From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 043B5CFD646 for ; Wed, 7 Jan 2026 14:42:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 39B676B0088; Wed, 7 Jan 2026 09:42:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 373236B0092; Wed, 7 Jan 2026 09:42:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2A96D6B0095; Wed, 7 Jan 2026 09:42:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 1B7C46B0088 for ; Wed, 7 Jan 2026 09:42:50 -0500 (EST) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id C09601B1EA for ; Wed, 7 Jan 2026 14:42:49 +0000 (UTC) X-FDA: 84305434458.20.B6D0D95 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf16.hostedemail.com (Postfix) with ESMTP id 40427180008 for ; Wed, 7 Jan 2026 14:42:48 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=lst.de; spf=pass (imf16.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1767796968; a=rsa-sha256; cv=none; b=0PvxvqP97ax6qoKAM0gehNErpghOjjTi/DA+vOydPJ+owcUCcNfQ82FnCC2m+bjorOWh00 G6gMgGbeLhgMyIkxWEpVI8cnqCbNFq4s53PgxDOPmKbToOwgscwBMiupE+B3FjcIvFdenm lVZqWL2XdpszlYd/1cDINgFJQ1lE3vM= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=lst.de; spf=pass (imf16.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767796968; h=from:from:sender: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: in-reply-to:in-reply-to:references:references; bh=f0wWC8TE/hWdr1e40O7JPX4+48/35Q8yjX+wJXDlvlQ=; b=Zj2hGx9e6uPt1vdR3NXah3746eTq0xL+Pro3UBebXXC6eHHqm0B5CiJkMeH20n5i497nou t3PkinnbTA7QxHPWQ1buYXX3QtW4Nj/Wghz4UkqgCTZlAlAvBq4IjkXwApJ1Kdxz71zIRX LRCcV7zwCW/YD5hGcotAsqI7DAiNvrc= Received: by verein.lst.de (Postfix, from userid 2407) id 45DFD227AAA; Wed, 7 Jan 2026 15:42:44 +0100 (CET) Date: Wed, 7 Jan 2026 15:42:43 +0100 From: Christoph Hellwig To: Chuck Lever Cc: Christoph Hellwig , Mike Snitzer , linux-nfs@vger.kernel.org, Chuck Lever , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH 1/2] NFSD: Add aggressive write throttling control Message-ID: <20260107144243.GA15228@lst.de> References: <20251219141105.1247093-1-cel@kernel.org> <20251219141105.1247093-2-cel@kernel.org> <20260107075501.GA19005@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 40427180008 X-Stat-Signature: gw4aymw8cz4m56419m6ps6cshoft4owo X-HE-Tag: 1767796968-134346 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jan 07, 2026 at 09:36:39AM -0500, Chuck Lever wrote: > > What makes NFSD so special here vs say a userspace process with a bunch > > of threads? Also what is the actual problem we're trying to solve? > > The problem, as I see it, is that the system is not providing enough > backpressure to slow down noisy clients, allowing them to overwhelm > the server's memory with UNSTABLE WRITE traffic. > > This is the same issue, IMO, that Mike's direct I/O is attempting to > address. Our implementation of UNSTABLE WRITE is a denial-of-service > vector. But how is this different from Samba or a userspace NFS server?