* Srikar Dronamraju [off-list ref] [2012-12-10 10:37:10]:

quoted

Either way, last night I applied a patch on top of latest tip/master to
remove the nr_cpus_allowed check so that numacore would be enabled again
and tested that. In some places it has indeed much improved. In others
it is still regressing badly and in two case, it's corrupting memory --
specjbb when THP is enabled crashes when running for single or multiple
JVMs. It is likely that a zero page is being inserted due to a race with
migration and causes the JVM to throw a null pointer exception. Here is
the comparison on the rough off-chance you actually read it this time.

I see this failure when running with THP and KSM enabled on 
Friday's Tip master. Not sure if Mel was talking about the same issue.

 
Even occurs with !THP but KSM enabled.

------------[ cut here ]------------
kernel BUG at ../kernel/sched/fair.c:2371!
invalid opcode: 0000 [#1] SMP
Modules linked in: ebtable_nat ebtables autofs4 sunrpc cpufreq_ondemand acpi_cpufreq freq_table mperf bridge stp llc iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 vhost_net macvtap macvlan tun iTCO_wdt iTCO_vendor_support kvm_intel kvm microcode cdc_ether usbnet mii serio_raw i2c_i801 i2c_core lpc_ich mfd_core shpchp ioatdma i7core_edac edac_core bnx2 sg ixgbe dca mdio ext4 mbcache jbd2 sd_mod crc_t10dif mptsas mptscsih mptbase scsi_transport_sas dm_mirror dm_region_hash dm_log dm_mod
CPU 4
Pid: 116, comm: ksmd Not tainted 3.7.0-rc8-tip_master+ #5 IBM BladeCenter HS22V -[7871AC1]-/81Y5995
RIP: 0010:[<ffffffff8108c139>]  [<ffffffff8108c139>] task_numa_fault+0x1a9/0x1e0
RSP: 0018:ffff880372237ba8  EFLAGS: 00010246
RAX: 0000000000000074 RBX: 0000000000000001 RCX: 0000000000000001
RDX: 00000000000012ae RSI: 0000000000000004 RDI: 00007faf4fc01000
RBP: ffff880372237be8 R08: 0000000000000000 R09: ffff8803657463f0
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000012
R13: ffff880372210d00 R14: 0000000000010088 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88037fc80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000001d26fec CR3: 000000000169f000 CR4: 00000000000027e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process ksmd (pid: 116, threadinfo ffff880372236000, task ffff880372210d00)
Stack:
 ffffea0016026c58 00007faf4fc00000 ffff880372237c48 0000000000000001
 00007faf4fc01000 ffffea000d6df928 0000000000000001 ffffea00166e9268
 ffff880372237c48 ffffffff8113cd0e ffff880300000001 0000000000000002
Call Trace:
 [<ffffffff8113cd0e>] __do_numa_page+0xde/0x160
 [<ffffffff8113de9e>] handle_pte_fault+0x32e/0xcd0
 [<ffffffffa01c22c0>] ? drop_large_spte+0x30/0x30 [kvm]
 [<ffffffffa01bf215>] ? kvm_set_spte_hva+0x25/0x30 [kvm]
 [<ffffffff8113eab9>] handle_mm_fault+0x279/0x760
 [<ffffffff8115c024>] break_ksm+0x74/0xa0
 [<ffffffff8115c222>] break_cow+0xa2/0xb0
 [<ffffffff8115e38c>] ksm_scan_thread+0xb5c/0xd50
 [<ffffffff810771c0>] ? wake_up_bit+0x40/0x40
 [<ffffffff8115d830>] ? run_store+0x340/0x340
 [<ffffffff8107692e>] kthread+0xce/0xe0
 [<ffffffff81076860>] ? kthread_freezable_should_stop+0x70/0x70
 [<ffffffff814fa7ac>] ret_from_fork+0x7c/0xb0
 [<ffffffff81076860>] ? kthread_freezable_should_stop+0x70/0x70
Code: 89 f0 41 bf 01 00 00 00 8b 1c 10 e9 d7 fe ff ff 8d 14 09 48 63 d2 eb bd 66 2e 0f 1f 84 00 00 00 00 00 49 8b 85 98 07 00 00 eb 91 <0f> 0b eb fe 80 3d 9c 3b 6b 00 01 0f 84 be fe ff ff be 42 09 00
RIP  [<ffffffff8108c139>] task_numa_fault+0x1a9/0x1e0
 RSP <ffff880372237ba8>
---[ end trace 9584c9b03fc0dbc0 ]---

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