RE: Pth Scheduling Policy
I have some doubts regarding the way in which the Pth scheduler implements Priority based non-preemptive Scheduling. When a low-priority thread make a higher-priority thread ready-to-run, it is offering the CPU to that higher-priority thread. My program is using the pth cond and mutex variables for synchronization between the threads. From a low priority thread, I am calling pth_cond_notify() and immediately a higher priority thread (which was there in the ready queue) was getting scheduled. Well, that's the purpose of 'pth_cond_notify'. It is, after all, a synchronization function. I analyzed the pth_cond_notify () and saw a pth_yield() inside that function. This pth_yield() is preempting the lower priority thread that called the pth_cond_notify(). It's not preempting it, the lower priority thread explicity made the higher priority thread ready-to-run by calling a synchronization function. But my application was expecting a pure non-preemptive response. You weren't pre-empted, you made a higher-priority thread run. Can I achieve the non-preemptive response if I remove the pth_yield() in pth_cond_notify() ? Will there be any performance issue with the Pth library, if I remove the pth_yield () in pth_cond_notify() ? It's hard for me to imagine why you would want to do this. What's the point of having thread priorities if you want to keep the higher-priority threads from running? But, yes, it should be safe and should do what you want. But I think it's quite likely that you're doing something fundamentally odd, possibly poorly thought out, that makes you want this. DS __ GNU Portable Threads (Pth)http://www.gnu.org/software/pth/ Development Site http://www.ossp.org/pkg/lib/pth/ Distribution Files ftp://ftp.gnu.org/gnu/pth/ Distribution Snapshots ftp://ftp.ossp.org/pkg/lib/pth/ User Support Mailing List[EMAIL PROTECTED] Automated List Manager (Majordomo) [EMAIL PROTECTED]
RE: Pth Scheduling Policy
My program is using the pth cond and mutex variables for synchronization between the threads. From a low priority thread, I am calling pth_cond_notify() and immediately a higher priority thread (which was there in the ready queue) was getting scheduled. Well, that's the purpose of 'pth_cond_notify'. It is, after all, a synchronization function. I think in a non preemptive system, the library cannot force the application to yield the CPU unless the application by itself does an yield. Using pth_cond_notify, a thread just wants to notify another thread that, an event has occurred and it doesn't mean that it should also relinquish the CPU. Its upto that thread whether to continue with the processing or not. Is there any other call in Pth which can be used for sending a notification to a thread, without relinquishing the CPU ? Regards, Vinu - Disclaimer - This message(including attachment if any)is confidential and may be privileged.Before opening attachments please check them for viruses and defects.MindTree Consulting Private Limited (MindTree)will not be responsible for any viruses or defects or any forwarded attachments emanating either from within MindTree or outside.If you have received this message by mistake please notify the sender by return e-mail and delete this message from your system. Any unauthorized use or dissemination of this message in whole or in part is strictly prohibited. Please note that e-mails are susceptible to change and MindTree shall not be liable for any improper, untimely or incomplete transmission. -
RE: Pth Scheduling Policy
My program is using the pth cond and mutex variables for synchronization between the threads. From a low priority thread, I am calling pth_cond_notify() and immediately a higher priority thread (which was there in the ready queue) was getting scheduled. Well, that's the purpose of 'pth_cond_notify'. It is, after all, a synchronization function. I think in a non preemptive system, the library cannot force the application to yield the CPU unless the application by itself does an yield. I think a non-preemptive system should be as much like a pre-emptive system as possible. Is there any other call in Pth which can be used for sending a notification to a thread, without relinquishing the CPU ? Yes, just set your priority to the highest priority until you're ready to let another thread run. DS __ GNU Portable Threads (Pth)http://www.gnu.org/software/pth/ Development Site http://www.ossp.org/pkg/lib/pth/ Distribution Files ftp://ftp.gnu.org/gnu/pth/ Distribution Snapshots ftp://ftp.ossp.org/pkg/lib/pth/ User Support Mailing List[EMAIL PROTECTED] Automated List Manager (Majordomo) [EMAIL PROTECTED]
