我使用linux perf工具收集程序的分支信息，命令和结果如下：
$ sudo perf record -b /bin/ls
Error:
No hardware sampling interrupt available.
No APIC? If so then you can boot the kernel with the "lapic" boot parameter to force-enable it.
/pro/cpuinfo 中的内容如下：
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5405 @ 2.00GHz
stepping : 10
microcode : 0xa07
cpu MHz : 1994.921
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 **apic** sep mtrr pge mca cmov pat pse36 clflush dts acpi strong text mmx fxsr sse sse2 ss ht tm
pbe syscall nx lm constant_tsc arch_perfmon pebs **bts** rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx tm2 ssse3 cx16 xtpr pdcm
dca sse4_1 xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bugs :
bogomips : 3989.84
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management:
apic并且bts输入flags得到加强（我想要但只是被“**”封装）而且我不知道这种情况下还有什么重要的。其他 7 个处理器与处理器 0 相同。
通过修改 /boot/grub/grub.cfg 添加引导参数“lapic”：
menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-0ed8a872-4eb7-4339-a0bb-6c0033da582e' {
recordfail
load_video
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root='hd0,msdos1'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 ced80bc6-08a9-4909-9717-97658cf0c4fd
else
search --no-floppy --fs-uuid --set=root ced80bc6-08a9-4909-9717-97658cf0c4fd
fi
linux /vmlinuz-4.2.0-42-generic root=/dev/mapper/fedora_hustyong-root ro **lapic** quiet splash $vt_handoff
initrd /initrd.img-4.2.0-42-generic
}
只需添加条目lapic。linux
但是重启后没有任何意义。
我的问题：
1）错误信息是什么意思？
2) perf 工具分支采样是否使用 Intel Branch Trace Store(BTS)？还是最后一个分支记录（LBR）？
3) 如何查找 LBR 支持？
4) x86 32bit 和 64bit 之间的 LBR 和 BTS 支持有什么不同？
我的操作系统是Ubuntu 14.04 64bit：
$ uname -a
Linux user-S5000VSA 4.2.0-42-generic #49~14.04.1-Ubuntu SMP Wed Jun 29 20:22:11 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
perf 安装说明：
$ sudo apt-get install linux-tools-common
$ sudo apt-get install linux-tools-4.2.0-27-generic linux-cloud-tools-4.2.0-27-generic
更新：
/proc/interrupts 的内容：
CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7
0: 127780 52084 127784 126729 127706 128431 127785 126822 IO-APIC 2-edge timer
1: 52 42 3 2 62 49 5 2 IO-APIC 1-edge i8042
8: 0 0 0 0 0 0 0 1 IO-APIC 8-edge rtc0
9: 0 0 0 0 0 0 0 0 IO-APIC 9-fasteoi acpi
12: 1428 1307 52 47 1424 1324 53 58 IO-APIC 12-edge i8042
14: 0 0 0 0 0 0 0 0 IO-APIC 14-edge ata_piix
15: 0 0 0 0 0 0 0 0 IO-APIC 15-edge ata_piix
17: 47 276 1004 49 52 295 993 50 IO-APIC 17-fasteoi radeon
20: 31062 4201 7533 29935 31080 4297 7540 29824 IO-APIC 20-fasteoi ata_piix
22: 0 0 0 0 0 0 0 0 IO-APIC 22-fasteoi uhci_hcd:usb3, uhci_hcd:usb5
23: 0 0 0 0 0 0 0 0 IO-APIC 23-fasteoi ehci_hcd:usb1, uhci_hcd:usb2, uhci_hcd:usb4
25: 2 755654 3 3 1 1 3 6 PCI-MSI 2621440-edge eth0
27: 0 0 0 0 0 0 0 1 PCI-MSI 131072-edge ioat-msi
NMI: 6756 678 6894 5867 861 2168 4994 3700 Non-maskable interrupts
LOC: 343554 578094 1736638 773135 219952 777567 1459249 689292 Local timer interrupts
SPU: 0 0 0 0 0 0 0 0 Spurious interrupts
PMI: 6756 678 6894 5867 861 2168 4994 3700 Performance monitoring interrupts
IWI: 6756 678 6894 5867 861 2168 4994 3700 IRQ work interrupts
RTR: 0 0 0 0 0 0 0 0 APIC ICR read retries
RES: 82594 294601 142535 259797 77845 316210 84927 261455 Rescheduling interrupts
CAL: 4749 9296 7358 31330 7560 8564 5751 20364 Function call interrupts
TLB: 5933 2044 12867 11215 6563 4682 8669 8272 TLB shootdowns
TRM: 0 0 0 0 0 0 0 0 Thermal event interrupts
THR: 0 0 0 0 0 0 0 0 Threshold APIC interrupts
DFR: 0 0 0 0 0 0 0 0 Deferred Error APIC interrupts
MCE: 0 0 0 0 0 0 0 0 Machine check exceptions
MCP: 292 292 292 292 292 292 292 292 Machine check polls
HYP: 0 0 0 0 0 0 0 0 Hypervisor callback interrupts
ERR: 0
MIS: 0
PIN: 0 0 0 0 0 0 0 0 Posted-interrupt notification event
PIW: 0 0 0 0 0 0 0 0 Posted-interrupt wakeup event
我安装ubuntu 16.10 64bit在我的电脑上并perf record -b成功运行。我认为内核linux-tools-4.2.0-27-generic或linux-cloud-tools-4.2.0-27-generic包中可能有问题。