| 
 Hi Steve, 
  
I think this has nothing directly to do with xen, it's more a sort of 
out of kernel memory in linux. 
See below. 
  
Am 25.10.2011 schrieb "Steve Allison <xen-users@xxxxxxxxxxxxxxxxxx>": 
> Dear list, 
>  
> I am seeing an error across multiple machines during heavy I/O, either  
> disk or network. The VMs are on different Intel CPUs (Core 2 Quad, Core  
> i5, Xeon) with varying boards (Abit, Asus, Supermicro). 
>  
> Machines that get this error are running either BackupPC, Zabbix (MySQL)  
> or SABNZBd. I can also reproduce the error on the Supermicros with a  
> looped wget of an ubuntu ISO as they are on Gbit ethernet and will  
> download at ~70MB/s. 
>  
> I prefer Debian, however whilst troubleshooting I have used SUSE kernel  
> with Debian and CentOS. I have compiled kernels from 2.6.3x to 3.0.x and  
> Xen 4.0.1 to 4.1, and have yet to shake the issue. 
>  
> The following is an output of the error. This is usually repeated  
> several times. There is plenty of RAM available, usually 1GB+ is used in  
> buffers/cache, but ~1GB of swap is also available should it be needed. 
>  
> Its worth noting that the "swapper" portion is usually a random process.  
> I've seen it say "mingetty", "rsyslog" amongst others. However "swapper"  
> is the most common. 
>  
> [488054.896037] swapper: page allocation failure. order:0, mode:0x20 
  
The message above comes from the linux kernel function __alloc_pages_nodemask() 
which means, no free memory and then dump_stack() is called - see below. 
  
> [488054.896056] Pid: 0, comm: swapper Not tainted 2.6.32-5-amd64 #1 
> [488054.896067] Call Trace: 
> [488054.896074]<IRQ>   [<ffffffff810ba5d6>] ? __alloc_pages_nodemask+0x592/0x5f4 
> [488054.896100]  [<ffffffff810e6912>] ? new_slab+0x5b/0x1ca 
> [488054.896112]  [<ffffffff810e6c71>] ? __slab_alloc+0x1f0/0x39b 
> [488054.896124]  [<ffffffff8124851e>] ? __alloc_skb+0x3e/0x15a 
> [488054.896135]  [<ffffffff8124851e>] ? __alloc_skb+0x3e/0x15a 
> [488054.896146]  [<ffffffff810e704d>] ? kmem_cache_alloc_node+0x8b/0x10b 
> [488054.896158]  [<ffffffff8124851e>] ? __alloc_skb+0x3e/0x15a 
> [488054.896170]  [<ffffffff8128b0e7>] ? tcp_delack_timer+0x0/0x1fe 
> [488054.896182]  [<ffffffff812880fd>] ? tcp_send_ack+0x23/0xf4 
> [488054.896193]  [<ffffffff8128b275>] ? tcp_delack_timer+0x18e/0x1fe 
> [488054.896207]  [<ffffffff8105a5ff>] ? run_timer_softirq+0x1c9/0x268 
> [488054.896220]  [<ffffffff81094a9f>] ? handle_IRQ_event+0x117/0x126 
> [488054.896234]  [<ffffffff81053cab>] ? __do_softirq+0xdd/0x1a6 
> [488054.896245]  [<ffffffff81096154>] ? handle_percpu_irq+0x4e/0x6a 
> [488054.896258]  [<ffffffff81011cac>] ? call_softirq+0x1c/0x30 
> [488054.896269]  [<ffffffff8101322b>] ? do_softirq+0x3f/0x7c 
> [488054.896280]  [<ffffffff81053b1b>] ? irq_exit+0x36/0x76 
  
Xen is only involved as an interrupt is delivered from hypervisor to the linux 
kernel. 
  
> [488054.896291]  [<ffffffff811ef48c>] ? xen_evtchn_do_upcall+0x33/0x41 
> [488054.896304]  [<ffffffff81011cfe>] ? xen_do_hypervisor_callback+0x1e/0x30 
> [488054.896313]<EOI>   [<ffffffff810093aa>] ? hypercall_page+0x3aa/0x1001 
> [488054.896330]  [<ffffffff810093aa>] ? hypercall_page+0x3aa/0x1001 
> [488054.896343]  [<ffffffff8100e160>] ? xen_vcpuop_set_next_event+0x0/0x60 
> [488054.896354]  [<ffffffff8100dcb3>] ? xen_safe_halt+0xc/0x15 
> [488054.896366]  [<ffffffff8100be63>] ? xen_idle+0x37/0x40 
> [488054.896377]  [<ffffffff8100feb1>] ? cpu_idle+0xa2/0xda 
> [488054.896388]  [<ffffffff814f5cdd>] ? start_kernel+0x3dc/0x3e8 
> [488054.896397] Mem-Info: 
> [488054.896404] Node 0 DMA per-cpu: 
> [488054.896413] CPU    0: hi:    0, btch:   1 usd:   0 
> [488054.896422] CPU    1: hi:    0, btch:   1 usd:   0 
> [488054.896431] CPU    2: hi:    0, btch:   1 usd:   0 
> [488054.896439] CPU    3: hi:    0, btch:   1 usd:   0 
> [488054.896447] Node 0 DMA32 per-cpu: 
> [488054.896456] CPU    0: hi:  186, btch:  31 usd: 185 
> [488054.896465] CPU    1: hi:  186, btch:  31 usd: 172 
> [488054.896473] CPU    2: hi:  186, btch:  31 usd: 166 
> [488054.896482] CPU    3: hi:  186, btch:  31 usd: 148 
> [488054.896494] active_anon:89704 inactive_anon:31826 isolated_anon:0 
> [488054.896497]  active_file:27715 inactive_file:277856 isolated_file:0 
> [488054.896499]  unevictable:0 dirty:30010 writeback:0 unstable:0 
> [488054.896501]  free:2220 slab_reclaimable:11510 slab_unreclaimable:1813 
> [488054.896503]  mapped:2981 shmem:102 pagetables:1274 bounce:0 
> [488054.896532] Node 0 DMA free:6996kB min:36kB low:44kB high:52kB active_anon:0kB inactive_anon:152kB active_file:56kB inactive_file:5148kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:12304kB mlocked:0kB dirty:0kB writeback:0kB mapped:32kB shmem:0kB slab_reclaimable:100kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no 
> [488054.896575] lowmem_reserve[]: 0 1751 1751 1751 
> [488054.896593] Node 0 DMA32 free:1884kB min:5332kB low:6664kB high:7996kB active_anon:358816kB inactive_anon:127152kB active_file:110804kB inactive_file:1106276kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:1793760kB mlocked:0kB dirty:120040kB writeback:0kB mapped:11892kB shmem:408kB slab_reclaimable:45940kB slab_unreclaimable:7252kB kernel_stack:1176kB pagetables:5096kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no 
> [488054.896639] lowmem_reserve[]: 0 0 0 0 
> [488054.896656] Node 0 DMA: 3*4kB 1*8kB 2*16kB 1*32kB 4*64kB 2*128kB 3*256kB 3*512kB 2*1024kB 1*2048kB 0*4096kB = 6996kB 
> [488054.896695] Node 0 DMA32: 19*4kB 2*8kB 0*16kB 0*32kB 0*64kB 4*128kB 1*256kB 0*512kB 1*1024kB 0*2048kB 0*4096kB = 1884kB 
> [488054.896733] 306011 total pagecache pages 
> [488054.896741] 338 pages in swap cache 
> [488054.896748] Swap cache stats: add 1457, delete 1119, find 106250/106300 
> [488054.896757] Free swap  = 1044524kB 
> [488054.896764] Total swap = 1048568kB 
> [488054.900014] 458752 pages RAM 
> [488054.900014] 9907 pages reserved 
> [488054.900014] 303804 pages shared 
> [488054.900014] 151251 pages non-shared 
> [488054.900014] SLUB: Unable to allocate memory on node -1 (gfp=0x20) 
> [488054.900014]   cache: kmalloc-256, object size: 256, buffer size: 256, default order: 0, min order: 0 
> [488054.900014]   node 0: slabs: 62, objs: 992, free: 0 
>  
> 
> Any guidance much appreciated. 
  
Maybe you must give more memory to the linux system but I'am not real sure, 
beeing not an expert there. 
Dietmar. 
  
>  
> Regards, 
> Steve. 
>  
>  
 
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