what is the difference b/w machine independent and machine neutral????
The words are different, the meaning is the same.
Namely: The bytecode produced can run on any machine that has the Java Runtime installed.
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I'm writing a program that manages data entered by users. I plan to open a test version to the public and have no idea how many users there may be.
I want my program to test when memory is getting low so that I know when to buy more server space and so that I can automatically restrict data entry when necessary. What's a good way to detect memory shortage? Allocate garbage space temporarily to get the exception? Is there a better way?
This may be best accomplished outside of your application using a performance monitoring tool. Windows Server can be configured to do this for you; see this question. There are other tools out there that help you monitor your servers, and I advise you to use an existing system unless you absolutely have to do this with Python.
If you must absolutely do this using Python, then have a look at the psutil library:
psutil (python system and process utilities) is a cross-platform
library for retrieving information on running processes and system
utilization (CPU, memory, disks, network) in Python. It is useful
mainly for system monitoring, profiling and limiting process resources
and management of running processes. It implements many
functionalities offered by command line tools such as: ps, top, lsof,
netstat, ifconfig, who, df, kill, free, nice, ionice, iostat, iotop,
uptime, pidof, tty, taskset, pmap. It currently supports Linux,
Windows, OSX, FreeBSD and Sun Solaris, both 32-bit and 64-bit
architectures, with Python versions from 2.4 to 3.4. Pypi is also
known to work.
You may combine this with the email package to send the alerts.
I am a Java developer. To speed some of our algorithms, we have decided to try CUDA.
But the Issue is, currently we have only one server with GPU installed and 3 developers have to work on it (by transferring the file each time over ssh and compiling and running it over there). This obviously is a tedious process.
What I would like to know is: On my machine which does not have GPU, can I using NSight work on CUDA by compiling and generating files locally. This can automatically be transferred to server to get the result.
If we can at least work on algorithm locally using NSight (or any other IDE) and not pure vim and then compile it to remove compile time errors, this would save quite some time.
On Linux you can do remote debugging using Nsight Eclipse Edition as documented here. This requires 5.5 or later. On Windows you need to start the Nsight monitor on the server and then just configure Nsight Visual Studio Edition to use the remote machine.
I am a fresh man in kvm,qemu-kvm and kvm are both very complicated now.
Anyone can introduce some primers about qemu-kvm and kvm?
thanks very much!
KVM stands for kernel based virtual machine. it enables you to create as many number of virtual machine as you like. These machine can be of two types LVM based or Non-LVM based.
Those machine which are LVM based you can take live backup for them. for non-lvm based VM you cannot take live backup i.e. they will be paused when you take backup for them. please refer KVM home page KVM Home Page.
QEMU is a generic and open source machine emulator and virtualizer.When used as a machine emulator, QEMU can run OSes and programs made for one machine (e.g. an ARM board) on a different machine (e.g. your own PC). By using dynamic translation, it achieves very good performance. When used as a virtualizer, QEMU achieves near native performances by executing the guest code directly on the host CPU. QEMU supports virtualization when executing under the Xen hypervisor or using the KVM kernel module in Linux. When using KVM, QEMU can virtualize x86, server and embedded PowerPC, and S390 guests.
For managing the KVM VM's you need to install Libvirt which is the virtualization library. It provides you the tools for starting, suspending, resuming, cloning, restarting, listing of virtual machine. Please refer Libvirt home page for more reference.
If you are working on some backup or recovery process then I suggest you to go through this excellent perl script as well it will give a fair idea of how the backup and snapshot is being taken for KVM VM's.
KVM based virtual machines are not complicated once you go through the theory of them and start implementing them. I believe once you start working on them you will find fun in managing them.
Putting in a nutshell
QEMU : An emulator which translates the instruction of guest operating system to host operating system. As you can guess that translation has a certain cost, you will not see Guest machine working as fast as host machine.
For more info see the QEMU wiki
KVM (Kernal Virtual Machine): A module in Kernel which support Virtual Machine (host operating system) in hardware. By support I mean that if your guest architecture is same as host architecture, then certainly there is no need to translate the instructions as they can directly be executed by host. For this modern hardware are equipped with special registers and storage location which is leveraged by KVM. Also KVM is a module, some driver is needed to use the KVM, which is qemu also.
For more info see the KVM section in the same wiki.
QEMU-KVM : As I above mentioned, KVM is a module only, qemu is needed (or other) to use KVM. When KVM is used with QEMU, control transfers from QEMU to KVM and vice-versa over the execution.
Talking about KVM is talking about virtualization technology or about kernel modules (kvm.ko, kvm-intel.ko or kvm-amd-ko). Sometimes KVM is mentioned as a virtual machine, this is not correct, because KVM does not provide virtualized hardware.
Source
I have access to a server machine, with 3 CUDA enabled GPUs in it, and I would like to use NVidia Parallel Nsight, to remotly debug on the machine.
This works just find.
Now, is it possibble, to start another debug session (possibbly by another developer), on the same machine, but on another GPGPU?
Is it possibble, to do this, if I use gdb on linux?
Thanks,
krisy
Krisy, yes this is possible.
However this case/scenario that you mentioned has not been actively tested internally by the Nsight team yet. I tried this our real quick on a system with a similar setup as the one you mentioned and I was able to debug 2 different instances of CUDA app simulataneously (provided each app runs on a different unique device that is not connected to any output display).
The stability of this is not guaranteed. From what I've tried so far, this worked for me and it should work in theory as well but there were instances where I experienced sluggish behavior on my system.
For other developers who are interested to know more about this, please take a look at: http://forums.nvidia.com/index.php?showtopic=201211
I'm reading a book which says there are these subsystems:
win32,os/2,posix,etc..
But I don't have any perceptual knowledge with these notations, can you explain it in short words?
I get the feeling the concept of a "subsystem" is somewhat ill-defined, or at least used with different meanings in different contexts.
According to MSDN documentation:
Environment subsystems are Windows NT processes that emulate different operating system environments. The Windows NT executive provides generic services that all environment subsystems can call to perform basic operating system functions.
Windows Internals book talks about the following two subsystems:
Windows subsystem of which it says - "this [subsystem] is special in that Windows can't run without it. (It owns the keyboard, mouse and display and it is required to be present even on server systems with no interactive users logged in. In fact the other two (which two?) subsystems are configured to start on demand, whereas the Windows subsystem must always be running."
Subsystem for Unix-based Applications, also known as SUA[POSIX] subsystem
Now, the /SUBSYSTEM option that can be sent to the Microsoft VS C++ linker in its documentation says and I quote
You can specify any of the following subsystems:
BOOT_APPLICATION
An application that runs in the Windows boot environment. For more information about boot applications, see About the BCD WMI Provider.
CONSOLE
A Windows character-mode application. The operating system provides a console for console applications.
Extensible Firmware Interface (EFI) Image
The EFI subsystem options describe executable images that run in the Extensible Firmware Interface environment. This environment is typically provided with the hardware and executes before the operating system is loaded. The major differences between EFI image types are the memory location that the image is loaded into and the action that's taken when the call to the image returns. An EFI_APPLICATION image is unloaded when control returns. An EFI_BOOT_SERVICE_DRIVER or EFI_RUNTIME_DRIVER is unloaded only if control returns with an error code. An EFI_ROM image is executed from ROM. For more information, see the specifications on the Unified EFI Forum website.
NATIVE
Code that runs without a subsystem environment—for example, kernel mode device drivers and native system processes. This option is usually reserved for Windows system features.
POSIX
An app that runs in the POSIX subsystem in Windows.
WINDOWS
An app that runs in the Windows graphical environment. This includes both desktop apps and Windows Store apps.
WINDOWSCE
The WINDOWSCE subsystem indicates that the app is intended to run on a device that has a version of the Windows CE kernel. Versions of the kernel include PocketPC, Windows Mobile, Windows Phone 7, Windows CE V1.0-6.0R3, and Windows Embedded Compact 7.
So there you go. Finally, people sometimes talk about the "Win32" subsystem, which I don't know if I should take to mean the "windows" subsystem or the "console" subsystem in the linker option sense.
Back to the Windows Internals book, it further says "each executable image (.exe) is bound to one and only one subsystem" which would explain the need to specify the subsystem your app is for at link-time.
Windows starting from NT (NT 3.1) is able to support semantics of different operating systems (or OS families) that existed at that time (1993). Microsoft called them Subsystems (today they would probably call them emulation layers).
When linking against a subsystem, it decides how your semantics will be. For the Win32 subsystem, for example, filenames are case insensitive (foo.txt and fOo.Txt refer to the same file) and device files (like con or nul) exist in every directory. For the POSIX subsystem, file names are case sensitive and device files exist only at one place. By linking existing (legacy) applications against a subsystem different from Win32, these apps "feel" more like the respective OSes and porting work is reduced.
If you want to know the subsystem of an EXE/DLL, you can open it in DependencyWalker - if it (directly or indirectly) depends on KERNEL32.DLL it is Win32 subsystem, if it (directly) depends on NTDLL.DLL it is native subsystem (Note that KERNEL32.DLL will itself depend on NTDLL.DLL, providing the compatibility layer for the Win32 subsystem).
This is mostly obsolete today. I say mostly as Microsoft included a new "Linux subsystem" in Windows 10 Anniversary update (which is a subsystem like Native, Win32 or POSIX), that behaves binary equivalent to Linux, making it easy to compile Linux applications to be run on Windows (or more precisely, its Linux subsystem).
The /SUBSYSTEM linker switch started out to do exactly the same, but was augmented with more options later (/SUBSYSTEM:CONSOLE also compiles for the Win32 subsystem but the application will allocate a console window if it did not inherit one from its parent process, /SUBSYSTEM:EFI_APPLICATION will compile an executable that cannot run on Windows at all, but will run in the Exensible Firmware Interface (EFI/UEFI) boot environment, etc.).
It might help if we knew which book you're referring to!
More generally, Win32 (which is 32-bit Windows, i.e. Windows NT 3.5 or later), OS/2 and the POSIX family are all operating systems. (POSIX is a standard family of APIs into the UNIX-like operating systems - see here for more.)
It sounds like what you describe is a program that can run on many different operating systems and which has operating-system specific components -- these would be the "subsystems".
However, creating an application in this way does sound like the kind of thing that was done fifteen or twenty years ago. That's about the time that people used to refer to those three families of operating systems, too...