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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E02ADC433EF for ; Thu, 9 Dec 2021 13:23:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 734816B0071; Thu, 9 Dec 2021 08:23:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6BD706B0073; Thu, 9 Dec 2021 08:23:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5377C6B0074; Thu, 9 Dec 2021 08:23:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id 416956B0071 for ; Thu, 9 Dec 2021 08:23:45 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0B82889B3B for ; Thu, 9 Dec 2021 13:23:35 +0000 (UTC) X-FDA: 78898322790.22.1553D53 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf20.hostedemail.com (Postfix) with ESMTP id B7C5B1C0007 for ; Thu, 9 Dec 2021 13:23:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639056214; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Oed7lLRL08D6q6NEjF2RyvqepJmm1wTl9PlhyX8qLd0=; b=F4vy4xOtlOyEDwezePcah4SgxR5H+hxUPRpiFMuzfuqdZSW8hBrO3T/MyNsKe4fE3hLRdp Q1yc++jEdwOl3kd2ME1E0J47KiR1KZqbaZD3A/ceVXwj5GoR+ya3wiHjayHgpCJZbGwdeG 84rq/RhfKEsjhTQCNi4/ZGd8aeILbnU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-307-Viiw5QZjPaqyCXaTk-Le8A-1; Thu, 09 Dec 2021 08:23:31 -0500 X-MC-Unique: Viiw5QZjPaqyCXaTk-Le8A-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 C3F94801B31; Thu, 9 Dec 2021 13:23:28 +0000 (UTC) Received: from localhost (ovpn-13-171.pek2.redhat.com [10.72.13.171]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 56A7719D9D; Thu, 9 Dec 2021 13:23:17 +0000 (UTC) Date: Thu, 9 Dec 2021 21:23:14 +0800 From: Baoquan He To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, robin.murphy@arm.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, m.szyprowski@samsung.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org Subject: Re: [PATCH RESEND v2 3/5] mm_zone: add function to check if managed dma zone exists Message-ID: <20211209132314.GC3050@MiWiFi-R3L-srv> References: <20211207030750.30824-1-bhe@redhat.com> <20211207030750.30824-4-bhe@redhat.com> <0a9bc228-21ba-abe3-d9c8-b9d52b936366@redhat.com> <20211209130210.GB3050@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: B7C5B1C0007 X-Stat-Signature: r6wft4gt5khthmy4nt4zdnbr5bcsydeg Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=F4vy4xOt; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf20.hostedemail.com: domain of bhe@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=bhe@redhat.com X-HE-Tag: 1639056214-189131 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 12/09/21 at 02:10pm, David Hildenbrand wrote: ...... > >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>> index c5952749ad40..ac0ea42a4e5f 100644 > >>> --- a/mm/page_alloc.c > >>> +++ b/mm/page_alloc.c > >>> @@ -9459,4 +9459,15 @@ bool take_page_off_buddy(struct page *page) > >>> spin_unlock_irqrestore(&zone->lock, flags); > >>> return ret; > >>> } > >>> + > >>> +bool has_managed_dma(void) > >>> +{ > >>> + struct zone *zone; > >>> + > >>> + for_each_managed_zone(zone) { > >>> + if (zone_is_dma(zone)) > >>> + return true; > >>> + } > >>> + return false; > >>> +} > >> > >> Wouldn't it be "easier/faster" to just iterate online nodes and directly > >> obtain the ZONE_DMA, checking if there are managed pages? > > > > Thanks, Dave. > > > > Please check for_each_managed_zone(), it is iterating online nodes and > > it's each managed zone. > > > > Is below what you are suggesting? The only difference is I introduced > > for_each_managed_zone() which can be reused later if needed. Not sure if > > I got your suggestion correctly. > > > > bool has_managed_dma(void) > > { > > struct pglist_data *pgdat; > > struct zone *zone; > > enum zone_type i, j; > > > > for_each_online_pgdat(pgdat) { > > for (i = 0; i < MAX_NR_ZONES - 1; i++) { > > struct zone *zone = &pgdat->node_zones[i]; > > if (zone_is_dma(zone)) > > return true; > > } > > } > > return false; > > > > } > > > Even simpler, no need to iterate over zones at all, only over nodes: > > #ifdef CONFIG_ZONE_DMA > bool has_managed_dma(void) > { > struct pglist_data *pgdat; > > for_each_online_pgdat(pgdat) { > struct zone *zone = &pgdat->node_zones[ZONE_DMA]; > > if (managed_zone(zone) > return true; > } > return false; > } > #endif /* CONFIG_ZONE_DMA */ > > Without CONFIG_ZONE_DMA, simply provide a dummy in the header that > returns false. Yeah, it only iterates the number of nodes times. I will take this in v3. Thanks, David.