context-switch

There's an example in Maurice Bach's The Design of the Unix Operating System that mentions how it's possible for a doubly linked list to be destroyed due to a context switch during its creation. (He goes on to say that this is prevented by raising the processor level during such critical regions of code, but I'm having trouble understanding his reasoning that tries to show the problem in the first place) The sample code that he includes is as follows: struct queue { } *bp, *bp1; bp1 -> forp = bp -> forp; bp1 -> backp = bp; bp -> forp = bp1; /* consider possible context switch here */ bp1 ->

Out of curiosity I want to know how many times my program was context switched by the OS. Like all the registers were saved and the control was passed to another process or thread, and then after some time everything was restored and we continue as it never happened. Does the system maintain such a number somewhere or is there a sort of hack or whatever? I am on Linux in particular but I am interested about other systems as well. Well, let's examine the case. Linux type O/S keeps these details systematically and one may use a comfort of python, for both inspecting the state and also for easy

I am investigating how run a process on a dedicated CPU in order to avoid context-switches. On my Ubuntu, I isolated two CPUs using the kernel parameters "isolcpus=3,7" and "irqaffinity=0-2,4-6". I am sure that it is correctly taken into account: $ cat /proc/cmdline BOOT_IMAGE=/boot/vmlinuz-4.8.0-27-generic root=UUID=58c66f12-0588-442b-9bb8-1d2dd833efe2 ro quiet splash isolcpus=3,7 irqaffinity=0-2,4-6 vt.handoff=7 After a reboot, I can check that everything works as expected. On a first console I run $ stress -c 24 stress: info: [31717] dispatching hogs: 24 cpu, 0 io, 0 vm, 0 hdd And on a

I normally append an encoded json object to the response body, however I now have a situation that warrants using the ContextSwitch action helper. I have a Zend_Form that requires three different response contexts: html - Render the form as normal html within a layout. html-partial - An ajax "get" request that renders just the form as html. json - An ajax "post" request that returns any form valiation error messages. For each context I have 3 view scripts. Although the two html contexts could use the same view script, but I haven't figured out if this is possible. form.phtml form.html.phtml

Is there any good empirical data on the cost of context switching between threads of the same process on Linux (x86 and x86_64, mainly, are of interest)? I'm talking about the number of cycles or nanoseconds between the last instruction one thread executes in userspace before getting put to sleep voluntarily or involuntarily, and the first instruction a different thread of the same process executes after waking up on the same cpu/core. I wrote a quick test program that constantly performs rdtsc in 2 threads assigned to the same cpu/core, stores the result in a volatile variable, and compares

I would like to monitor the the context switching behavior in a multi-threaded pthread application. In other RTOSes(Micro C OS) I have been able to register a context switch callback for each thread in the application, and then log (or toggle a gpio) and watch the thread context switching in real time. This was a valuable tool for debugging the real time behavior and interaction of the multiple threads. My current environment is embedded linux utilizing the pthread api. Is there a way to monitor each of the context switches? Not in the way you describe, however there are various profiling

I'm trying to understand how the schedule process in linux kernel actually works. My question is not about the scheduling algorithm. Its about how the functions schedule() and switch_to() work. I'll try to explain. I saw that: When a process runs out of time-slice, the flag need_resched is set by scheduler_tick() . The kernel checks the flag, sees that it is set, and calls schedule() (pertinent to question 1) to switch to a new process. This flag is a message that schedule should be invoked as soon as possible because another process deserves to run. Upon returning to user-space or returning

Can we write a c program to find out time spent in context switch in Linux? Could you please share code if you have one? Thanks Profiling the switching time is very difficult, but the in-kernel latency profiling tools, as well as oprofile (which can profile the kernel itself) will help you there. For benchmarking the interactive application performance, I have written a small tool called latencybench that measures unexpected latency spikes: // Compile with g++ latencybench.cc -o latencybench -lboost_thread-mt // Should also work on MSVC and other platforms supported by Boost. #include <boost