From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 1858C19DF93 for ; Mon, 24 Jun 2024 16:33:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719246823; cv=none; b=gzKaX6VAny5wdxBtpPeVvjktsT+dbMeMmRII8aV1NlyY5defTtBTZ8BBCiXUUORo4vTIuCTNRqnNaz59M3pym4F5jC8LFpnd1TwwzhnzzWHM2Yakl1BF4iLVsgPLVHm1/PINMBAXpadtrcPYdusC+rhtjJez9jV+5ohtK3fwOeg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719246823; c=relaxed/simple; bh=4gqQAbOK79zS1uKAm/hj5eq4OIA6n71bJj1tEIJvkBY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=V/TKxphIdddjjsXXp3SqgRZS7gcFbwIcwIDf/LVgxNKLUNXX3Mu2RItQLLYhNZ7taDJvmAGzpj/75xAsbK2i6P1NUx8LgS9yOv9ffT6jmcf75OMBOOMYmJXIaTjpqZuN/ZwT/Ix1WFMNpcA/AcXjFeQS4Ix3H0sCcWyUyB9GZ1I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Yrun7rfc; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Yrun7rfc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719246820; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dgN0dBgy6sR0oAWnnFjEXlGg9ErnyA+uGyeQrtdxBG8=; b=Yrun7rfcH9rN+dBPsXPupt07jHbO0UgtDO7dCee1Z95BNLXdSQAaSRAFLVSHRgn+SwWU7s 246Z1CvWswd9qUmUTVO0d1x0wHj55E+ScclUpQH/1j/mau5I+gd2G9179gbOhYXD1VJLhY oF4I3z/FeM8YRNX4HRgg3DDyZcbrIAE= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-106-hyTBx4oRNMyFE2NshUZ6sw-1; Mon, 24 Jun 2024 12:33:34 -0400 X-MC-Unique: hyTBx4oRNMyFE2NshUZ6sw-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EA53F1955E82; Mon, 24 Jun 2024 16:33:31 +0000 (UTC) Received: from [10.22.17.135] (unknown [10.22.17.135]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id DC0AB19560BF; Mon, 24 Jun 2024 16:33:28 +0000 (UTC) Message-ID: Date: Mon, 24 Jun 2024 12:33:27 -0400 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] memcg: Add a new sysctl parameter for automatically setting memory.high To: Roman Gushchin Cc: Johannes Weiner , Michal Hocko , Muchun Song , Andrew Morton , Jonathan Corbet , Shakeel Butt , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Alex Kalenyuk , Peter Hunt , linux-doc@vger.kernel.org References: <20240623204514.1032662-1-longman@redhat.com> <77d4299e-e1ee-4471-9b53-90957daa984d@redhat.com> Content-Language: en-US From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On 6/24/24 11:21, Roman Gushchin wrote: > On Sun, Jun 23, 2024 at 04:52:00PM -0400, Waiman Long wrote: >> Correct some email addresses. >> >> On 6/23/24 16:45, Waiman Long wrote: >>> With memory cgroup v1, there is only a single "memory.limit_in_bytes" >>> to be set to specify the maximum amount of memory that is allowed to >>> be used. So a lot of memory cgroup using tools and applications allow >>> users to specify a single memory limit. When they migrate to cgroup >>> v2, they use the given memory limit to set memory.max and disregard >>> memory.high for the time being. >>> >>> Without properly setting memory.high, these user space applications >>> cannot make use of the memory cgroup v2 ability to further reduce the >>> chance of OOM kills by throttling and early memory reclaim. >>> >>> This patch adds a new sysctl parameter "vm/memory_high_autoset_ratio" >>> to enable setting "memory.high" automatically whenever "memory.max" is >>> set as long as "memory.high" hasn't been explicitly set before. This >>> will allow a system administrator or a middleware layer to greatly >>> reduce the chance of memory cgroup OOM kills without worrying about >>> how to properly set memory.high. >>> >>> The new sysctl parameter will allow a range of 0-100. The default value >>> of 0 will disable memory.high auto setting. For any non-zero value "n", >>> the actual ratio used will be "n/(n+1)". A user cannot set a fraction >>> less than 1/2. > Hi Waiman, > > I'm not sure that setting memory.high is always a good idea (it comes > with a certain cost, e.g. can increase latency), but even if it is, > why systemd or similar userspace tools can't do this? We actually have a OOM problem with OpenShift which is based on Kubernetes. AFAIK, the setting of memory.high is still in alpha for Kubernetes. So a memory cgroup is set up just by setting memory.max at the moment. I also trace back the OOM problem to commit 14aa8b2d5c2e ("mm/mglru: don't sync disk for each aging cycle") in the MGLRU code. So setting memory.high automatically is one way to avoid premature OOM. That is the motivation behind this patch. > > I wonder what's special about your case if you do see a lot of OOMs > which can be avoided by setting memory.high? Do you have a bursty workload? In our case, the OOM kill can be triggered by writing a large data file that exceeds memory.max to a NFS mounted filesystem as long as there is enough free pages that the dirty_bytes/dirty_background_bytes mechanism isn't triggered. Regards, Longman