From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 6C9ED1E7C23; Tue, 11 Nov 2025 09:29:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762853399; cv=none; b=U1sSg5kotPQk6KeSVdW/ZkLraGFJIHDoccgl2mooKQVeAJwmEppvuXt6vQ/tm3sz/+11PAFbIYW+mnrHYlJHki5xjMMVZ4KDvt5QBVwVUOm1BtPNlf6i0AThouXXChInNblZSO8VzC5GjrfVu5uc4ZXZu3K/TOlW8NLutix+jQQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762853399; c=relaxed/simple; bh=kaLucZEJ4YS1HPett39SZpYnsQ4TXu9CRYgVRxQfXSI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=u+eadCTOWHJK7YyHcbpcxxR1knUWHmWBS8Wj919kELJjqAqE/Tv9TajsFBbfQtguRv7iS1GcUOB04/NeYjOCJwKHmX8cALOX1An1twS6Sj305mKObethEuD/jlgs9zX3jDHGaaANds2EJ0RZWDKOg3+VqgJMdkIr0xgIEKqc1Uc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=NAyRmNsj; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="NAyRmNsj" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KOGX5U0hIAV8DLXo2ghwwdTEcIHxrAEQiaVG4VywUq0=; b=NAyRmNsjZkRkIWiWoC71wwR339 8aZgDfavsFm/PpXTrxT4xxEaZvErUrMZZkXuAjFOjJ3FPrZvf337Q5d5Cavz2QmzslqrqcpnMBqY6 crOhAwCRpVV/Vc1L9hCyRPzzzlBFhrMdd/AfwI7seYEBKToO7Iud6FxUfe6pmiogHRvWDYEaZXntB sfzMoPfDa1JHxg7dB0PEVD0wKcMdfBtI0PlLjwmNyZPPJ4lz7DXEzt/dO7ParMSKFVNhfT3CmlEsE I70ztMaBa35J/uA/7MHEiOB2CUlzpdyxY/oYujvwXS/DR7dTGOTySHwdLWfsd8dLjbnr0rOVYBUmD g5eSkn6Q==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIkhJ-00000006qU3-2XKW; Tue, 11 Nov 2025 09:29:57 +0000 Date: Tue, 11 Nov 2025 01:29:57 -0800 From: Christoph Hellwig To: John Garry Cc: "Darrick J. Wong" , zlang@redhat.com, fstests@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [PATCH 6/7] generic/774: reduce file size Message-ID: References: <176279908967.605950.2192923313361120314.stgit@frogsfrogsfrogs> <176279909116.605950.12144124358096086284.stgit@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Nov 11, 2025 at 09:13:27AM +0000, John Garry wrote: > On 10/11/2025 18:27, Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > We've gotten complaints about this test taking hours to run and > > producing stall warning on test VMs with a large number of cpu cores. I > > think this is due to the maximum atomic write unit being very large on > > XFS where we can fall back to a software-based out of place write > > implementation. > > > > On the victim machine, the atomic write max is 4MB and there are 24 > > CPUs. As a result, aw_bsize to be 1MB, so the file size is > > 1MB * 24 * 2 * 100 == 4.8GB. I set up a test machine with fast storage > > and 24 CPUs, and the atomic writes poked along at 25MB/s and the total > > runtime was 300s. On spinning rust those stats will be much worse. > > > > Let's try backing the file size off by 10x and see if that eases the > > complaints. > > > > The awu max for xfs is still unbounded (so the file size could still be > huge). For ext4, it is limited by HW constraints - the largest HW awu max I > heard about is 256KB. How about also limiting awu max to something sane, > like 1MB? Sounds fine to ne, as long as we document it as an arbitrary limit.