From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wanpeng Li Subject: Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory Date: Tue, 7 Jan 2014 17:49:44 +0800 Message-ID: <43341.3972649307$1389088226@news.gmane.org> References: <20140107132100.5b5ad198@kryten> <20140107074136.GA4011@lge.com> <52cbbf7b.2792420a.571c.ffffd476SMTPIN_ADDED_BROKEN@mx.google.com> <20140107091016.GA21965@lge.com> <52cbc738.c727440a.5ead.27a3SMTPIN_ADDED_BROKEN@mx.google.com> <20140107093156.GA10157@lge.com> Reply-To: Wanpeng Li Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20140107093156.GA10157@lge.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Sender: "Linuxppc-dev" To: Joonsoo Kim Cc: cl@linux-foundation.org, nacc@linux.vnet.ibm.com, penberg@kernel.org, linux-mm@kvack.org, paulus@samba.org, Anton Blanchard , mpm@selenic.com, linuxppc-dev@lists.ozlabs.org List-Id: linux-mm.kvack.org On Tue, Jan 07, 2014 at 06:31:56PM +0900, Joonsoo Kim wrote: >On Tue, Jan 07, 2014 at 05:21:45PM +0800, Wanpeng Li wrote: >> On Tue, Jan 07, 2014 at 06:10:16PM +0900, Joonsoo Kim wrote: >> >On Tue, Jan 07, 2014 at 04:48:40PM +0800, Wanpeng Li wrote: >> >> Hi Joonsoo, >> >> On Tue, Jan 07, 2014 at 04:41:36PM +0900, Joonsoo Kim wrote: >> >> >On Tue, Jan 07, 2014 at 01:21:00PM +1100, Anton Blanchard wrote: >> >> >> >> >> [...] >> >> >Hello, >> >> > >> >> >I think that we need more efforts to solve unbalanced node problem. >> >> > >> >> >With this patch, even if node of current cpu slab is not favorable to >> >> >unbalanced node, allocation would proceed and we would get the unintended memory. >> >> > >> >> >> >> We have a machine: >> >> >> >> [ 0.000000] Node 0 Memory: >> >> [ 0.000000] Node 4 Memory: 0x0-0x10000000 0x20000000-0x60000000 0x80000000-0xc0000000 >> >> [ 0.000000] Node 6 Memory: 0x10000000-0x20000000 0x60000000-0x80000000 >> >> [ 0.000000] Node 10 Memory: 0xc0000000-0x180000000 >> >> >> >> [ 0.041486] Node 0 CPUs: 0-19 >> >> [ 0.041490] Node 4 CPUs: >> >> [ 0.041492] Node 6 CPUs: >> >> [ 0.041495] Node 10 CPUs: >> >> >> >> The pages of current cpu slab should be allocated from fallback zones/nodes >> >> of the memoryless node in buddy system, how can not favorable happen? >> > >> >Hi, Wanpeng. >> > >> >IIRC, if we call kmem_cache_alloc_node() with certain node #, we try to >> >allocate the page in fallback zones/node of that node #. So fallback list isn't >> >related to fallback one of memoryless node #. Am I wrong? >> > >> >> Anton add node_spanned_pages(node) check, so current cpu slab mentioned >> above is against memoryless node. If I miss something? > >I thought following scenario. > >memoryless node # : 1 >1's fallback node # : 0 > >On node 1's cpu, > >1. kmem_cache_alloc_node (node 2) >2. allocate the page on node 2 for the slab, now cpu slab is that one. >3. kmem_cache_alloc_node (local node, that is, node 1) >4. It check node_spanned_pages() and find it is memoryless node. >So return node 2's memory. > >Is it impossible scenario? > Indeed, it can happen. Regards, Wanpeng Li >Thanks.