Commit 31caec79 authored by Simon Marlow's avatar Simon Marlow

Set thread affinity with +RTS -qa (only on Linux so far)

parent 75833842
......@@ -1029,7 +1029,7 @@ dnl off_t, because it will affect the result of that test.
AC_SYS_LARGEFILE
dnl ** check for specific header (.h) files that we are interested in
AC_CHECK_HEADERS([bfd.h ctype.h dirent.h dlfcn.h errno.h fcntl.h grp.h limits.h locale.h nlist.h pthread.h pwd.h signal.h sys/mman.h sys/resource.h sys/time.h sys/timeb.h sys/timers.h sys/times.h sys/utsname.h sys/wait.h termios.h time.h utime.h windows.h winsock.h])
AC_CHECK_HEADERS([bfd.h ctype.h dirent.h dlfcn.h errno.h fcntl.h grp.h limits.h locale.h nlist.h pthread.h pwd.h signal.h sys/mman.h sys/resource.h sys/time.h sys/timeb.h sys/timers.h sys/times.h sys/utsname.h sys/wait.h termios.h time.h utime.h windows.h winsock.h sched.h])
dnl ** check if it is safe to include both <time.h> and <sys/time.h>
AC_HEADER_TIME
......@@ -1107,7 +1107,7 @@ fi
dnl ** check for more functions
dnl ** The following have been verified to be used in ghc/, but might be used somewhere else, too.
AC_CHECK_FUNCS([getclock getrusage gettimeofday setitimer siginterrupt sysconf times ctime_r])
AC_CHECK_FUNCS([getclock getrusage gettimeofday setitimer siginterrupt sysconf times ctime_r, sched_setaffinity])
AC_TRY_RUN([
#include <sys/types.h>
......
......@@ -186,8 +186,8 @@ void setThreadLocalVar (ThreadLocalKey *key, void *value);
void freeThreadLocalKey (ThreadLocalKey *key);
// Processors and affinity
nat getNumberOfProcessors (void);
nat getNumberOfProcessors (void);
void setThreadAffinity (nat n, nat m);
#endif // !CMINUSMINUS
#else
......
......@@ -192,6 +192,7 @@ struct PAR_FLAGS {
rtsBool parGcGen; /* do parallel GC in this generation
* and higher only */
rtsBool parGcLoadBalancing; /* do load-balancing in parallel GC */
rtsBool setAffinity; /* force thread affinity with CPUs */
};
#endif /* THREADED_RTS */
......
......@@ -233,6 +233,7 @@ void initRtsFlagsDefaults(void)
RtsFlags.ParFlags.parGcEnabled = 1;
RtsFlags.ParFlags.parGcGen = 1;
RtsFlags.ParFlags.parGcLoadBalancing = 1;
RtsFlags.ParFlags.setAffinity = 0;
#endif
#ifdef PAR
......@@ -476,6 +477,8 @@ usage_text[] = {
" -N Determine the number of processors to use automatically",
" -q1 Use one OS thread for GC (turns off parallel GC)",
" -qg<n> Use parallel GC only for generations >= <n> (default: 1)",
" -qb Disable load-balancing in the parallel GC",
" -qa Use the OS to set thread affinity",
" -qm Don't automatically migrate threads between CPUs",
" -qw Migrate a thread to the current CPU when it is woken up",
#endif
......@@ -1233,6 +1236,9 @@ error = rtsTrue;
case 'b':
RtsFlags.ParFlags.parGcLoadBalancing = rtsFalse;
break;
case 'a':
RtsFlags.ParFlags.setAffinity = rtsTrue;
break;
case 'm':
RtsFlags.ParFlags.migrate = rtsFalse;
break;
......
......@@ -2125,6 +2125,10 @@ workerStart(Task *task)
cap = task->cap;
RELEASE_LOCK(&task->lock);
if (RtsFlags.ParFlags.setAffinity) {
setThreadAffinity(cap->no, n_capabilities);
}
// set the thread-local pointer to the Task:
taskEnter(task);
......
......@@ -7,8 +7,9 @@
*
* --------------------------------------------------------------------------*/
#if defined(DEBUG) && defined(__linux__)
#if defined(__linux__)
/* We want GNU extensions in DEBUG mode for mutex error checking */
/* We also want the affinity API, which requires _GNU_SOURCE */
#define _GNU_SOURCE
#endif
......@@ -26,6 +27,10 @@
#error pthreads.h is required for the threaded RTS on Posix platforms
#endif
#if defined(HAVE_SCHED_H)
#include <sched.h>
#endif
/*
* This (allegedly) OS threads independent layer was initially
* abstracted away from code that used Pthreads, so the functions
......@@ -197,6 +202,26 @@ getNumberOfProcessors (void)
return nproc;
}
// Schedules the thread to run on CPU n of m. m may be less than the
// number of physical CPUs, in which case, the thread will be allowed
// to run on CPU n, n+m, n+2m etc.
void
setThreadAffinity (nat n, nat m)
{
#if defined(HAVE_SCHED_H) && defined(HAVE_SCHED_SETAFFINITY)
nat nproc;
cpu_set_t cs;
nat i;
nproc = getNumberOfProcessors();
CPU_ZERO(&cs);
for (i = n; i < nproc; i+=m) {
CPU_SET(n, &cs);
}
sched_setaffinity(0, sizeof(cpu_set_t), &cs);
#endif
}
#else /* !defined(THREADED_RTS) */
int
......
......@@ -246,6 +246,12 @@ getNumberOfProcessors (void)
return nproc;
}
void
setThreadAffinity (nat n STG_UNUSED, nat m STG_UNUSED)
{
/* ToDo */
}
#else /* !defined(THREADED_RTS) */
int
......
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