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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 889A6C3A5A2 for ; Tue, 3 Sep 2019 12:11:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C549208E4 for ; Tue, 3 Sep 2019 12:11:57 +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="btqI5faI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729028AbfICML5 (ORCPT ); Tue, 3 Sep 2019 08:11:57 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:37254 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727077AbfICML4 (ORCPT ); Tue, 3 Sep 2019 08:11:56 -0400 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=8EXrYd4RsH6BhIOlTTrp7nSzyNrjaXwYb7WWqgrRr9Y=; b=btqI5faIUT1LIYYiY9J4zINYa 3jWPSYkalrJbyjVLIJldORJvZuDJ/zHsD1VvNmD4bdXCqkmlPA4w9XGItTEClgoh6M0RckxISoiqc r6niZXlB+7EoS7c6IyPny4ucc7gVTb6eTxrg3fmqRSKg4G66qRDSNmqNUpvZeEfnB4R9iTozEskz7 bbPH5Fa24IlPi9kjfXG3Rie8eQNOoIZB8hkVd/YqYDz9+EBL80/FVfoKcColNHXuUdCBjstZufBB2 hDA2QJyO9yDtah+GC7XcO8XZu47qpuo3x42WciEpEIuFH5lChFZiUVRS6iWB9ohV6ANbP//yvJxUm bozNI4a2g==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1i57f9-0002ll-Km; Tue, 03 Sep 2019 12:11:55 +0000 Date: Tue, 3 Sep 2019 05:11:55 -0700 From: Matthew Wilcox To: Michal Hocko Cc: William Kucharski , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Dave Hansen , Song Liu , Bob Kasten , Mike Kravetz , Chad Mynhier , "Kirill A. Shutemov" , Johannes Weiner Subject: Re: [PATCH v5 1/2] mm: Allow the page cache to allocate large pages Message-ID: <20190903121155.GD29434@bombadil.infradead.org> References: <20190902092341.26712-1-william.kucharski@oracle.com> <20190902092341.26712-2-william.kucharski@oracle.com> <20190903115748.GS14028@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190903115748.GS14028@dhcp22.suse.cz> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Sep 03, 2019 at 01:57:48PM +0200, Michal Hocko wrote: > On Mon 02-09-19 03:23:40, William Kucharski wrote: > > Add an 'order' argument to __page_cache_alloc() and > > do_read_cache_page(). Ensure the allocated pages are compound pages. > > Why do we need to touch all the existing callers and change them to use > order 0 when none is actually converted to a different order? This just > seem to add a lot of code churn without a good reason. If anything I > would simply add __page_cache_alloc_order and make __page_cache_alloc > call it with order 0 argument. Patch 2/2 uses a non-zero order. I agree it's a lot of churn without good reason; that's why I tried to add GFP_ORDER flags a few months ago. Unfortunately, you didn't like that approach either. > Also is it so much to ask callers to provide __GFP_COMP explicitly? Yes, it's an unreasonable burden on the callers. Those that pass 0 will have the test optimised away by the compiler (for the non-NUMA case). For the NUMA case, passing zero is going to be only a couple of extra instructions to not set the GFP_COMP flag. > > #ifdef CONFIG_NUMA > > -extern struct page *__page_cache_alloc(gfp_t gfp); > > +extern struct page *__page_cache_alloc(gfp_t gfp, unsigned int order); > > #else > > -static inline struct page *__page_cache_alloc(gfp_t gfp) > > +static inline struct page *__page_cache_alloc(gfp_t gfp, unsigned int order) > > { > > - return alloc_pages(gfp, 0); > > + if (order > 0) > > + gfp |= __GFP_COMP; > > + return alloc_pages(gfp, order); > > } > > #endif