구차니의 잡동사니 모음

$ LD_SHOW_AUXV=1 ls

AT_HWCAP:    half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt

AT_PAGESZ:       4096

AT_CLKTCK:       100

AT_PHDR:         0x10034

AT_PHENT:        32

AT_PHNUM:        9

AT_BASE:         0x76fae000

AT_FLAGS:        0x0

AT_ENTRY:        0x13a6d

AT_UID:          1000

AT_EUID:         1000

AT_GID:          1000

AT_EGID:         1000

AT_SECURE:       0

AT_RANDOM:       0x7eb85e2f

AT_HWCAP2:       0x0

AT_EXECFN:       /bin/ls

AT_PLATFORM:     v7l 

    *** At least one emulation must be selected ***

[*] VFP-format floating point maths                

[ ]   Advanced SIMD (NEON) Extension support     

$ LD_SHOW_AUXV=1 ls

AT_HWCAP:    half thumb fastmult vfp edsp vfpv3 tls vfpv4 idiva idivt

AT_PAGESZ:       4096

AT_CLKTCK:       100

AT_PHDR:         0x10034

AT_PHENT:        32

AT_PHNUM:        9

AT_BASE:         0x76f84000

AT_FLAGS:        0x0

AT_ENTRY:        0x13a6d

AT_UID:          1000

AT_EUID:         1000

AT_GID:          1000

AT_EGID:         1000

AT_SECURE:       0

AT_RANDOM:       0x7edf9e2f

AT_HWCAP2:       0x0

AT_EXECFN:       /bin/ls

AT_PLATFORM:     v7l 

$ cat /proc/cpuinfo

processor       : 0

model name      : ARMv7 Processor rev 5 (v7l)

BogoMIPS        : 38.40

Features        : half thumb fastmult vfp edsp vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm

CPU implementer : 0x41

CPU architecture: 7

CPU variant     : 0x0

CPU part        : 0xc07

CPU revision    : 5 

Yes Dalvik makes Jazelle useless. The only question is was Jazelle useful to begin with or is it 90% marketing hype? A good JIT or AOT(ahead of Time) compiler tends to give much better performance than trying to use specialized instructions. The register based approach of Dalvik might be faster than a traditional java bytecode interpreter but if the difference in minor between that of an interpreter and that of a JIT. Hopefully one of the next versions of Android has a JIT.

It takes ~5-10 years to write a good virtual machine with state of the art garbage collectors and optimizers. Sun (and Microsoft) have spent those years. Google hasn't. Hopefully they will keep investing in it so that one day Android Java code isn't a 90% slower than it should be.

[링크 : http://stackoverflow.com/questions/1153076/does-android-castrate-the-arms-jazelle-technology] 

There are (at least) 4 different ways of executing Java:

1. interpretation

2. direct hardware execution

3. JIT compilation

4. AOT compilation

In order to answer your question of whether an ARM core with Jazelle

would improve performance you first need to state what you are

currently using, which core and what speed. If you use an interpreter,

anything will give a good speedup.

Note there are 2 versions of Jazelle: DBX which executes byte codes

directly (various ARM9's and all ARM11's support this). This gives

around 4x speedup over interpretation and has no memory or startup

overheads. There is also an optimizer which can improve performance

at runtime. However rather than generating native instructions like a

JIT, it optimizes the bytecode itself.

Jazelle-RCT supports either JIT or AOT compilation into the Thumb-2EE

instruction set (Cortex-A8/Cortex-A9). This gives near native performance

but when using a JIT you get the usual startup and memory overheads

(although far less than when using x86 due to ARM's better code density).

[링크 : http://www.embeddedrelated.com/showthread/comp.arch.embedded/109371-1.php] 

CONFIG_BLK_DEV_INITRD=y

CONFIG_INITRAMFS_SOURCE="../target_fs"

[링크 : https://github.com/raspberrypi/linux/blob/rpi-patches/arch/arm/configs/bcmrpi_emergency_defconfig] 

[    2.465182] RAMDISK: lzma image found at block 0

[    2.469881] RAMDISK: lzma decompressor not configured!

[    2.475016] Invalid ramdisk decompression routine.  Select appropriate config option.

[    2.482897] Kernel panic - not syncing: Could not decompress initial ramdisk image.

-*- Kernel->user space relay support (formerly relayfs)           

[*] Initial RAM filesystem and RAM disk (initramfs/initrd) support

()    Initramfs source file(s)                                    

[*]   Support initial ramdisks compressed using gzip              

[ ]   Support initial ramdisks compressed using bzip2             

[ ]   Support initial ramdisks compressed using LZMA              

[ ]   Support initial ramdisks compressed using XZ                

[ ]   Support initial ramdisks compressed using LZO               

[ ]   Support initial ramdisks compressed using LZ4               

[ ] Optimize for size                                             

-*- Configure standard kernel features (expert users)  --->       

[*] Embedded system                                               

    Kernel Performance Events And Counters  --->                  

[*] Enable VM event counters for /proc/vmstat                     

[*] Enable SLUB debugging support                                 

2015/04/14 - [개소리 왈왈/라즈베리 파이 2] - 라즈베리 파이 2 커널 바꿔치기.. 실패 ㅠㅠ

$ file *

COPYING.linux:          Pascal source, ASCII text

LICENCE.broadcom:       ASCII text

a:                      directory

b:                      directory

bcm2708-rpi-b-plus.dtb: data

bcm2708-rpi-b.dtb:      data

bootcode.bin:           data

cmdline.txt:            ASCII text

config.txt:             ASCII text

fixup.dat:              data

fixup_cd.dat:           data

fixup_x.dat:            data

initrd.img:             LZMA compressed data, streamed

kernel.img:             Linux kernel ARM boot executable zImage (little-endian)

kernel7.img:            Linux kernel ARM boot executable zImage (little-endian)

overlays:               directory

snappy-system.txt:      ASCII text, with very long lines

start.elf:              ELF 32-bit LSB  executable, version 1 (SYSV), statically linked, stripped

start_cd.elf:           ELF 32-bit LSB  executable, version 1 (SYSV), statically linked, stripped

start_x.elf:            ELF 32-bit LSB  executable, version 1 (SYSV), statically linked, stripped

uEnv.txt:               empty

2015/04/14 - [개소리 왈왈/라즈베리 파이 2] - 라즈베리 파이 2 - RootFS in linux 

Uncompressing Linux... done, booting the kernel.

[    0.000000] Booting Linux on physical CPU 0xf00

[    0.000000] Initializing cgroup subsys cpu

[    0.000000] Initializing cgroup subsys cpuacct

[    0.000000] Linux version 3.18.10-v7+ (minimonk@devdesk) (gcc version 4.8.3 20140106 (prerelease) (crosstool-NG linaro-1.13.1-4.8-2014.01 - Linaro GCC 2013.11) ) #4 SMP PREEMPT Tue Apr 28 21:20:55 KST 2015

[    0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=10c5387d

[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache

[    0.000000] Machine: BCM2709

[    0.000000] cma: Reserved 8 MiB at 0x39800000

[    0.000000] Memory policy: Data cache writealloc

[    0.000000] [bcm2709_smp_init_cpus] enter (8620->f3003010)

[    0.000000] [bcm2709_smp_init_cpus] ncores=4

[    0.000000] PERCPU: Embedded 10 pages/cpu @ba369000 s11456 r8192 d21312 u40960

[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 239776

[    0.000000] Kernel command line: dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 bcm2709.boardrev=0xa21041 bcm2709.serial=0xa37ce24e smsc95xx.macaddr=B8:27:EB:7C:E2:4E bcm2708_fb.fbswap=1 bcm2709.disk_led_gpio=47 bcm2709.disk_led_active_low=0 sdhci-bcm2708.emmc_clock_freq=250000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000  dwc_otg.lpm_enable=0 console=ttyAMA0,115200 root=/dev/disk/by-label/system-a init=/lib/systemd/systemd ro panic=-1 fixrtc elevator=deadline rootwait

[    0.000000] PID hash table entries: 4096 (order: 2, 16384 bytes)

[    0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)

[    0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)

[    0.000000] Memory: 928208K/966656K available (5717K kernel code, 397K rwdata, 1748K rodata, 388K init, 763K bss, 38448K reserved)

[    0.000000] Virtual kernel memory layout:

[    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)

[    0.000000]     fixmap  : 0xffc00000 - 0xffe00000   (2048 kB)

[    0.000000]     vmalloc : 0xbb800000 - 0xff000000   (1080 MB)

[    0.000000]     lowmem  : 0x80000000 - 0xbb000000   ( 944 MB)

[    0.000000]     modules : 0x7f000000 - 0x80000000   (  16 MB)

[    0.000000]       .text : 0x80008000 - 0x8075287c   (7467 kB)

[    0.000000]       .init : 0x80753000 - 0x807b4000   ( 388 kB)

[    0.000000]       .data : 0x807b4000 - 0x8081747c   ( 398 kB)

[    0.000000]        .bss : 0x8081747c - 0x808d61d4   ( 764 kB)

[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1

[    0.000000] Preemptible hierarchical RCU implementation.

[    0.000000] NR_IRQS:608

[    0.000000] Architected cp15 timer(s) running at 19.20MHz (virt).

[    0.000014] sched_clock: 56 bits at 19MHz, resolution 52ns, wraps every 3579139424256ns

[    0.000036] Switching to timer-based delay loop, resolution 52ns

[    0.000313] Console: colour dummy device 80x30

[    0.000349] Calibrating delay loop (skipped), value calculated using timer frequency.. 38.40 BogoMIPS (lpj=192000)

[    0.000377] pid_max: default: 32768 minimum: 301

[    0.000780] Mount-cache hash table entries: 2048 (order: 1, 8192 bytes)

[    0.000803] Mountpoint-cache hash table entries: 2048 (order: 1, 8192 bytes)

[    0.002046] Initializing cgroup subsys memory

[    0.002097] Initializing cgroup subsys devices

[    0.002126] Initializing cgroup subsys freezer

[    0.002152] Initializing cgroup subsys net_cls

[    0.002175] Initializing cgroup subsys blkio

[    0.002278] CPU: Testing write buffer coherency: ok

[    0.002361] ftrace: allocating 19590 entries in 58 pages

[    0.050685] missing device node for CPU 0

[    0.050723] missing device node for CPU 1

[    0.050737] missing device node for CPU 2

[    0.050747] missing device node for CPU 3

[    0.050769] CPU0: thread -1, cpu 0, socket 15, mpidr 80000f00

[    0.050784] [bcm2709_smp_prepare_cpus] enter

[    0.050914] Setting up static identity map for 0x527b38 - 0x527b6c

[    0.110660] [bcm2709_boot_secondary] cpu:1 started (0) 18

[    0.110951] CPU1: Booted secondary processor

[    0.110960] [bcm2709_secondary_init] enter cpu:1

[    0.111014] CPU1: thread -1, cpu 1, socket 15, mpidr 80000f01

[    0.130645] [bcm2709_boot_secondary] cpu:2 started (0) 18

[    0.130881] CPU2: Booted secondary processor

[    0.130889] [bcm2709_secondary_init] enter cpu:2

[    0.130922] CPU2: thread -1, cpu 2, socket 15, mpidr 80000f02

[    0.150692] [bcm2709_boot_secondary] cpu:3 started (0) 16

[    0.150917] CPU3: Booted secondary processor

[    0.150924] [bcm2709_secondary_init] enter cpu:3

[    0.150955] CPU3: thread -1, cpu 3, socket 15, mpidr 80000f03

[    0.151048] Brought up 4 CPUs

[    0.151080] SMP: Total of 4 processors activated (153.60 BogoMIPS).

[    0.151091] CPU: All CPU(s) started in SVC mode.

[    0.152103] devtmpfs: initialized

[    0.176863] VFP support v0.3: implementor 41 architecture 2 part 30 variant 7 rev 5

[    0.178817] pinctrl core: initialized pinctrl subsystem

[    0.179596] NET: Registered protocol family 16

[    0.185269] DMA: preallocated 4096 KiB pool for atomic coherent allocations

[    0.186386] bcm2709.uart_clock = 3000000

[    0.188734] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers.

[    0.188751] hw-breakpoint: maximum watchpoint size is 8 bytes.

[    0.188783] mailbox: Broadcom VideoCore Mailbox driver

[    0.188890] bcm2708_vcio: mailbox at f300b880

[    0.189253] bcm_power: Broadcom power driver

[    0.189270] bcm_power_open() -> 0

[    0.189282] bcm_power_request(0, 8)

[    0.689968] bcm_mailbox_read -> 00000080, 0

[    0.689981] bcm_power_request -> 0

[    0.690104] Serial: AMBA PL011 UART driver

[    0.690236] dev:f1: ttyAMA0 at MMIO 0x3f201000 (irq = 83, base_baud = 0) is a PL011 rev3

[    1.195351] console [ttyAMA0] enabled

[    1.263851] SCSI subsystem initialized

[    1.267829] usbcore: registered new interface driver usbfs

[    1.273468] usbcore: registered new interface driver hub

[    1.278913] usbcore: registered new device driver usb

[    1.285800] Switched to clocksource arch_sys_counter

[    1.321396] FS-Cache: Loaded

[    1.324590] CacheFiles: Loaded

[    1.338877] NET: Registered protocol family 2

[    1.344505] TCP established hash table entries: 8192 (order: 3, 32768 bytes)

[    1.351730] TCP bind hash table entries: 8192 (order: 4, 65536 bytes)

[    1.358404] TCP: Hash tables configured (established 8192 bind 8192)

[    1.364854] TCP: reno registered

[    1.368114] UDP hash table entries: 512 (order: 2, 16384 bytes)

[    1.374078] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes)

[    1.380781] NET: Registered protocol family 1

[    1.385842] RPC: Registered named UNIX socket transport module.

[    1.391762] RPC: Registered udp transport module.

[    1.396505] RPC: Registered tcp transport module.

[    1.401204] RPC: Registered tcp NFSv4.1 backchannel transport module.

[    1.408004] Trying to unpack rootfs image as initramfs...

[   14.839907] Freeing initrd memory: 12660K (ba393000 - baff0000) 

gpio -g write 16 1

dtoverlay=lirc-rpi,gpio_out_pin=16,gpio_in_pin=17,debug=on

dtoverlay=lirc-rpi,gpio_out_pin=25,gpio_in_pin=18

[링크 : https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=99085] 

File:   lirc-rpi-overlay.dtb

Info:   Configures lirc-rpi (Linux Infrared Remote Control for Raspberry Pi)

        Consult the module documentation for more details.

Load:   dtoverlay=lirc-rpi,<param>=<val>,...

Params: gpio_out_pin             GPIO pin for output (default "17")

        gpio_in_pin              GPIO pin for input (default "18")

        gpio_in_pull             Pull up/down/off on the input pin

                                 (default "down")

        sense                    Override the IR receive auto-detection logic:

                                   "1" = force active high

                                   "0" = force active low

                                   "-1" = use auto-detection

                                 (default "-1")

        softcarrier              Turn the software carrier "on" or "off"

                                 (default "on")

        invert                   "on" = invert the output pin (default "off")

        debug                    "on" = enable additional debug messages

                                 (default "off")

[링크 : https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=97314]