Throttling at will the execution and display speed of a particular process, for example, a game, a flash game, or an OpenGL game. I want to be able to slow it down to 20% or 0.5%. This is simply not possible on host space in linux.
But linux supports two kernel-level virtualisation environments: KVM and lxc.
Question: Is it possible to provide a fake system clock to a virtual lxc or KVM machine so that a flash game running in the guest will not run faster than what is set to run?
Some choices:
Qemu brake patch (will require work to apply no doubt.)
Bochs has ips=NNNN to define CPU "Instructions Per Second".
cpulimit a tool for limiting the CPU usage of a process (does not require virtualization.)
Update: You want this: https://superuser.com/questions/454534/how-can-i-slow-down-the-framerate-of-a-flash-game
I found a prototype version of the CheatEngine speed hack that works for linux.
http://forum.cheatengine.org/viewtopic.php?t=533437&sid=1a83d81ee08f8479eb8b190939b2e1aa
http://code.google.com/p/xeat-engine/source/checkout
http://pastebin.com/ZLryd20D
Basically it replaces gettimeofday with a hacked version using LD_PRELOAD magic. It works perfectly!
thanks lilezek! wherever you are!
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I am facing a design "issue". I have a board with Xilinx Zynq Soc including dual-core ARM9 and I need to develop an application to support real-time property control application (time deadlines to response time) and also application to do heavy processing (image etc.) and some basic communications between them, but most importantly I will need to be able to control the Linux part (at least e.g. to somehow suspend it, "pause it" in best case to have possibility to shut it down and then run it again). So I was wondering how to combine it.
One of the option, could be RTLinux, which at least to description, what I found offers possibility to run realtime kernel and linux kernel next to it as a thread but it seems that it is now proprieatary by WindRiver..
Then I stepped up over MicroBlaze, where it could be possible to "create" soft processor on Programmable logic, but I am not sure if I can run RTOS on ARM and Linux there?
There are two things that seem to be known as rtlinux. The one you mention, a Wind River revival of the MERT system is a product of that company. Another one, seemingly “RT Linux”, is a real time patch to the mainline kernel which provides deterministic scheduling and fine grained kernel pre-emption.
I think it is the latter one that you want. 10s of google indicates that there is a kconfig target for this SoC, so all the pieces you need should be there.
Do remember there is more to a real time system than just the ability to be real time; the subsystems also have to be well behaved.
Given your description, you have (at least) the following design options:
Dual kernel approach: this means patching the Linux kernel with a (quite invasive) patch that runs a tiny real-time kernel alongside the standard kernel. This approach allows reaching good real-time performance (even in the order of us) at the cost of complexity. It was implemented by the RTLinux project (acquired and then discontinued by Windriver), then by RTAI (mostly focusing on x86) and Xenomai.
If you go along this path, you can see if Xenomai supports your specific SoC; then patch, configure and rebuild the kernel; and finally write the real-time code following Xenomai's API.
Improving the responsiveness of the Linux standard kernel: this is what the PREEMPT_RT project aims at. The real-time performance is lower with respect to the previous approach, but you don't have to write real-time specific code. With this approach, you can patch and build the kernel, then see if the real-time performance is sufficient for your needs.
Synthesizing a Microblaze soft-core on the FPGA, then run Linux on the ARM cores and the real-time code ((either bare-metal or with an RTOS) on the Microblaze.
Unfortunately, your specific SoC does not support ARM's virtualization extensions. Otherwise there would be the additional option of Multi-OS approach: running the Linux OS on one ARM core and the real-time code (either bare-metal or with an RTOS like ERIKA Enterprise) on the other ARM core, through a hypervisor like Jailhouse or Xen.
I really like the idea of running, optimizing my software on old hardware, because you can viscerally feel when things are slower (or faster!). The most obvious way to do this is to buy an old system and literally use it for development, but that would allow down my IDE, and compiler and all other development tasks, which is less helpful, and (possibly) unnecessary.
I want to be able to:
Run my application at various levels of performance, on demand
At the same time, run my IDE, debugger, compiler at full speed
On a single system
Nice to have:
Simulate real, specific old systems, with some accuracy
Similarly throttle memory speed, and size
Optionally run my build system slowly
Try use QEMU in full emulation mode, but keep in mind it's use more cpu resources.
https://stuff.mit.edu/afs/sipb/project/phone-project/OldFiles/share/doc/qemu/qemu-doc.html
QEMU has two operating modes:
Full system emulation. In this mode, QEMU emulates a full system (for example a PC), including one or several processors and various peripherals. It can be used to launch different Operating Systems without rebooting the PC or to debug system code.
User mode emulation (Linux host only). In this mode, QEMU can launch Linux processes compiled for one CPU on another CPU.
Possible architectures can see there:
https://wiki.qemu.org/Documentation/Platforms
I was checking project Embedded ECG data acquisition system from instructables and there is mension a TODO:
Combining the OS and bare-bone firmware
UNDER CONSTRUCTION
** Since the bootloader only loads one firmware to the Core,
I need to modify the ELF file, to have Linux and bare-bone Core at the same time **
It seems to me as interresting approach how to make full featured Linux and critical realtime OS on one board (for example Raspberry PI). It is really possible? I have heard, that Linux can be setup to not use some cores. But I suppose that Linux use virtual memory and bare-bone firmware does usually not. Can the memory be shared between these OS. What about interruptions? Can these two OS handle interruptions separately? Can boot loader load these two systems to both core at once? I can imagine that one thread in boot loader will skip to address of bare-bone OS. It is correct approach?
Yes, it is possible, even if the full setup is not straightforward.
A couple of examples:
Xilinx released a white paper explaining how to run Linux + FreeRTOS on a dual-core Zynq ARM
Evidence explained how to run Linux + Erika Enterprise RTOS on a dual-core Freescale imx6 ARM
Those examples are based on system partitioning by hard-coding the assignment of the different cores to different OSs.
If your system is capable of hardware-assisted virtualization, you can use an hypervisor for making (and enforcing) such partitioning. You can for example use Siemen's Jailhouse, KVM or Xen.
Kind of. This is what people already do to some extent with network stack / driver. For example IsoStack idea works in a similar way. There's a project which actually implements this on linux by dedicating cores to network cards, but my google-fu is failing me.
i am trying to measure code performance (basically speed-up when using threads). So far i was using cygwin via windows or linux on separate machine. Now i have the ability to set up a new system and i am not sure whether i should have dual boot (windows and ubuntu) or a virtual machine.
My concern is whether i can measure reliable speed up and possibly other stuff (performance monitors) via a linux virtual machine or if i have to go with with normal booting in linux.
anybody have an opinion?
If your "threading" relies heavily on scheduling, I won't recommend you to use VM. VM is just a normal process from the host OS's point of view, so the guest kernel and its scheduler will be affected by scheduling by the host kernel.
If your "threading" is more like parallel computation, I think it's OK to use VM.
For me, it is much safer to boot directly on the system and avoid using a VM in your case. Even when you don't use a VM, it is already hard to have twice the same results in multi-threading because the system being used for OS tasks, so having 2 OS running in the same time as for VM even increases the uncertainty on the results. For instance, running your tests 1000 times on a VM would lead to, let's say, 100 over-estimated time, while it would maybe be only 60 on a lonely OS. It is your call to know if this uncertainty is acceptable or not.
I want to determine if my application is IO or CPU bounded. Is there such a tool to determine how much of your application's run time is spent on CPU wait/IO wait/running on CPU etc.?
I am running my application from terminal.
I have heard there is such a tool for linux actually but I don't what is it.
You can use a combination of mpstat and iostat (I don't believe the former is available for OS X).
Here is a list of the top 5 monitoring tools for ubuntu. You can collect quite a bit of info.
I think you can try the nmon.It can be used in most Linux environment.