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 X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BE5CC3B186 for ; Wed, 12 Feb 2020 08:13:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 470CE2073C for ; Wed, 12 Feb 2020 08:13:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Xg4US8EA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728465AbgBLINl (ORCPT ); Wed, 12 Feb 2020 03:13:41 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:34404 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728287AbgBLINk (ORCPT ); Wed, 12 Feb 2020 03:13:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; 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=xZfWd1AJTNbOk+bHxFddhCEkeI06/CUELyUjy4uk11c=; b=Xg4US8EARSSirwDPiLRmi6pFg8 Y8KP6yaDbZBjT/yx0qcM6BGzgIX4PwGmHse6ymcZeKuh56v8RoWo1DQliTHeYqMmnApT9ThTOjoJZ IVsIQwA6lBduQfWD0CmtX0lE1Meq+/VfJl7fq7ItZYhjJQlikAFej3HwC3Lx3+k2F4lX551cxIl46 uNP0KBdRrrUHUFpormJ+sYXenWUTcaiqvn0HdIlqxkb3dWvuwcYKsFQA9hsPGa6/K4mg2X8ZCggN0 Dk6nf6clFcmqH/JVTYE9vUqh3K5DyQYtsqqKVyWV8Q/+Hkd+BE+TxqVnm1SMswtJdRjVHa0VXMzUV gMMlu0MQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1n9Q-0005DC-8F; Wed, 12 Feb 2020 08:13:40 +0000 Date: Wed, 12 Feb 2020 00:13:40 -0800 From: Christoph Hellwig To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 16/25] iomap: Support large pages in read paths Message-ID: <20200212081340.GD24497@infradead.org> References: <20200212041845.25879-1-willy@infradead.org> <20200212041845.25879-17-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200212041845.25879-17-willy@infradead.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org > +/* > + * Estimate the number of vectors we need based on the current page size; > + * if we're wrong we'll end up doing an overly large allocation or needing > + * to do a second allocation, neither of which is a big deal. > + */ > +static unsigned int iomap_nr_vecs(struct page *page, loff_t length) > +{ > + return (length + thp_size(page) - 1) >> page_shift(page); > +} With the multipage bvecs a huge page (or any physically contigous piece of memory) will always use one or less (if merged into the previous) bio_vec. So this can be simplified and optimized.