From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8A5EE125AF; Mon, 5 Feb 2024 09:17:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707124673; cv=none; b=F6DGYpjywpHJkvD8CDW56cqyL8Rmkg+OyTOkn0cx6pxO6vepWLGk2oAFOb0awV0wHcSAXeZ4CvuYfqXaDCQltB368zDaYBtYhYA7/j4+JNGnyodUKP0xz8cCDqpaDSMr1zzYKksKRxwyg3DAxEEL1Sk8NhqcHmqpXZE0O7zNPTQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707124673; c=relaxed/simple; bh=XCbfBT5WPAPJsmmwuX3hRwQ/sWI5suce5+2EwKQixRQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EHSjSzJVFM1H6tPX9nbu/wZgfGHVEHNfRHK9kTFrga6tlI4wJX1Vg5pKxG2+OlFNSyHYnmvRdmt+ok/6EAnKVS/3gYBIl92Qxa78Udpn1q/yv6EMnjds9Y55IBykUUvhLOFmdalj1LSi94TIFGlms7kHZxaz2GOhyrNNn9ZO25k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1845C1FB; Mon, 5 Feb 2024 01:18:32 -0800 (PST) Received: from [10.1.32.28] (e133047.arm.com [10.1.32.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3A7BD3F5A1; Mon, 5 Feb 2024 01:17:48 -0800 (PST) Message-ID: <326b568d-d460-4a69-9336-28da328ffdcf@arm.com> Date: Mon, 5 Feb 2024 09:17:45 +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 Subject: Re: [PATCH] cpufreq: Change default transition delay to 2ms To: Qais Yousef , "Rafael J. Wysocki" , Viresh Kumar Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann References: <20240205022500.2232124-1-qyousef@layalina.io> Content-Language: en-US From: Christian Loehle In-Reply-To: <20240205022500.2232124-1-qyousef@layalina.io> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 05/02/2024 02:25, Qais Yousef wrote: > 10ms is too high for today's hardware, even low end ones. This default > end up being used a lot on Arm machines at least. Pine64, mac mini and > pixel 6 all end up with 10ms rate_limit_us when using schedutil, and > it's too high for all of them. > > Change the default to 2ms which should be 'pessimistic' enough for worst > case scenario, but not too high for platforms with fast DVFS hardware. > > Signed-off-by: Qais Yousef > --- > drivers/cpufreq/cpufreq.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 44db4f59c4cc..8207f7294cb6 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -582,11 +582,11 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy) > * for platforms where transition_latency is in milliseconds, it > * ends up giving unrealistic values. > * > - * Cap the default transition delay to 10 ms, which seems to be > + * Cap the default transition delay to 2 ms, which seems to be > * a reasonable amount of time after which we should reevaluate > * the frequency. > */ > - return min(latency * LATENCY_MULTIPLIER, (unsigned int)10000); > + return min(latency * LATENCY_MULTIPLIER, (unsigned int)(2*MSEC_PER_SEC)); > } > > return LATENCY_MULTIPLIER; Hi Qais, as previously mentioned I'm working on improving iowait boost and while I'm not against this patch per se it does make iowait boosting more aggressive. ((Doubling limited by rate_limit_us) Since the boost is often applied when not useful (for Android e.g. periodic f2fs writebacks), this might have some side effects. Please give me a couple of days for verifying any impact, or did you do that already? Kind Regards, Christian