From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp134-31.sina.com.cn (smtp134-31.sina.com.cn [180.149.134.31]) (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 DB1CE12B17C for ; Mon, 9 Sep 2024 10:52:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=180.149.134.31 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725879181; cv=none; b=CFzC+Rvqbad8cy8JdYNMx6u7IUkjwPw/qXL0Biq6W4C4ka+u9x+YYZMkWFgKC8FZgETew3a5S99ePbsXgNjhcoq4gqIFSjK/TDu/MPP6/ErVdTM+QP7CpUbXFrrpOJgXlJikhuxo8sHc1jmu1r7jI59+ZTQHIRhKEYu7dj0TC9o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725879181; c=relaxed/simple; bh=k6rzkPhOo6lj4rSMToLU4dfqNi1A2723OsN/cGNSVqI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=E1Vn3/Umn5eOXGcuYqxCCZ4S5eeQxYR3s+W5NeS4+fcvV82rUBGIuabse+sv9Sui6yCdupmvasroikFnjnYKTpjxAXLuZQ6EKPMlhSISYCAHx7inZNx/b5SZJcwOkGAL6WB0N9+aHY247mk2nsQWKIbQIUkn/V+LvIUhFeanrBo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sina.com; spf=pass smtp.mailfrom=sina.com; arc=none smtp.client-ip=180.149.134.31 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([113.88.50.122]) by sina.com (10.185.250.21) with ESMTP id 66DED35700006845; Mon, 9 Sep 2024 18:52:10 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 9132623408182 X-SMAIL-UIID: E5A1A39DA601451EA2E93BE98ABAF976-20240909-185210-1 From: Hillf Danton To: Michal Hocko Cc: Davidlohr Bueso , yosryahmed@google.com, Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -next] mm: introduce per-node proactive reclaim interface Date: Mon, 9 Sep 2024 18:51:57 +0800 Message-Id: <20240909105157.2663-1-hdanton@sina.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Date: Mon, 9 Sep 2024 09:12:03 +0200 Michal Hocko > On Fri 06-09-24 19:04:19, Hillf Danton wrote: > > On Thu, 5 Sep 2024 16:29:41 -0700 Davidlohr Bueso > > > On Fri, 06 Sep 2024, Hillf Danton wrote:\n > > > >The proactive reclaim on the cmdline looks like waste of cpu cycles before > > > >the cases where kswapd fails to work are spotted. It is not correct to add > > > >it because you can type the code. > > > > > > Are you against proactive reclaim altogether (ie: memcg) or this patch in > > > particular, which extends its availability? > > > > > The against makes no sense to me because I know your patch is never able to > > escape standing ovation. > > I fail to understand your reasoning. Do you have any actual technical > arguments why this is a bad idea? > > > > The benefits of proactive reclaim are well documented, and the community has > > > been overall favorable towards it. This operation is not meant to be generally > > > used, but there are real latency benefits to be had which are completely > > > unrelated to watermarks. Similarly, we have 'compact' as an alternative to > > > kcompactd (which was once upon a time part of kswapd). > > > > > Because kswapd is responsible for watermark instead of high order pages, > > compact does not justify proactive reclaim from the begining. > > What do you mean? How does keeping a global watermark helps to trigger > per NUMA node specific aging - e.g. demotion? > In addition to the cost of pro/demorion, the percpu pages prevent random aging from making any sense without memory pressue, because I think it is aging that rolls out red carpet for multi-gen lru.