From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nishanth Aravamudan Date: Mon, 21 Jul 2014 17:47:54 +0000 Subject: Re: [RFC Patch V1 28/30] mm: Update _mem_id_[] for every possible CPU when memory configuration chan Message-Id: <20140721174754.GE4156@linux.vnet.ibm.com> List-Id: References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com> <1405064267-11678-29-git-send-email-jiang.liu@linux.intel.com> In-Reply-To: <1405064267-11678-29-git-send-email-jiang.liu@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jiang Liu Cc: Andrew Morton , Mel Gorman , David Rientjes , Mike Galbraith , Peter Zijlstra , "Rafael J . Wysocki" , Rik van Riel , Johannes Weiner , "Srivatsa S. Bhat" , Dave Hansen , Tony Luck , linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org On 11.07.2014 [15:37:45 +0800], Jiang Liu wrote: > Current kernel only updates _mem_id_[cpu] for onlined CPUs when memory > configuration changes. So kernel may allocate memory from remote node > for a CPU if the CPU is still in absent or offline state even if the > node associated with the CPU has already been onlined. This just sounds like the topology information is being updated at the wrong place/time? That is, the memory is online, the CPU is being brought online, but isn't associated with any node? > This patch tries to improve performance by updating _mem_id_[cpu] for > each possible CPU when memory configuration changes, thus kernel could > always allocate from local node once the node is onlined. Ok, what is the impact? Do you actually see better performance? > We check node_online(cpu_to_node(cpu)) because: > 1) local_memory_node(nid) needs to access NODE_DATA(nid) > 2) try_offline_node(nid) just zeroes out NODE_DATA(nid) instead of free it > > Signed-off-by: Jiang Liu > --- > mm/page_alloc.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0ea758b898fd..de86e941ed57 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3844,13 +3844,13 @@ static int __build_all_zonelists(void *data) > /* > * We now know the "local memory node" for each node-- > * i.e., the node of the first zone in the generic zonelist. > - * Set up numa_mem percpu variable for on-line cpus. During > - * boot, only the boot cpu should be on-line; we'll init the > - * secondary cpus' numa_mem as they come on-line. During > - * node/memory hotplug, we'll fixup all on-line cpus. > + * Set up numa_mem percpu variable for all possible cpus > + * if associated node has been onlined. > */ > - if (cpu_online(cpu)) > + if (node_online(cpu_to_node(cpu))) > set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu))); > + else > + set_cpu_numa_mem(cpu, NUMA_NO_NODE); > #endif