance") and v6.12.66_proposed which is v6.12.66 + the patch proposed in [1]. I mainly focused on AMD based c7a.4xlarge which was highly impacted as previously discussed in this thread. The baseline is v6.12.66_revert_1b9c118fe318 as it showed the best performance among the other available kernel options. Version | Benchmark name | SUT EC2 Instance| diff % v6.12.66 | postgresql | c7a.4xlarge | -4.0% v6.12.66 | nginx_lb | c7a.4xlarge | -5.0% v6.12.66 | memcached | c7a.4xlarge | -11.0% v6.12.66_proposed | postgresql | c7a.4xlarge | -4.0% v6.12.66_proposed | nginx_lb | c7a.4xlarge | -5.0% v6.12.66_proposed | memcached | c7a.4xlarge | -13.0% Furthermore We have also seen around 10-20% randwrite fio performance regression on v6.18.5 only on AMD based VMs. We confirmed that this regression is caused by 1b9c118fe318 ("sched/fair: Proportional newidle balance"). We are currently testing if the patch proposed in [1] to see if it will help with this regression and will be sharing the results & reproduction steps and environment in the next update. [1 https://lkml.kernel.org/r/20260127151748.GA1079264@noisy.programming.kicks-ass.net