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 77C8EC3A5A2 for ; Tue, 3 Sep 2019 16:28:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3C32623789 for ; Tue, 3 Sep 2019 16:28:40 +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="oCJ92zCv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3C32623789 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CD1626B0003; Tue, 3 Sep 2019 12:28:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C81D26B0005; Tue, 3 Sep 2019 12:28:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B71466B0006; Tue, 3 Sep 2019 12:28:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0130.hostedemail.com [216.40.44.130]) by kanga.kvack.org (Postfix) with ESMTP id 932CA6B0003 for ; Tue, 3 Sep 2019 12:28:39 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 00167180AD801 for ; Tue, 3 Sep 2019 16:28:38 +0000 (UTC) X-FDA: 75894142758.03.burn17_1140517f73d46 X-HE-Tag: burn17_1140517f73d46 X-Filterd-Recvd-Size: 4151 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Tue, 3 Sep 2019 16:28:38 +0000 (UTC) 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=A01EoZVAbENBU2ODnei5aZC/eSyCxIe7RviRDSpgglA=; b=oCJ92zCv0vaLqsiIF+BEQ5E5E 8tWg574OR1tXDNAdgxaEW9ZOtC9RgXU1YeUw55xOc80zTVRnxZCyUCNLfBkNAZiwoSCt+KyE7f7Kk ECF8MrNiznXkAufY1RvmwEc4odtOEh9+oHbf3hsI4VKg4VwUYZq5xwAupL2R1uln6DSGhJXwYQuI8 RZQyCR8PGBPL7nxrArCSdqjcBVWN6LLgHZFUTqJMg7UzRJqLSd6mxYw8FwJFmVgpPJ2xIqwp5z5fm /eE8MkNJ96Iu/HNE71eque6R66Ku7pz2Xo1iouPfCUsPb8CZ13tGOYrgSNMyfPJp/XL4BMK5TpA+i lQqXK0fyg==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1i5BfT-000149-Ek; Tue, 03 Sep 2019 16:28:31 +0000 Date: Tue, 3 Sep 2019 09:28:31 -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: <20190903162831.GI29434@bombadil.infradead.org> References: <20190902092341.26712-1-william.kucharski@oracle.com> <20190902092341.26712-2-william.kucharski@oracle.com> <20190903115748.GS14028@dhcp22.suse.cz> <20190903121155.GD29434@bombadil.infradead.org> <20190903121952.GU14028@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190903121952.GU14028@dhcp22.suse.cz> User-Agent: Mutt/1.11.4 (2019-03-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Sep 03, 2019 at 02:19:52PM +0200, Michal Hocko wrote: > On Tue 03-09-19 05:11:55, Matthew Wilcox wrote: > > 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. > > It is a new caller and it can use a new function right? > > > 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. > > Is there any future plan that all/most __page_cache_alloc will get a > non-zero order argument? I'm not sure about "most". It will certainly become more common, as far as I can tell. > > > Also is it so much to ask callers to provide __GFP_COMP explicitly? > > > > Yes, it's an unreasonable burden on the callers. > > Care to exaplain why? __GFP_COMP tends to be used in the kernel quite > extensively. Most of the places which call this function get their gfp_t from mapping->gfp_mask. If we only want to allocate a single page, we must not set __GFP_COMP. If we want to allocate a large page, we must set __GFP_COMP. Rather than require individual filesystems to concern themselves with this wart of the GFP interface, we can solve it in the page cache.