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=-6.8 required=3.0 tests=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 639FFC3A59F for ; Thu, 29 Aug 2019 07:00:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 44F0F233A1 for ; Thu, 29 Aug 2019 07:00:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727935AbfH2HAx (ORCPT ); Thu, 29 Aug 2019 03:00:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57376 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbfH2HAv (ORCPT ); Thu, 29 Aug 2019 03:00:51 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 871E43B738; Thu, 29 Aug 2019 07:00:51 +0000 (UTC) Received: from t460s.redhat.com (ovpn-117-166.ams2.redhat.com [10.36.117.166]) by smtp.corp.redhat.com (Postfix) with ESMTP id B0D861001B07; Thu, 29 Aug 2019 07:00:49 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Oscar Salvador , Michal Hocko , Pavel Tatashin , Dan Williams , Wei Yang Subject: [PATCH v3 05/11] mm/memory_hotplug: Optimize zone shrinking code when checking for holes Date: Thu, 29 Aug 2019 09:00:13 +0200 Message-Id: <20190829070019.12714-6-david@redhat.com> In-Reply-To: <20190829070019.12714-1-david@redhat.com> References: <20190829070019.12714-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 29 Aug 2019 07:00:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ... and clarify why this is needed at all right now. It all boils down to false positives. We will try to remove the false positives for !ZONE_DEVICE memory, soon, however, for ZONE_DEVICE memory we won't be able to easily get rid of false positives. Don't only detect "all holes" but try to shrink using the existing functions we have. Cc: Andrew Morton Cc: Oscar Salvador Cc: David Hildenbrand Cc: Michal Hocko Cc: Pavel Tatashin Cc: Dan Williams Cc: Wei Yang Signed-off-by: David Hildenbrand --- mm/memory_hotplug.c | 45 +++++++++++++++++++++++---------------------- 1 file changed, 23 insertions(+), 22 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index d3c34bbeb36d..663853bf97ed 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -411,32 +411,33 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, } } - /* - * The section is not biggest or smallest mem_section in the zone, it - * only creates a hole in the zone. So in this case, we need not - * change the zone. But perhaps, the zone has only hole data. Thus - * it check the zone has only hole or not. - */ - for (pfn = zone->zone_start_pfn; - pfn < zone_end_pfn(zone); pfn += PAGES_PER_SUBSECTION) { - if (unlikely(!pfn_valid(pfn))) - continue; - - if (page_zone(pfn_to_page(pfn)) != zone) - continue; - - /* Skip range to be removed */ - if (pfn >= start_pfn && pfn < end_pfn) - continue; - - /* If we find valid section, we have nothing to do */ + if (!zone->spanned_pages) { zone_span_writeunlock(zone); return; } - /* The zone has no valid section */ - zone->zone_start_pfn = 0; - zone->spanned_pages = 0; + /* + * Due to false positives in previous skrink attempts, it can happen + * that we can shrink the zones further (possibly to zero). Once we + * can reliably detect which PFNs actually belong to a zone + * (especially for ZONE_DEVICE memory where we don't have online + * sections), this can go. + */ + pfn = find_smallest_section_pfn(nid, zone, zone->zone_start_pfn, + zone_end_pfn(zone)); + if (pfn) { + zone->spanned_pages = zone_end_pfn(zone) - pfn; + zone->zone_start_pfn = pfn; + + pfn = find_biggest_section_pfn(nid, zone, zone->zone_start_pfn, + zone_end_pfn(zone)); + if (pfn) + zone->spanned_pages = pfn - zone->zone_start_pfn + 1; + } + if (!pfn) { + zone->zone_start_pfn = 0; + zone->spanned_pages = 0; + } zone_span_writeunlock(zone); } -- 2.21.0