From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 087B449B451 for ; Thu, 8 Oct 2026 12:37:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791463053; cv=none; b=FWsW6tl2Mi6MB1AS2Qzcsj1X5J1KiRBIhrS1JSxmZZSeLvCt5oDugDoGFmx4rR8wDGRDg9lSsJ2cQ73JJsyMCeW7hdUmIuYpwixr7V0cYaCv9QtEKWaWqeT3fbUpjxp1bJNA37duwl1ORML2TO0RTQbx8g0pt/Xd0R1DARHbljs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791463053; c=relaxed/simple; bh=3YGRH66MEocHE8PHY3+X1AvHhNaJZ3N0ayOOhgWPQec=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sp24l18m4nWOQadHwRh2M3nTAQ8dpq24rsDD1M/6zm5mKmo/0+LP+nPX+EZVGQscOVSuGfLoS3visB+GvaECOzh+/NeguBiBO4fJExYYDG5isj7hZ+srRiQcEuXt1tSpWgTG8KjJC3chDqBFGJwek1zLPfK4a8x3+LdT6FebHJI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 0909668BEB; Thu, 8 Oct 2026 14:37:25 +0200 (CEST) Date: Thu, 8 Oct 2026 14:37:24 +0200 From: Christoph Hellwig To: John Garry Cc: Christoph Hellwig , kbusch@kernel.org, ahuang12@lenovo.com, sagi@grimberg.me, linux-nvme@lists.infradead.org, sunjw10@lenovo.com, iommu@lists.linux.dev Subject: Re: [PATCH] Revert "nvme-pci: clamp max_hw_sectors based on DMA optimized limitation" Message-ID: <20261008123724.GA22096@lst.de> References: <20261006120248.147654-1-hch@lst.de> <8cf8a8ea-c9c9-434b-aec6-e361280a88a4@linux.dev> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8cf8a8ea-c9c9-434b-aec6-e361280a88a4@linux.dev> User-Agent: Mutt/1.5.17 (2007-11-01) On Thu, Oct 08, 2026 at 08:36:54AM +0100, John Garry wrote: > On 10/6/26 13:02, Christoph Hellwig wrote: >> This turns down to cause up to 15% performance regressions on standard >> large transfer workloads. Revert it and hope the IOVA allocator can >> eventually be fixed to remove the need for the original workaround. >> >> This reverts commit 3710e2b056cb92ad816e4d79fa54a6a5b6ad8cbd. >> > > What was the block size and conditions for the original issue? The commit > just mentions that mdts=10 and we get a 4096KB max HW sectors. Good question. The original submitter and reporter are on Cc.