I am doing project on Pandaboard using Embedded Linux (UBUNTU 12.10 Server Prebuild image) to optimize boot time. I need techniques or tools through which I can find boot time and techniques to optimize the boot time. If anyone can help.
Just remove application which is not required from /etc/init.d/rc file also put echo after every process initialization and check which process is taking much time for starting,
if you find application which is taking more time then debug that application and so on.
There is program that can be helpful to know the approximate boot-up time. Check this link
Time Stamp.
First of all the best you have to do is to compile yourself your own made kernel, get the source on the internet and do a make xconfig and then unselected everythin you don't need.
In a second time create your own root filesystem using Buildroot and make xconfig to select/unselect everything you need or not.
Hope this help.
I had the same problem and do that way, now it's clearly not the same ;)
EDIT: Everything you need will be here
to analyze the boot process, you can use Bootchart2, its available on github: https://github.com/mmeeks/bootchart
or Bootchart, from the Ubuntu packages:
sudo apt-get update
sudo apt-get install bootchart pybootchartgui
There are broadly 3 areas where you can reduce boot time
Bootloader:
Modify the linker script to initialize only the required h/w. Also, if you are using an SD card to boot, merge kernel and bootloader image to save time.
Kernel:
Remove unwanted modules from kernel config. Also try using compressed and uncompressed image. If your CPU is good enough to handle it go compressed image and check uncompression time required for different compression types.
Filesystem:
FS size can be significantly reduced by removing the unwanted bins and libs. Check for dependencies and use only the one's that are required.
For more techniques and information on tools that help in measuring the boot time please refer to the following link.
Refer to Training Material
The basic rule is: the fastest code is code that never gets loaded and
run, so remove everything you don't need:
in U-Boot: don't load and run the full U-Boot at all; use FALCON
mode and have the SPL load the Linux kernel and DTB directly
in Linux: remove all drivers and other stuff you don't really need;
load all drivers that are not essential for your core application as
modules - and load them after your application was started. If you
take this serious, you may even want to start only one CPU core
initially (and start the remaining ones after your application is
running).
in user space: minimize the size of the root file system. throuw
out anything you don't need; configure tools (like busybox) to
contain only the really needed functionality; use efficient code
(for example, link against musl libc instead of glibc) etc.
What can be acchieved by combining all these measures can be seen in
this video - and yes, the complete code for this optimization is
available here.
Optimizing embedded Linux Boot process , needs modifications in three level of embedded Linux design.
Note: you will need the source codes of bootloader and kernel
Boot : the first step in optimizing and reducing boot time of board is optimizing boot loader. first you should know what is your bootloader is. If your bootloader is an opensource bootloader like u-boot than you have the opportunity to modify and optimize it. In u-boot we have a procedure that we can skip unnecessary system check and just upload kernel image to ram and start. the documentation and instruction for this is available in u-boot website. by doing this you will save about 4 ~ 5 second in boot.
Kernel : for having a quicker kernel , you should optimize kernel in many sections. for editing you can use on of Linux config menu. I always use a low graphic menu. it need some dependency you can use it by this command:
$ make menuconfig
our goal for Linux kernel is to have smaller kernel image and less module to load in boot. first change the algorithm of compression from gzip to LZO. the point of this action is gzip algorithm will take much time to extract kernel. by using LZO we have a quicker kernel decompression process. the second , disable any unnecessary driver or module that you don’t have it on your board or you don’t use it any more. by doing this , you will lose some device access and cannot use them in Linux but you will have two positive points: less Ram usage , quicker boot time.
but please remind that some driver are necessary for Linux and by disabling them you will lose some of main features (for example if you disable I2C driver in Linux you will no longer have a HDMI interface) that you need or in worst case you will have a boot problem (such as boot-loop). The third is to disable some of unusable filesystem to reduce kernel size and boot time. The Fourth is to remove some of compression algorithm to have smaller kernel image.
the last thing , If you are using a u-boot bootloader create a uImage instead of zImage. the following steps , are general and main actions , for having quicker boot as 1 second after power attach you should change more option.
after two base layer modifications, now we should optimize boot process in user-space (root file system). depend on witch system are you using , we have different changes to do. in abstract root file system of Linux that have necessary package and system to boot Linux we should use systemd instead of Unix systemv , because systemd have a multi-task init. system and it is faster , after that is udev that you should modify some of loading modules. if you have a graphical user-interface , we can use an easy trick to have a big boot time reduction by initing GUI first and load other module after loading GUI.
if you do all of following tasks , you can have quick boot time and fast system to work with.
Related
I am working under linux and what I want to do is to lock cpu to a certain frequency, disable cpu automatic freq change.
Could anyone indicate how to do it in driver or kernel ?
Thanks.
what I want to do is to lock cpu to a certain frequency, disable cpu automatic freq change.
You can use kernel modules to do this for you already and there are user space programs that you can run to disable it. Look for Disable Frequency scaling.
on Debian the package can be installed as follows
aptitude install cpufrequtils
The read the docs from there. If you want to get a bit more hands by loading kernel modules, for Intel the one you need to load is...
acpi-cpufreq
If you're running Linux in something like a VirtualBox and trying to load this it will likely fail because acpi will be disabled. You can find out what you need to do here to control this from command line.
http://www.thinkwiki.org/wiki/How_to_make_use_of_Dynamic_Frequency_Scaling
If you want to see how this is done in a kernel module the source code you need can be found here.
http://lxr.free-electrons.com/source/drivers/cpufreq/acpi-cpufreq.c
You would likely need to read the source for one of the governor modules to understand how this works.
If possible I'd control this from userspace.
I'm working with ELinux kernel on ARM cortex-A8.
I know how the bootloader works and what job it's doing. But i've got a question - why do we need bootloader, why was the bootloader born?
Why we can't directly load the kernel into RAM from flash memory without bootloader? If we load it what will happen? In fact, processor will not support it, but why are we following the procedure?
In the context of Linux, the boot loader is responsible for some predefined tasks. As this question is arm tagged, I think that ARM booting might be a useful resource. Specifically, the boot loader was/is responsible for setting up an ATAG list that describing the amount of RAM, a kernel command line, and other parameters. One of the most important parameters is the machine type. With device trees, an entire description of the board is passed. This makes a stock ARM Linux impossible to boot with out some code to setup the parameters as described.
The parameters allows one generic Linux to support multiple devices. For instance, an ARM Debian kernel can support hundreds of different board types. Uboot or other boot loader can dynamically determine this information or it can be hard coded for the board.
You might also like to look at bootloader info page here at stack overflow.
A basic system might be able to setup ATAGS and copy NOR flash to SRAM. However, it is usually a little more complex than this. Linux needs RAM setup, so you may have to initialize an SDRAM controller. If you use NAND flash, you have to handle bad blocks and the copy may be a little more complex than memcpy().
Linux often has some latent driver bugs where a driver will assume that a clock is initialized. For instance if Uboot always initializes an Ethernet clock for a particular machine, the Linux Ethernet driver may have neglected to setup this clock. This can be especially true with clock trees.
Some systems require boot image formats that are not supported by Linux; for example a special header which can initialize hardware immediately; like configuring the devices to read initial code from. Additionally, often there is hardware that should be configured immediately; a boot loader can do this quickly whereas the normal structure of Linux may delay this significantly resulting in I/O conflicts, etc.
From a pragmatic perspective, it is simpler to use a boot loader. However, there is nothing to prevent you from altering Linux's source to boot directly from it; although it maybe like pasting the boot loader code directly to the start of Linux.
See Also: Coreboot, Uboot, and Wikipedia's comparison. Barebox is a lesser known, but well structured and modern boot loader for the ARM. RedBoot is also used in some ARM systems; RedBoot partitions are supported in the kernel tree.
A boot loader is a computer program that loads the main operating system or runtime environment for the computer after completion of the self-tests.
^ From Wikipedia Article
So basically bootloader is doing just what you wanted - copying data from flash into operating memory. It's really that simple.
If you want to know more about boostrapping the OS, I highly recommend you read the linked article. Boot phase consists, apart from tests, also of checking peripherals and some other things. Skipping them makes sense only on very simple embedded devices, and that's why their bootloaders are even simpler:
Some embedded systems do not require a noticeable boot sequence to begin functioning and when turned on may simply run operational programs that are stored in ROM.
The same source
The primary bootloader is usually built in into the silicon and performs the load of the first USER code that will be run in the system.
The bootloader exists because there is no standardized protocol for loading the first code, since it is chip dependent. Sometimes the code can be loaded through a serial port, a flash memory, or even a hard drive. It is bootloader function to locate it.
Once the user code is loaded and running, the bootloader is no longer used and the correctness of the system execution is user responsibility.
In the embedded linux chain, the primary bootloader will setup and run the Uboot. Then Uboot will find the linux kernel and load it.
Why we can't directly load the kernel into RAM from flash memory without bootloader? If we load it what will happen? In fact, processor will not support it, but why are we following the procedure?
Bartek, Artless, and Felipe all give parts of the picture.
Every embedded processor type (E.G. 386EX, Coretex-A53, EM5200) will do something automatically when it is reset or powered on. Sometimes that something is different depending on whether the power is cycled or the device is reset. Some embedded processors allow you to change that something based on voltages applied to different pins when the device is powered or reset.
Regardless, there is a limited amount of something that a processor can do, because of the physical space on-processor required to define that something, whether it is on-chip FLASH, instruction micro-code, or some other mechanism.
This limit means that the something is
fixed purpose, does one thing as quickly as possible.
limited in scope and capability, typically loading a small block of code (often a few kilobytes or less) into a fixed memory location and executing from the start of the loaded code.
unmodifiable.
So what a processor does in response to reset or power-cycle cannot be changed, and cannot do very much, and we don't want it to automatically copy hundreds of megabytes or gigabytes into memory which may not exist or may not be initialized, and which could take a looooong time.
So....
We set up a small program which is smaller than the smallest size permitted across all of the devices we are going to use. That program is stored wherever the something needs it to be.
Sometimes the small program is U-Boot. Sometimes even U-Boot is too big for initial load, so the small program then in turn loads U-Boot.
The point is that whatever gets loaded by the something, is modifiable as needed for a particular system. If it is U-Boot, great, if not, it knows where to load the main operating system or where to load U-Boot (or some other bootloader).
U-Boot (speaking of bootloaders in general) then configures a minimal set of devices, memory, chip settings, etc., to enable the main OS to be loaded and started. The main OS init takes care of any additional configuration or initialization.
So the sequence is:
Processor power-on or reset
Something loads initial boot code (or U-Boot style embedded bootloader)
Initial boot code (may not be needed)
U-Boot (or other general embedded bootloader)
Linux init
The kernel requires the hardware on which you are working to be in a particular state. All the hardware you used needs to be checked for its state and initialized for its further operation. This is one of the main reasons to use a boot loader in an embedded (or any other environment), apart from its use to load a kernel image into the RAM.
When you turn on a system, the RAM is also not in a useful state (fully initialized to use) for us to load kernel into it. Therefore, we cannot load a kernel directly (to answer your question)and thus arises the need for a construct to initialize it.
Apart from what is stated in all the other answers - which is correct - in some cases the system has to go through different execution modes, take as example TrustZone for secure ARM chips. It is possible to still consider it as sort of HW initialization, but what makes it peculiar is the fact that there are additional limitations (ex: memory available) that make it impractical, if not impossible, to do everything in a single binary, thus multiple stages of bootloader are available.
Furthermore, for security reason, each of them is signed and can perform its job only if it meets the security requirements.
In my ARM based custom board, I flash u-boot to NAND whenever I do changes on that. (putting some debug statements/modification). Is there any way to directly load the uboot image in RAM memory instead of flashing it every time?
For linux kernel image I do load it in memory and use bootm to boot that image. Similarly for u-boot I am trying out. Kindly provide your suggestions.
Someone at Freescale has done this, for their P1022DS evaluation system (and some others as well). They have provided a somewhat useful document about the process in the file ${UBOOTROOT}/doc/README.ramboot-ppc8500 (in U-Boot V2010.12). This document is pretty terse and leaves many questions unanswered, but I found it a reasonable place to start when I needed to debug U-Boot for a new board, before the flash memory for that board was operating correctly.
In fact, having non-functional flash memory is one reason you might want to debug U-Boot in RAM. (There are a few reasons listed in the README, and they all sound pretty reasonable to me, in contrast to some of the other advice available on this subject)
In our situation, it was found that early prototype target board hardware included an error in the address bus connection to the flash memory that prevented us from using that flash memory. While the hardware was being redesigned and re-fabricated, we wanted to continue testing/debugging those parts of our U-Boot configuration that did not depend on flash memory, for example, I2C, Ethernet, FPGA configuration, PCIe, etc. (there are plenty of things that are independent of where the U-Boot image comes from).
Running U-Boot after loading it into RAM via a JTAG interface (using Codewarrior and the USB TAP) allowed us to continue our U-Boot bring-up tasks, even though we had no functional flash memory. Once we received a newer version of the target board with correctly functioning flash memory, we returned to debugging those parts of U-Boot that we hadn't been able to test earlier. After that, U-Boot was fully functional, and we did not have to wait for a board spin to make any progress.
Debugging a bootloader is a bit difficult, but with the right tools it should be relatively painless.
I deal with the PowerPC achitecture and with a BDI-3000 I can load and debug directly to RAM (of course, after initializing the DDR controller).
One option is if you have on-chip SRAM or L2 Cache that can be configured as on-chip SRAM. The BDI can copy to the SRAM area first, u-boot does it's thing (initialize DDR controller for example), then relocates itself to DDR RAM afterwards. Definitely faster that re-writing to slow Flash all the time.
It wasn't possible in 2004, at least.
It should be possible, if the U-Boot image you want to run has startup code that allows running it from arbitrary addresses. Whether or not that is the case for your board I can't tell.
If the startup code begins by copying the code section from the current (PC-relative) address to the final execution address (usually this is preceded by a check that these areas don't overlap), then you can load the .bin file to any address in RAM, and invoke it using go.
The second obstacle I could see would be unconditional RAM setup code at the beginning, which a number of boards have.
This is what can be read on the u-boot documentation FAQ:
Question:
I don't want to erase my flash memory because I'm not sure if my new U-Boot image will work. Is it possible to configure U-Boot such
that I can load it into RAM instead of flash, and start it from my old
boot loader?
Answer:
No. (Unless you're using a Blackfin processor, or Socfpga board, but you probably aren't.)
Question:
But I've been told it is possible??
Answer:
Well, yes. Of course this is possible. This is software, so everything is possible. But it is difficult, unsupported, and fraught
with peril. You are on your own if you choose to do it. And it will
not help you to solve your problem.
source:http://www.denx.de/wiki/view/DULG/CanUBootBeConfiguredSuchThatItCanBeStartedInRAM
The problem here is that what you are trying to do goes against the philosophy of what a bootloader is. Most processors require that code starts from Flash. That code is called a bootloader. That is what U-boot is.
However, if you want to modify U-boot so that it is not a true bootloader, then you can do whatever you want. It's just software. But don't expect any mainline support for the above reasons.
Just take in mind (be care of) the hardware that you are configuring in your modified U-Boot. U
Boot is intended to initialize critical modules, some of them are not able to be re-configured on the fly or they may not performe as if they were initialized/configured at startup.
If your Target board support network booting, you can load uboot image from host machine to RAM through network.
You can use usb boot. TI and Freescale provides their usb boot utilities. I don't know about other vendors.
Yes, It is possible most of the compilation structure at the end U-Boot provides a u-boot.bin file which is a flattened binary, if your target supports USB/TFTP or any other medium which current U-boot can detect on you target environment then we can load the u-boot.bin file to the static memory address area. This address is the entry point of U-Boot Code and U-boot can execute the flattened binaries by go 0x<memory_address>. The static memory address area can be deduced form u-boot.map file, This entry point is basically address to the .text area of compiled program usually can we searched in the .map file with string "Address of section .text set to 0x." Below is the example of doing it from USB.
usb start
load usb 0x<memory_address> u-boot.bin
go 0x<memory_address>
This should run you U-Boot from usb with out disturbing current code.
I recently read a post (admittedly its a few years old) and it was advice for fast number-crunching program:
"Use something like Gentoo Linux with 64 bit processors as you can compile it natively as you install. This will allow you to get the maximum punch out of the machine as you can strip the kernel right down to only what you need."
can anyone elaborate on what they mean by stripping down the kernel? Also, as this post was about 6 years old, which current version of Linux would be best for this (to aid my google searches)?
There is some truth in the statement, as well as something somewhat nonsensical.
You do not spend resources on processes you are not running. So as a first instance I would try minimise the number of processes running. For that we quite enjoy Ubuntu server iso images at work -- if you install from those, log in and run ps or pstree you see a thing of beauty: six or seven processes. Nothing more. That is good.
That the kernel is big (in terms of source size or installation) does not matter per se. Many of this size stems from drivers you may not be using anyway. And the same rule applies again: what you do not run does not compete for resources.
So think about a headless server, stripped down -- rather than your average desktop installation with more than a screenful of processes trying to make the life of a desktop user easier.
You can create a custom linux kernel for any distribution.
Start by going to kernel.org and downloading the latest source. Then choose your configuration interface (you have the choice of console text, 'config', ncurses style 'menuconfig', KDE style 'xconfig' and GNOME style 'gconfig' these days) and execute ./make whateverconfig. After choosing all the options, type make to create your kernel. Then make modules to compile all the selected modules for this kernel. Then, make install will copy the files to your /boot directory, and make modules_install, copies the modules. Next, go to /boot and use mkinitrd to create the ram disk needed to boot properly, if needed. Then you'll add the kernel to your GRUB menu.lst, by editing menu.lst and copying the latest entry and adding a similar one pointing to the new kernel version.
Of course, that's a basic overview and you should probably search for 'linux kernel compile' to find more detailed info. Selecting the necessary kernel modules and options takes a bit of experience - if you choose the wrong options, the kernel might not be bootable and you'll have to start over, which is a pain because selecting the options and compiling the kernel can take 15-30 minutes.
Ultimately, it isn't going to make a large difference to compile a stripped-down custom kernel unless your given task is very, very performance sensitive. It makes sense to remove things you're never going to use from the kernel, though, like say ISDN support.
I'd have to say this question is more suited to SuperUser.com, by the way, as it's not quite about programming.
Can anyone point me to a good tutorial on creating a bootable Linux CD from scratch?
I need help with a fairly specialized problem: my firm sells an expansion card that requires custom firmware. Currently we use an extremely old live CD image of RH7.2 that we update with current firmware. Manufacturing puts the cards in a machine, boots off the CD, the CD writes the firmware, they power off and pull the cards. Because of this cycle, it's essential that the CD boot and shut down as quickly as possible.
The problem is that with the next generation of cards, I have to update the CD to a 2.6 kernel. It's easy enough to acquire a pre-existing live CD - but those all are designed for showing off Linux on the desktop - which means they take forever to boot.
Can anyone fix me up with a current How-To?
Update:
So, just as a final update for anyone reading this later - the tool I ended up using was "livecd-creator".
My reason for choosing this tool was that it is available for RedHat-based distributions like CentOs, Fedora and RHEL - which are all distributions that my company supports already. In addition, while the project is very poorly documented it is extremely customizable. I was able to create a minimal LiveCD and edit the boot sequence so that it booted directly into the firmware updater instead of a bash shell.
The whole job would have only taken an hour or two if there had been a README explaining the configuration file!
There are a couple of interesting projects you could look into.
But first: does it have to be a CD-ROM? That's probably the slowest possible storage (well, apart from tape, maybe) you could use. What about a fast USB stick or a an IEE1394 hard-disk or maybe even an eSATA hard-disk?
Okay, there are several Live-CDs that are designed to be very small, in order to e.g. fit on a business card sized CD. Some were also designed to be booted from a USB stick, back when that meant 64-128 MiByte: Damn Small Linux is one of the best known ones, however it uses a 2.4 kernel. There is a sister project called Damn Small Linux - Not, which has a 2.6 kernel (although it seems it hasn't been updated in years).
Another project worth noting is grml, a Live-CD for system administration tasks. It does not boot into a graphic environment, and is therefore quite fast; however, it still contains about 2 GiByte of software compressed onto a CD-ROM. But it also has a smaller flavor, aptly named grml-small, which only contains about 200 MiByte of software compressed into 60 MiByte.
Then there is Morphix, which is a Live-CD builder toolkit based on Knoppix. ("Morphable Knoppix"!) Morphix is basically a tool to build your own special purpose Live-CD.
The last thing I want to mention is MachBoot. MachBoot is a super-fast Live-CD. It uses various techniques to massively speed up the boot process. I believe they even trace the order in which blocks are accessed during booting and then remaster the ISO so that those blocks are laid out contiguously on the medium. Their current record is less than 6 seconds to boot into a full graphical desktop environment. However, this also seems to be stale.
One key piece of advice I can give is that most LiveCDs use a compressed filesystem called squashfs to cram as much data on the CD as possible. Since you don't need compression, you could run the mksquashfs step (present in most tutorials) with -noDataCompression and -noFragmentCompression to save on decompression time. You may even be able to drop the squashfs approach entirely, but this would require some restructuring. This may actually be slower depending on your CD-ROM read speed vs. CPU speed, but it's worth looking into.
This Ubuntu tutorial was effective enough for me to build a LiveCD based on 8.04. It may be useful for getting the feel of how a LiveCD is composed, but I would probably not recommend using an Ubuntu LiveCD.
If at all possible, find a minimal LiveCD and build up with only minimal stripping out, rather than stripping down a huge LiveCD like Ubuntu. There are some situations in which the smaller distros are using smaller/faster alternatives rather than just leaving something out. If you want to get seriously hardcore, you could look at Linux From Scratch, and include only what you want, but that's probably more time than you want to spend.
Creating Your Own Custom Ubuntu 7.10 Or Linux Mint 4.0 Live-CD With Remastersys
Depends on your distro. Here's a good article you can check out from LWN.net
There is a book I used which covers a lot of distros, though it does not cover creating a flash-bootable image. The book is Live Linux(R) CDs: Building and Customizing Bootables. You can use it with supplemental information from your distro of choice.
So, just as a final update for anyone reading this later - the tool I ended up using was "livecd-creator".
My reason for choosing this tool was that it is available for RedHat-based distributions like CentOs, Fedora and RHEL - which are all distributions that my company supports already. In addition, while the project is very poorly documented it is extremely customizable. I was able to create a minimal LiveCD and edit the boot sequence so that it booted directly into the firmware updater instead of a bash shell.
The whole job would have only taken an hour or two if there had been a README explaining the configuration file!
Debian Live provides the best tools for building a Linux Live CD. Webconverger uses Debian Live for example.
It's very easy to use.
sudo apt-get install live-helper # from Debian unstable, which should work fine from Ubuntu
lh_config # edit config/* to your liking
sudo lh_build