From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Date: Fri, 25 Jan 2019 10:50:08 +0000 Subject: Re: [RFC PATCH] x86, numa: always initialize all possible nodes Message-Id: <20190125105008.GJ3560@dhcp22.suse.cz> List-Id: References: <20190114082416.30939-1-mhocko@kernel.org> <20190124141727.GN4087@dhcp22.suse.cz> <3a7a3cf2-b7d9-719e-85b0-352be49a6d0f@intel.com> In-Reply-To: <3a7a3cf2-b7d9-719e-85b0-352be49a6d0f@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dave Hansen Cc: linux-mm@kvack.org, Pingfan Liu , Peter Zijlstra , x86@kernel.org, Benjamin Herrenschmidt , Michael Ellerman , Tony Luck , linuxppc-dev@lists.ozlabs.org, linux-ia64@vger.kernel.org, LKML On Thu 24-01-19 11:10:50, Dave Hansen wrote: > On 1/24/19 6:17 AM, Michal Hocko wrote: > > and nr_cpus set to 4. The underlying reason is tha the device is bound > > to node 2 which doesn't have any memory and init_cpu_to_node only > > initializes memory-less nodes for possible cpus which nr_cpus restrics. > > This in turn means that proper zonelists are not allocated and the page > > allocator blows up. > > This looks OK to me. > > Could we add a few DEBUG_VM checks that *look* for these invalid > zonelists? Or, would our existing list debugging have caught this? Currently we simply blow up because those zonelists are NULL. I do not think we have a way to check whether an existing zonelist is actually _correct_ other thatn check it for NULL. But what would we do in the later case? > Basically, is this bug also a sign that we need better debugging around > this? My earlier patch had a debugging printk to display the zonelists and that might be worthwhile I guess. Basically something like this diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2e097f336126..c30d59f803fb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5259,6 +5259,11 @@ static void build_zonelists(pg_data_t *pgdat) build_zonelists_in_node_order(pgdat, node_order, nr_nodes); build_thisnode_zonelists(pgdat); + + pr_info("node[%d] zonelist: ", pgdat->node_id); + for_each_zone_zonelist(zone, z, &pgdat->node_zonelists[ZONELIST_FALLBACK], MAX_NR_ZONES-1) + pr_cont("%d:%s ", zone_to_nid(zone), zone->name); + pr_cont("\n"); } #ifdef CONFIG_HAVE_MEMORYLESS_NODES -- Michal Hocko SUSE Labs