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 C3AE817BB2E; Wed, 20 Nov 2024 09:37:18 +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=1732095441; cv=none; b=ffAeohE+B2qTmp0IQfkuyqE/SdvACgUsKr1DUcL25FNpaFv/cB7WGd2xmzkaRmPLkRkUGPAgyB7FTyTqdCeQEEtCbaoEuzh5/JbCKQ6ABhGxwb2fUVGwsYdoiyUXvA2UY85RXffFRYZ3yCpHawQT0gsdLUg1eLmlbJpm6TYKxqQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732095441; c=relaxed/simple; bh=X4fvx7OYW3IFbkZhVwXE01Sd/Yz9bZAt3sV+EvA250I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lfl3ovQGJO0IwzZAdSXwHoJ4uKkCA3vNCwh0UYc4Jos2YmkkkvkRUNJfvdUHNaxBTnT+DynVrbrecE4MHXY3kLZWeXHb/Z4DclaogFjs3UgYti3OyPmYAb/6nCqu+sipYq8xQX76zoXnTPDSbAwgibQ63qN6vO0bgXtgW9MPHxY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=CG44vEbZ; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="CG44vEbZ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=R7oiEFYEVMIo/khuiHsimbHdxohCO0mg/KK57Qh3Fjc=; b=CG44vEbZh5mNOR1judhvLEF8IO ZgJJOJfpVUUSSMmuYuL0lTo/HT25YjiaVzEP5Txt5AdxmhJH7dEb54GCxcOczM3qdQu0YRF1ZzUMk HjM7xxk8Xnj+OmiSZC4+vzZY9j1HcdGNfgdOFCgCuf0ZWG0b1J8lHiVaNdPdiRdFGFzoRAtFCFByz 9LSkzdkhGE8YtsCOEgJt8q/3sRwB+JQbG7LMXvn1enX/7Cc8D4WWYw8C3NAPY9ZEHv2Yd9Sg/SIx7 au+G68Jlf4nmVkyllC48AiRnJKwRRhD5nEs5ECzZZk0OL3KiShyzrY8Seve+8Swa1IZU7p86zE55E yZ7P+8Dw==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tDh9C-0000000Evv9-03kO; Wed, 20 Nov 2024 09:37:18 +0000 Date: Wed, 20 Nov 2024 01:37:17 -0800 From: Christoph Hellwig To: Brian Johannesmeyer Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Raphael Isemann , Cristiano Giuffrida , Herbert Bos , Greg KH , Keith Busch Subject: Re: [RFC v2 1/2] dmapool: Move pool metadata into non-DMA memory Message-ID: References: <20241119205529.3871048-1-bjohannesmeyer@gmail.com> <20241119205529.3871048-2-bjohannesmeyer@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241119205529.3871048-2-bjohannesmeyer@gmail.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Nov 19, 2024 at 09:55:28PM +0100, Brian Johannesmeyer wrote: > + page->blocks_per_page = pool->allocation / pool->size; > + page->blocks = kmalloc_array(page->blocks_per_page, > + sizeof(struct dma_block), GFP_KERNEL); Given that you now need an array of the blocks anyway, it might make sense to switch from a linked list to a bitmap for tracking free state, which would be a lot more efficient as you only need a bit per block as tracking overhead instead of a two pointers and a dma_addr_t. e.g. do a find_first_zero_bit() to find the ffree slot, then calculate the dma_addr and virt address by simple offseting into the dma_page ones with bitnr * pool->size.