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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84C05C04A6A for ; Tue, 15 Aug 2023 17:07:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238620AbjHORHK (ORCPT ); Tue, 15 Aug 2023 13:07:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238625AbjHORGm (ORCPT ); Tue, 15 Aug 2023 13:06:42 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34DC51990 for ; Tue, 15 Aug 2023 10:06:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=vZqPRg3r0m5C1a2IsUiQeDDBtBFofgrb7BHNPuc4+8E=; b=ay03J/B2Fx0p2iGHY4Nyfg/Hor wUdxyG7UOgsk+vljXcadenka3BHlsnb604xTvvd6KRflAKI9gSLVa8PsnsnN6s93eFiOMXSGLrZrw 40yCOprE0w7Yuqsfz4AFsPpFgELv/GyTPDERzv/ZmCE8B4oRyb4m/9vYsoXiEVbKRvWExkfyIKUnT jzrRIyQc5IyBfVrmws2/TdMLcqJys9tfXhPrqIloqHiHfDg5iKJcqDnBia/FzxulTDKEVkaT6oFwR hIKccArwWkdefAJN6FzWXCZz32ll1MMwxR8OxprNfb4sZNOTZTlvoHMdnYjRodPcd1+2Tzpu1PMIY z9lNvBHw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qVxV5-009O6Q-Sn; Tue, 15 Aug 2023 17:06:35 +0000 Date: Tue, 15 Aug 2023 18:06:35 +0100 From: Matthew Wilcox To: David Hildenbrand Cc: Andrew Morton , Jens Axboe , io-uring@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 7/9] mm: Add deferred_list page flag Message-ID: References: <20230815032645.1393700-1-willy@infradead.org> <20230815032645.1393700-8-willy@infradead.org> <7c1bb01d-620c-ca97-c4a2-2bb7c126c687@redhat.com> <88bdc3d2-56e4-4c09-77fe-74fb4c116893@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <88bdc3d2-56e4-4c09-77fe-74fb4c116893@redhat.com> Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Tue, Aug 15, 2023 at 06:40:55PM +0200, David Hildenbrand wrote: > On 15.08.23 17:32, Matthew Wilcox wrote: > > On Tue, Aug 15, 2023 at 09:54:36AM +0200, David Hildenbrand wrote: > > > On 15.08.23 05:26, Matthew Wilcox (Oracle) wrote: > > > > Stored in the first tail page's flags, this flag replaces the destructor. > > > > That removes the last of the destructors, so remove all references to > > > > folio_dtor and compound_dtor. > > > > > > > > Signed-off-by: Matthew Wilcox (Oracle) > > > > --- > > > > > > [...] > > > > > > > + /* Has a deferred list (may be empty). First tail page. */ > > > > + PG_deferred_list = PG_reclaim, > > > > + > > > > > > If PG_deferred_list implies thp (and replaces the thp dtor), should we > > > rather name this PG_thp or something along those lines? > > > > We're trying to use 'thp' to mean 'a folio which is pmd mappable', > > so I'd rather not call it that. > > There is no conclusion on that. Theree are a lot of counters called THP and TransHuge and other variants which are exposed to userspace, and the (user) assumption is that this counts PMD-sized folios. If you grep around for folio_test_pmd_mappable(), you'll find them. If we have folio_test_thp(), people will write: if (folio_test_thp(folio)) __mod_lruvec_state(lruvec, NR_SHMEM_THPS, nr); instead of using folio_test_pmd_mappable(). > After all, the deferred split queue is just an implementation detail, and it > happens to live in tailpage 2, no? > > Once we would end up initializing something else in prep_transhuge_page(), > it would turn out pretty confusing if that is called folio_remove_deferred() > ... Perhaps the key difference between normal compound pages and file/anon compound pages is that the latter are splittable? So we can name all of this: folio_init_splittable() folio_test_splittable() folio_fini_splittable() Maybe that's still too close to an implementation detail, but it's at least talking about _a_ characteristic of the folio, even if it's not the _only_ characteristic of the folio.