1 / 49

Portable Operating System Interface Thread

Portable Operating System Interface Thread. Yukai Hung a0934147@gmail.com Department of Mathematics National Taiwan University. POSIX Thread Basic. POSIX Thread Basic. What is process? What is thread? - a thread of execution is the smallest unit of processing that can be

ivory
Download Presentation

Portable Operating System Interface Thread

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Portable Operating System Interface Thread YukaiHung a0934147@gmail.comDepartment of MathematicsNational Taiwan University

  2. POSIX Thread Basic

  3. POSIX Thread Basic • What is process? What is thread? • - a thread of execution is the smallest unit of processing that can be • scheduled by operating system, which is contained inside a process • - multiple threads can exist within the same process and share • resources, while different processes do not share the resources • How to create new process? • - use system function fork(), which creates a copy of itself • - parent and child process can tell each other apart by examining • the return value of fork() system function (non-zero or zero value) 3

  4. POSIX Thread Basic • int pthread_create(…) • create new thread with specified thread attributes and • execute thread function with specified function arguments • http://opengroup.org/onlinepubs/007908799/xsh/pthread_create.html • void pthread_exit(…) • terminate the current calling thread and makes the return value • pointer available to any successful join with the terminating thread • http://opengroup.org/onlinepubs/007908799/xsh/pthread_exit.html • int pthread_join(…) • suspend the execution of the current calling thread or process until the • target thread terminates, unless the target thread has already terminated • http://opengroup.org/onlinepubs/007908799/xsh/pthread_join.html 4

  5. POSIX Thread Basic #include <stdio.h> #include <stdlib.h> #include <pthread.h> • int main(int argc,char** argv) • { • int error1; • int error2; • int input1; • int input2; • int return1; • int return2; • pthread_tthread1; • pthread_tthread2; • input1=1; • input2=2; • error1=pthread_create(&thread1,NULL,tfunction,(void*)&input1); • error2=pthread_create(&thread2,NULL,tfunction,(void*)&input2); 5

  6. POSIX Thread Basic • if(error1!=0||error2!=0) • printf(“Error:thread create\n”); • error1=pthread_join(thread1,(void*)&return1); • error2=pthread_join(thread2,(void*)&return2); • if(error1!=0||error2!=0) • printf(“Error:thread join\n”); • printf(“thread 1 return %d\n”,return1)); • printf(“thread 2 return %d\n”,return2)); • return 0; • } 6

  7. POSIX Thread Basic • void* tfunction(void* input) • { • printf(“thread %d is executing\n”,*((int*)input)); • pthread_exit((void*)1); • } 7

  8. POSIX Thread Basic • int pthread_equal(…) • compare two threads from two thread handles • http://opengroup.org/onlinepubs/007908799/xsh/pthread_equal.html • pthread_tpthread_self(…) • return the thread handle of the current calling thread • http://opengroup.org/onlinepubs/007908775/xsh/pthread_self.html • int pthread_cancel(…) • request the thread be canceled, the target threads cancelability • states and types determines when the cancellation takes effects • http://opengroup.org/onlinepubs/007908775/xsh/pthread_cancel.html 8

  9. POSIX Thread Basic • void pthread_cleanup_push(…) • the function shall push the specified cancellation cleanup handler • handler routine onto the calling threads cancellation cleanup stack • http://linux.die.net/man/3/pthread_cleanup_push • void pthread_cleanup_pop(…) • the function shall remove the routine at the top of calling cleanup • thread cancellation stack and optionally invoke it (if input is non-zero) • http://linux.die.net/man/3/pthread_cleanup_pop 9

  10. POSIX Thread Basic #include <stdio.h> #include <stdlib.h> #include <pthread.h> • int main(int argc,char** argv) • { • int rvalue; • pthread_tthread; • if(pthread_create(&thread,NULL,tfunction,(void*)1)!=0) • printf(“Error:thread create\n”); • if(pthread_join(thread,(void*)&rvalue)!=0) • printf(“Error:thread join\n”); • printf(“thread return %d\n”,rvalue)); • return 0; • } 10

  11. POSIX Thread Basic void* tfunction(void* input) { printf(“thread start\n”); • pthread_cleanup_push(cleanup,"thread first handler"); • pthread_cleanup_push(cleanup,"thread second handler"); • printf("thread push complete\n"); • pthread_cleanup_pop(1); • pthread_cleanup_pop(1); • return (void*)1; } • void cleanup(void* string) • { • printf(“cleanup:%s\n”,(char*)string); • return; • } 11

  12. Race Condition and Mutex Lock

  13. Race Condition and Mutex Lock • Consider the following parallel program • - threads are almost impossibly executed at the same time 13

  14. Race Condition and Mutex Lock • Scenario 1 • - the result value R is 2 if the initial value R is 1 14

  15. Race Condition and Mutex Lock • Scenario 2 • - the result value R is 2 if the initial value R is 1 15

  16. Race Condition and Mutex Lock • Scenario 3 • - the result value R is 3 if the initial value R is 1 16

  17. Race Condition and Mutex Lock • Solve the race condition by Locking • - manage the shared resource between threads • - avoid the deadlock or unbalanced problems 17

  18. Race Condition and Mutex Lock • Guarantee the executed instruction order is correct • - the problem is back to the sequential procedure • - lock and release procedure have high overhead 18

  19. Race Condition and Mutex Lock • Solve the race condition by Semaphore • - multi-value locking method (binary locking extension) • - instructions in procedure P and V are atomic operations 19

  20. Race Condition and Mutex Lock #include <stdio.h> #include <stdlib.h> #include <pthread.h> • int main(int argc,char** argv) • { • int value; • int error1; • int error2; • pthread_tthread1; • pthread_tthread2; • value=0; • error1=pthread_create(&thread1,NULL,tfunction,(void*)&value); • error2=pthread_create(&thread2,NULL,tfunction,(void*)&value); • if(error1!=0||error2!=0) • printf(“Error:thread create\n”); 20

  21. Race Condition and Mutex Lock • error1=pthread_join(thread1,NULL); • error2=pthread_join(thread2,NULL); • if(error1!=0||error2!=0) • printf(“Error:thread join\n”); • printf(“final result is %d\n”,value)); • return 0; • } • void* tfunction(void* input) • { • *((int*)input)=*((int*)input)+1; • return NULL; • } 21

  22. Race Condition and Mutex Lock • int pthread_mutex_init(…) • initialize the mutex referenced by mutex with specified attributes • initialize an already initialized mutex results in undefined behavior • http://opengroup.org/onlinepubs/007908775/xsh/pthread_mutex_init.html • int pthread_mutex_destroy(…) • destroy the previously initialized mutex lock • the mutex must not be used after it has been destroyed • http://www.mkssoftware.com/docs/man3/pthread_mutex_destroy.3.asp 22

  23. Race Condition and Mutex Lock • int pthread_mutex_lock(…) • lock the specified initialized mutex. if the mutex is already locked, • the calling thread blocks until he mutex becomes available or unlock • http://www.mkssoftware.com/docs/man3/pthread_mutex_lock.3.asp • int pthread_mutex_unlock(…) • attempt to unlock the specified mutex. If there are threads blocked on the mutex • object when unlock function is calling, resulting in the mutex becoming available • the scheduling policy is used to determine which thread acquire the mutex • http://www.mkssoftware.com/docs/man3/pthread_mutex_unlock.3.asp • int pthread_mutex_trylock(…) • try to lock the specified mutex. If the mutex is already locked, an error is • returned, otherwise, the operation returns with the mutex in the locked • state with the calling thread as its owner • http://www.mkssoftware.com/docs/man3/pthread_mutex_trylock.3.asp 23

  24. Race Condition and Mutex Lock #include <stdio.h> #include <stdlib.h> #include <pthread.h> • pthread_mutex_twork_mutex; • int main(int argc,char** argv) • { • int value; • int error1; • int error2; • pthread_tthread1; • pthread_tthread2; • value=0; • if(pthread_mutex_init(&work_mutex,NULL)!=0) • printf(“Error:work mutex create\n”); 24

  25. Race Condition and Mutex Lock • error1=pthread_create(&thread1,NULL,tfunction,(void*)&value); • error2=pthread_create(&thread2,NULL,tfunction,(void*)&value); • if(error1!=0||error2!=0) • printf(“Error:thread create\n”); • error1=pthread_join(thread1,NULL); • error2=pthread_join(thread2,NULL); • if(error1!=0||error2!=0) • printf(“Error:thread join\n”); • printf(“final result is %d\n”,value); • if(pthread_mutex_destroy(&work_mutex)!=0) • printf(“Error:work mutex destroy\n”); • return 0; • } 25

  26. Race Condition and Mutex Lock • void* tfunction(void* input) • { • int* value; • if(pthread_mutex_lock(&work_mutex)!=0) • printf(“Error:lock work mutex\n”); • *((int*)input)=*((int*)input)+1; • if(pthread_mutex_unlock(&work_mutex)!=0) • printf(“Error:work mutex unlock\n”); • return NULL; • } 26

  27. Signal and Condition Variable

  28. Signal and Condition Variable • int pthread_cond_init(…) • initialize the condition variable referenced by cond with specified attributes • initialize an already initialized condition variable results in undefined behavior • http://opengroup.org/onlinepubs/007908775/xsh/pthread_cond_init.html • int pthread_cond_destroy(…) • destroy the previously initialized condition variable • the condition variable must not be used after it has been destroyed 28

  29. Signal and Condition Variable • int loop=1; • pthread_cond_tcond; • pthread_mutex_tmutex; • int main(int argc,char** argv) • { • pthread_tthread1; • pthread_tthread2; • pthread_cond_init(&cond,NULL); • pthread_mutex_init(&mutex,NULL); • pthread_create(&thread1,NULL,fthread1,(void *)NULL); • pthread_create(&thread2,NULL,fthread2,(void *)NULL); • pthread_join(thread1,NULL); • pthread_join(thread2,NULL); • pthread_cond_destroy(&cond); • pthread_mutex_destroy(&mutex); • return 0; • } 29

  30. Signal and Condition Variable void* fthread1(void* input) { for(loop=1;loop<=9;loop++) { pthread_mutex_lock(&mutex); if(loop%3==0) pthread_cond_signal(&cond); else printf("thread1:%d\n",loop); pthread_mutex_unlock(&mutex); sleep(1); } return NULL; }; 30

  31. Signal and Condition Variable void* fthread2(void* input) { while(loop<9) { pthread_mutex_lock(&mutex); if(loop%3!=0) pthread_cond_wait(&cond,&mutex); printf("thread2:%d\n",loop); pthread_mutex_unlock(&mutex); sleep(1); } return NULL; }; 31

  32. Multiple Thread and Multiple GPU

  33. Multiple Thread and Multiple GPU • A host thread can maintain one context at a time • - need as many host threads as GPUs to maintain all device • - multiple host threads can establish context with the same GPU • hardware diver handles time-sharing and resource partitioning device 0 device 1 device 2 host thread 0 host thread 1 host thread 2 host memory 33

  34. Multiple Thread and Multiple GPU • cudaGetDeviceCount() • returns the number of devices on the current system with compute, • capability greater or equal to 1.0, that are available for execution • cudaSetDevice() • set the specific device on which the active host thread executes the • device code. If the host thread has already initialized he cuda runtime • by calling non-device management runtime functions, returns error • must be called prior to context creation, fails if the context has already • been established, one can forces the context creation with cudaFree(0) • cudaGetDevice(…) • returns the device on which the active host thread executes the code 34

  35. Multiple Thread and Multiple GPU #include <cuda.h> #include <stdio.h> #include <stdlib.h> #include <pthread.h> • #define MaxDevice 8 • int main(int argc,char** argv) • { • int size; • int loop; • int devicecount; • float* h_veca; • float* h_vecb; • float* h_vecc; • pthread_tthreadt[MaxDevice]; • pthread_cthreadc[MaxDevice]; • size=32000*4; • h_veca=(float*)malloc(sizeof(float)*size); • h_vecb=(float*)malloc(sizeof(float)*size); • h_vecc=(float*)malloc(sizeof(float)*size); 35

  36. Multiple Thread and Multiple GPU • for(loop=0;loop<size;loop++) • { • h_veca[loop]=1.0f; • h_vecb[loop]=2.0f; • h_vecc[loop]=0.0f; • } • cudaGetDeviceCount(&devicecount); • devicecount=(devicecount>MaxDevice)?MaxDevice:devicecount; • printf(“device number is %d\n”,devicecount); • for(loop=0;loop<devicecount;loop++) • { • threadc[loop].index=loop; • threadc[loop].subsz=size/devicecount; • threadc[loop].hveca=h_veca+loop*subsz; • threadc[loop].hvecb=h_vecb+loop*subsz; • threadc[loop].hvecc=h_vecc+loop*subsz; • } • for(loop=0;loop<devicecount;loop++) • pthread_create(threadt+loop,NULL,tfunction,(void*)(threadc+loop)); 36

  37. Multiple Thread and Multiple GPU • for(loop=0;loop<devicecount;loop++) • pthread_join(threadt[loop],NULL); • for(loop=0;loop<size;loop++) • if(h_vecc[loop]!=3.0f) • printf(“Error:check result\n”); • free(h_veca); • free(h_vecb); • free(h_vecc); • return 0; • }; • structpthread_c • { • int index; • int subsz; • float* hveca; • float* hvecb; • float* hvecc; • }; 37

  38. Multiple Thread and Multiple GPU • void* tfunction(void* content) • { • int index; • int subsz; • int gsize; • int bsize; • float *hveca,*dveca; • float *hvecb,*dvecb; • float *hvecc,*dvecc; • index=(*((pthread_c*)content)).index; • subsz=(*((pthread_c*)content)).subsz; • hveca=(*((pthread_c*)content)).hveca; • hvecb=(*((pthread_c*)content)).hvecb; • hvecc=(*((pthread_c*)content)).hvecc; • printf(“thread %d start!\n”,index); • //for(int loop=0;loop<subsz;loop++) • //hvecc[loop]=hveca[loop]+hvecb[loop]; • cudaSetDevice(index); 38

  39. Multiple Thread and Multiple GPU • cudaMalloc((void**)&dveca,sizeof(float)*subsz); • cudaMalloc((void**)&dvecb,sizeof(float)*subsz); • cudaMalloc((void**)&dvecc,sizeof(float)*subsz); • cudaMemcpy(dveca,hveca,sizeof(float)*subsz,cudaMemcpyHostToDevice); • cudaMemcpy(dvecb,hvecb,sizeof(float)*subsz,cudaMemcpyHostToDevice); • bsize=256; • gsize=(int)ceil((float)subsz/256); • vecAdd<<<gsize,bsize>>>(dveca,dvecb,dvecc,subsz); • cudaMemcpy(hvecc,dvecc,sizeof(float)*subsz,cudaMemcpyDeviceToHost); • cudaFree(dveca); • cudaFree(dvecb); • cudaFree(dvecc); • cudaError_t error; • if((error=cudaGetLastError())!=cudaSuccess) • printf(“cudaError:%s\n”,cudaGetErrorString(error)); • printf(“thread %d finish!\n”,index); • return NULL; • }; 39

  40. Multiple Thread and Multiple GPU • __global__ void vecAdd(float* veca,float* vecb,float* vecc,int size) • { • int index; • index=blockIdx.x*blockDim.x+threadIdx.x; • if(index<size) • vecc[index]=veca[index]+vecb[index]; • return; • }; 40

  41. Multiple Thread and Multiple GPU • Where is constant memory? • - data is stored in the device global memory • - read data through multiprocessor constant cache • - 64KB constant memory and 8KB cache for each multiprocessor • How about the performance? • - optimized when warp of threads read same location • - 4 bytes per cycle through broadcasting to warp of threads • - serialized when warp of threads read in different location • - very slow when cache miss (read data from global memory) • - access latency can range from one to hundreds clock cycles 41

  42. Multiple Thread and Multiple GPU • How to use constant memory? • - declare constant memory on the file scope (global variable) • - copy data to constant memory by host (because it is constant!!) //declare constant memory __constant__ float cst_ptr[size]; //copy data from host to constant memory • cudaMemcpyToSymbol(cst_ptr,host_ptr,data_size); 42

  43. Multiple Thread and Multiple GPU //declare constant memory __constant__ float cangle[360]; int main(int argc,char** argv) { int size=3200; float* darray; • float hangle[360]; //allocate device memory cudaMalloc((void**)&darray,sizeof(float)*size); //initialize allocated memory cudaMemset(darray,0,sizeof(float)*size); //initialize angle array on host for(int loop=0;loop<360;loop++) hangle[loop]=acos(-1.0f)*loop/180.0f; //copy host angle data to constant memory cudaMemcpyToSymbol(cangle,hangle,sizeof(float)*360); 43

  44. Constant Memory //execute device kernel test_kernel<<<size/64,64>>>(darray); //free device memory cudaFree(darray); return 0; } __global__ void test_kernel(float* darray) { int index; //calculate each thread global index index=blockIdx.x*blockDim.x+threadIdx.x; #pragma unroll 10 for(int loop=0;loop<360;loop++) darray[index]=darray[index]+cangle[loop]; return; }; 44

  45. Multiple Thread and Multiple GPU #include <cuda.h> #include <stdio.h> #include <stdlib.h> #include <pthread.h> • #define MaxDevice 8 • __constant__ float cangle[360]; • int main(int argc,char** argv) • { • int loop; • int devicecount; • float summation; • float hangle[360]; • pthread_tthreadt[MaxDevice]; • pthread_cthreadc[MaxDevice]; • for(loop=0;loop<360;loop++) • hangle[loop]=acos(-1.0f)*loop/180.0f; • for(loop=0,summation=0.0f;loop<360;loop++) • summation=summation+hangle[loop]; 45

  46. Multiple Thread and Multiple GPU • cudaGetDeviceCount(&devicecount); • devicecount=(devicecount>MaxDevice)?MaxDevice:devicecount; • for(loop=0;loop<devicecount;loop++) • { • threadc[loop].index=loop; • threadc[loop].hangle=hangle; • threadc[loop].summation=summation; • } • for(loop=0;loop<devicecount;loop++) • pthread_create(threadt+loop,NULL,tfunction,(void*)(threadc+loop)); • for(loop=0;loop<devicecount;loop++) • pthread_join(threadt[loop],NULL); • return 0; • } • structpthread_c • { • int index; • float* hangle; • float summation; • }; 46

  47. Multiple Thread and Multiple GPU • void* tfunction(void* content) • { • int size; • int index; • int gsize; • int bsize; • float summation; • float* hangle; • float* hvector; • float* dvector; • size=32000; • index=(*((pthread_c*)content)).index; • hangle=(*((pthread_c*)content)).hangle; • summation=(*((pthread_c*)content)).summation; • printf(“thread %d start!\n”,index); • cudaSetDevice(index); • cudaMemcpyToSymbol(cangle,hangle,sizeof(float)*360); 47

  48. Multiple Thread and Multiple GPU • hvector=(float*)malloc(sizeof(float)*size); • cudaMalloc((void**)&dvector,sizeof(float)*size); • bsize=256; • gsize=(int)ceil((float)size/256); • kernel<<<gsize,bsize>>>(dvector,size); • cudaMemcpy(hvector,dvector,sizeof(float)*size,cudaMemcpyDeviceToHost); • for(loop=0;loop<size;loop++) • if(hvector[loop]!=summation) • printf("Error: check result\n"); • free(hvector); • cudaFree(dvector); • cudaError_t error; • if((error=cudaGetLastError())!=cudaSuccess) • printf(“cudaError:%s\n”,cudaGetErrorString(error)); • printf(“thread %d finish!\n”,index); • return NULL; • }; 48

  49. Multiple Thread and Multiple GPU __global__ void kernel(float* dvector,int size) { int loop; int index; float temp; index=blockIdx.x*blockDim.x+threadIdx.x; if(index<size) { for(loop=0,temp=0.0f;loop<360;loop++) temp=temp+cangle[loop]; *(dvector+index)=temp; } return; }; 49

More Related