From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mvJOZ-00G5hB-6y for kexec@lists.infradead.org; Thu, 09 Dec 2021 13:23:36 +0000 Date: Thu, 9 Dec 2021 21:23:14 +0800 From: Baoquan He 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-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org 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 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. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec