shared-memory

The details of the MESI protocol for multicore processors would be really important for me, but I can't find them anywhere. Even http://www.intel.com/content/dam/doc/manual/64-ia-32-architectures-software-developer-vol-3a-part-1-manual.pdf doesn't contain enough detail. For instance: assume a private L1 and shared L2 cache. If the state of a line is exclusive in L1, then is it exclusive in L2 too (or invalid, because only in one cache could be the state of a line exclusive)? And clearly, if another core writes this line, the state of the previously exclusive line in L1 becomes invalid, but how

I have 64-bit Linux machine(Intel Xeon L5410 @ 2.33GHz). **meminfo:** MemTotal: 24672736 kB MemFree: 145372 kB Buffers: 181896 kB Cached: 22004648 kB SwapCached: 195072 kB Active: 9761028 kB Inactive: 13964532 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 24672736 kB LowFree: 145372 kB SwapTotal: 17414452 kB SwapFree: 15618852 kB Dirty: 2125148 kB Writeback: 0 kB AnonPages: 1358396 kB Mapped: 1069632 kB Slab: 699464 kB CommitLimit: 29750820 kB Committed_AS: 9236252 kB PageTables: 38620 kB VmallocTotal: 34359738367 kB VmallocUsed: 17272 kB VmallocChunk: 34359718843 kB HugePages_Total: 0 HugePages

The cluster that I work with recently switched from SGE to SLURM. I was wondering what the difference between sbatch options --ntasks and --cpus-per-task ? --ntasks seemed appropriate for some MPI jobs that I ran but did not seem appropriate for some OpenMP jobs that I ran. For the OpenMP jobs in my SLURM script, I specified: #SBATCH --ntasks=20 All the nodes in the partition are 20core machines, so only 1 job should run per machine. However, multiple jobs were running simultaneously on each node. Tasks in SLURM are basically processes / mpi ranks - it seems you just want a single task. A task

In short, my question is: If you have class, MyClass<T> , how can you change the class definition to support cases where you have MyClass<T, Alloc> , similar to how, say, STL vector provides. I need this functionality to support an allocator for shared memory. Specifically, I am trying to implement a ring buffer in shared memory. Currently it has the following ctor: template<typename ItemType> SharedMemoryBuffer<ItemType>::SharedMemoryBuffer( unsigned long capacity, std::string name ) where ItemType is the type of the data to be placed in each slot of the buffer. Now, this works splendid when

I'm using boost 1.53 and GCC 4.1.2 . I've tried to use boost unordered_map in some tests (documentation says, that it should work with shared memory), but i'm unable to compile my code. With interprocess::map instead of unordered everything is ok. Typedefs: typedef boost::interprocess::allocator<char, SegmentManager> CharAllocator; typedef boost::interprocess::basic_string<char, std::char_traits<char>, CharAllocator> ShmString; typedef ShmString HashKeyType; //ComplexType is a wrapper for internal interprocess::map typedef ComplexType HashMappedType; typedef std::pair<const ShmString,

When I do this : myProgram.h myProgram.c struct PipeShm { // all my fields // more // ... }; struct PipeShm myPipe = { /* initialization for all fields */ }; struct PipeShm * sharedPipe = &myPipe; void func() { sharedPipe = mmap (NULL, sizeof * sharedPipe, PROT_READ | PROT_WRITE,MAP_SHARED | MAP_ANONYMOUS, -1, 0); } When I mmap the pointer sharedPipe , if I invoke from main() any methods from myProgram code, would all processes share the exact shared memory that I shared with myPipe struct? Or would each new child that's created, would have a new myPipe of his own? Regards EDIT: This is after

Here is a program foo.c that writes data to shared memory. #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <stdint.h> #include <unistd.h> #include <sys/ipc.h> #include <sys/shm.h> int main() { key_t key; int shmid; char *mem; if ((key = ftok("ftok", 0)) == -1) { perror("ftok"); return 1; } if ((shmid = shmget(key, 100, 0600 | IPC_CREAT)) == -1) { perror("shmget"); return 1; } printf("key: 0x%x; shmid: %d\n", key, shmid); if ((mem = shmat(shmid, NULL, 0)) == (void *) -1) { perror("shmat"); return 1; } sprintf(mem, "hello"); sleep(10); sprintf(mem, "exit");