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 55F425387 for ; Wed, 30 Aug 2023 11:54:35 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 39C3F67373; Wed, 30 Aug 2023 13:54:31 +0200 (CEST) Date: Wed, 30 Aug 2023 13:54:31 +0200 From: Christoph Hellwig To: Robin Murphy Cc: Christoph Hellwig , m.szyprowski@samsung.com, yajun.deng@linux.dev, iommu@lists.linux.dev Subject: Re: [PATCH] dma-contiguous: fix the Kconfig entry for CONFIG_DMA_NUMA_CMA Message-ID: <20230830115431.GA23190@lst.de> References: <20230830092731.148759-1-hch@lst.de> 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: User-Agent: Mutt/1.5.17 (2007-11-01) On Wed, Aug 30, 2023 at 11:11:29AM +0100, Robin Murphy wrote: > I think the "good reason" is that folks who do have NUMA systems are likely > to be more interested in getting more consistent DMA performance than > losing a bit more non-movable memory capacity, and the runtime impact on > non-NUMA systems should be negligible, so I would definitely be inclined to > make it "default y". But it's not critically important. Well, Linus hates these default y, and usually for a good reason. If it's that useful/importanst for numa systems we should just drop the option and make the code conditional on CONFIG_NUMA only.