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=-9.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 156CEC4727E for ; Mon, 5 Oct 2020 12:16:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9891420848 for ; Mon, 5 Oct 2020 12:16:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="F3Hu6yhj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9891420848 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1E6D46B006C; Mon, 5 Oct 2020 08:16:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1BBDC6B006E; Mon, 5 Oct 2020 08:16:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0838E6B0070; Mon, 5 Oct 2020 08:16:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0128.hostedemail.com [216.40.44.128]) by kanga.kvack.org (Postfix) with ESMTP id D1D8E6B006C for ; Mon, 5 Oct 2020 08:16:19 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 4F87F3630 for ; Mon, 5 Oct 2020 12:16:19 +0000 (UTC) X-FDA: 77337769278.09.point09_320691b271be Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id 3CEFE180AD806 for ; Mon, 5 Oct 2020 12:16:19 +0000 (UTC) X-HE-Tag: point09_320691b271be X-Filterd-Recvd-Size: 7162 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Mon, 5 Oct 2020 12:16:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601900178; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tgT/XV/JOTuCj2JcNLuFxyO0AHRuTyQafR/eZPht6eo=; b=F3Hu6yhjDsLWnnwHCJ2NzgvE2CFAyt33eJNqrJU5HEWiymxeO7xb6BZ2bzpmKuJJg8Bzs9 HaOCKLwVRw6hVJmNSBrnJfiUG4QCoSx95OrG7tNU6oi7Hy+I6nJ81skhlS2naAfxS0yTt5 Zs1NtOEw3WpD/RlpKGI8pAL1qHpSTFE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-416-a6njIh0COVKiFYMipVIPug-1; Mon, 05 Oct 2020 08:16:16 -0400 X-MC-Unique: a6njIh0COVKiFYMipVIPug-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 13F738030AA; Mon, 5 Oct 2020 12:16:13 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-222.ams2.redhat.com [10.36.114.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id B73DF27CC6; Mon, 5 Oct 2020 12:15:59 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, linux-acpi@vger.kernel.org, Andrew Morton , Matthew Wilcox , David Hildenbrand , Alexander Duyck , Oscar Salvador , Wei Yang , Pankaj Gupta , Michal Hocko , Mel Gorman , Michal Hocko , Dave Hansen , Vlastimil Babka , Mike Rapoport , Scott Cheloha , Michael Ellerman Subject: [PATCH v2 2/5] mm/page_alloc: place pages to tail in __putback_isolated_page() Date: Mon, 5 Oct 2020 14:15:31 +0200 Message-Id: <20201005121534.15649-3-david@redhat.com> In-Reply-To: <20201005121534.15649-1-david@redhat.com> References: <20201005121534.15649-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Content-Transfer-Encoding: quoted-printable 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: __putback_isolated_page() already documents that pages will be placed to the tail of the freelist - this is, however, not the case for "order >=3D MAX_ORDER - 2" (see buddy_merge_likely()) - which should be the case for all existing users. This change affects two users: - free page reporting - page isolation, when undoing the isolation (including memory onlining). This behavior is desireable for pages that haven't really been touched lately, so exactly the two users that don't actually read/write page content, but rather move untouched pages. The new behavior is especially desirable for memory onlining, where we allow allocation of newly onlined pages via undo_isolate_page_range() in online_pages(). Right now, we always place them to the head of the freelist, resulting in undesireable behavior: Assume we add individual memory chunks via add_memory() and online them right away to the NORMAL zone. We create a dependency chain of unmovable allocations e.g., via the memmap. The memmap of the next chunk will be placed onto previous chunks - if the last block cannot get offlined+removed, all dependent ones cannot get offlined+removed. While this can already be observed with individual DIMMs, it's more of an issue for virtio-mem (and I suspect also ppc DLPAR). Document that this should only be used for optimizations, and no code should rely on this behavior for correction (if the order of the freelists ever changes). We won't care about page shuffling: memory onlining already properly shuffles after onlining. free page reporting doesn't care about physically contiguous ranges, and there are already cases where page isolation will simply move (physically close) free pages to (currently) the head of the freelists via move_freepages_block() instead of shuffling. If this becomes ever relevant, we should shuffle the whole zone when undoing isolation of larger ranges, and after free_contig_range(). Reviewed-by: Alexander Duyck Reviewed-by: Oscar Salvador Reviewed-by: Wei Yang Reviewed-by: Pankaj Gupta Acked-by: Michal Hocko Cc: Andrew Morton Cc: Alexander Duyck Cc: Mel Gorman Cc: Michal Hocko Cc: Dave Hansen Cc: Vlastimil Babka Cc: Wei Yang Cc: Oscar Salvador Cc: Mike Rapoport Cc: Scott Cheloha Cc: Michael Ellerman Signed-off-by: David Hildenbrand --- mm/page_alloc.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2bf235b1953f..df5ff0cd6df1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -94,6 +94,18 @@ typedef int __bitwise fpi_t; */ #define FPI_SKIP_REPORT_NOTIFY ((__force fpi_t)BIT(0)) =20 +/* + * Place the (possibly merged) page to the tail of the freelist. Will ig= nore + * page shuffling (relevant code - e.g., memory onlining - is expected t= o + * shuffle the whole zone). + * + * Note: No code should rely on this flag for correctness - it's purely + * to allow for optimizations when handing back either fresh pages + * (memory onlining) or untouched pages (page isolation, free page + * reporting). + */ +#define FPI_TO_TAIL ((__force fpi_t)BIT(1)) + /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields= */ static DEFINE_MUTEX(pcp_batch_high_lock); #define MIN_PERCPU_PAGELIST_FRACTION (8) @@ -1044,7 +1056,9 @@ static inline void __free_one_page(struct page *pag= e, done_merging: set_page_order(page, order); =20 - if (is_shuffle_order(order)) + if (fpi_flags & FPI_TO_TAIL) + to_tail =3D true; + else if (is_shuffle_order(order)) to_tail =3D shuffle_pick_tail(); else to_tail =3D buddy_merge_likely(pfn, buddy_pfn, page, order); @@ -3306,7 +3320,7 @@ void __putback_isolated_page(struct page *page, uns= igned int order, int mt) =20 /* Return isolated page to tail of freelist. */ __free_one_page(page, page_to_pfn(page), zone, order, mt, - FPI_SKIP_REPORT_NOTIFY); + FPI_SKIP_REPORT_NOTIFY | FPI_TO_TAIL); } =20 /* --=20 2.26.2