find the pages accessed by thread

I am looking for some scheduling options based on data accessed by threads. Is there any way to find the pages of cache accessed by a specific thread. If i have two threads from two different processes, is it possible to find the common data/pages accessed by both the threads

Two threads from the same process are potentially sharing the whole process memory space. If the programme does not restrict access to certain regions of memory to the threads, it might be difficult to know exactly which thread should be assigned to which cpu.

For more threads, the problem becomes more difficult, as a thread may share different data with several different threads, and create a network of relationship. If a relation between two threads mandates their affinity to a given cpu core, by transitivity all the threads of their relationship network should be bound to that very same core as well. Perhaps the number of relations, or some form of clustering analysis (biconnectivity) would help.

Regarding your specific question, if two threads are sharing data, but are from different processes, then these processes are necessarily sharing these pages voluntarily by using shm_open (to create a shared memory segment) and mmap (to map that segment in the process memory). It is not possible to share data pages between processes otherwise, excepted implicitely (again) with the copy on write mechanism used by the OS for forked processes, in which case each page remains shared until one process makes a write to it.

The explicit sharing of pages (by shm_open) may be used to programmatically define the same CPU affinity for both threads - perhaps by convention in both programs to associate the relevant threads with the first core, or through a small handshaking protocol established at some point through the shared memory object (for instance the first byte of the memory segment could be set to the chosen cpu number + 1 by the first thread to access it, 0 meaning no affinity yet).

Unfortunately, the posix thread API doesn't provide a way to set cpu affinity for threads. You may use the non portable extension provided on the linux platform pthread_attr_setaffinity_np, with the cpuset family of functions to configure a thread affinity.

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