From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Piel Date: Thu, 10 Apr 2003 13:13:15 +0000 Subject: [Linux-ia64] [BUG] perfmon doesn't send SIGPROF in kernel 2.5.64 MIME-Version: 1 Content-Type: multipart/mixed; boundary="------------12EC844D083639BCB0E77298" Message-Id: List-Id: To: linux-ia64@vger.kernel.org This is a multi-part message in MIME format. --------------12EC844D083639BCB0E77298 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hello, Since kernel 2.5.60 the perfmon doesn't send SIGPROF to the designated task. The problem can be solved by replacing perfmon.c by an older version (eg: from a kernel 2.5.59). Upgrading to perfmon 1.4 doesn't solve this bug. My testcase is the program "realfeel4" from peter Chubb available on the perfmon website (and attached to this e-mail). On a kernel 2.5.6{0,4} : # ./realfeel4 897.533 MHz secondsPerTick=1.11417e-09 ticksPerSecond=897532585.408894 sample_period = 6282728 smallest = 18446744073709551615, largest = 0, nsamples = 0, sigma = 0, sigmasqr = 0 While we should expect something like on a kernel 2.5.59: # ./realfeel4 897.527 MHz secondsPerTick=1.11417e-09 ticksPerSecond=897526816.648964 sample_period = 6282687 smallest = 4859, largest = 8216, nsamples = 1426, sigma = 7948200, sigmasqr = 44510579922 Mean 5573.77, stddev 382.946 nsamples = 0 means it didn't receive any signal: that's bad :-) It seems the reason of the bug is the new, indirect, way to deliver the signals. Now perfmon relies on do_notify_resume_user() to call pfm_ovfl_block_reset(). I think the bugs stands somewhere there because do_notify_resume_user() isn't called so often (when I tested it, only once the timer of realfeel4 was over). Unfortunatly I didn't understand all the mechanism of the signals and in addition ia64_leave_kernel() is coded in assembly, that doesn't help ;-). I would be very greetful if someone could have a look at it or, at least, could give me some clues about how the kernel decides when to call do_notify_resume_user(). Eric --------------12EC844D083639BCB0E77298 Content-Type: text/plain; charset=us-ascii; name="realfeel4.c" Content-Disposition: inline; filename="realfeel4.c" Content-Transfer-Encoding: 7bit /* * realfeel4.c -- produce histogram of interrupt to user-space latency. * * Based on notify-self.c from the pfmon2.0 package and realfeel.c from * Mark Hahn http://brain.mkmaster.ca/~hahn/realfeel.c * * Portions Copyright (C) 2001-2002 Hewlett-Packard Co * Contributed by Stephane Eranian * * Released under GPL. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include typedef unsigned long stamp_t; static inline stamp_t time_stamp(void) { stamp_t result; __asm__ __volatile__("mov %0=ar.itc;;" : "=r"(result) :: "memory"); return result; } static pid_t me; long sample_period; #define NUM_PMDS PMU_MAX_PMDS static pfarg_reg_t pd[NUM_PMDS]; static pfmlib_param_t evt; static stamp_t smallest = ULONG_MAX; static stamp_t largest; static unsigned long nsamples; static unsigned long sigma; static unsigned long sigmasqr; static void fatal_error(char *fmt,...) __attribute__((noreturn)); static void fatal_error(char *fmt, ...) { va_list ap; va_start(ap, fmt); vfprintf(stderr, fmt, ap); va_end(ap); exit(1); } int set_realtime_priority(void) { struct sched_param schp; /* * set the process to realtime privs */ memset(&schp, 0, sizeof(schp)); schp.sched_priority = sched_get_priority_max(SCHED_FIFO); if (sched_setscheduler(0, SCHED_FIFO, &schp) != 0) { perror("sched_setscheduler"); exit(1); } return 0; } double second() { struct timeval tv; gettimeofday(&tv,0); return tv.tv_sec + 1e-6 * tv.tv_usec; } typedef unsigned long long u64; void selectsleep(unsigned us) { struct timeval tv; tv.tv_sec = 0; tv.tv_usec = us; select(0,0,0,0,&tv); } double secondsPerTick, ticksPerSecond; void calibrate() { double sumx = 0; double sumy = 0; double sumxx = 0; double sumxy = 0; double slope; // least squares linear regression of ticks onto real time // as returned by gettimeofday. const unsigned n = 30; unsigned i; for (i=0; i largest) largest = diff; } last = now; /* * And resume monitoring */ if (perfmonctl(me, PFM_RESTART,NULL, 0) == -1) { perror("PFM_RESTART"); exit(1); } } static void overflow_handler(int n, struct pfm_siginfo *info, struct sigcontext *sc) { unsigned long mask = info->sy_pfm_ovfl[0]; stamp_t now = time_stamp(); /* * Check to see if we received a spurious SIGPROF, i.e., one not * generated by the perfmon subsystem. */ if (info->sy_code != PROF_OVFL) { printf("Received spurious SIGPROF si_code=%d\n", info->sy_code); return; } /* * Each bit set in the overflow mask represents an overflowed counter. * * Here we check that the overflow was caused by our first counter. */ if ((mask & (1UL<< evt.pfp_pc[0].reg_num)) == 0) { printf("Something is wrong, unexpected mask 0x%lx\n", mask); exit(1); } process(now); } int main(int argc, char **argv) { int ret; pfarg_context_t ctx[1]; pfmlib_options_t pfmlib_options; struct sigaction act; me = getpid(); if (mlockall(MCL_CURRENT|MCL_FUTURE) != 0) { perror("mlockall"); exit(1); } set_realtime_priority(); calibrate(); printf("secondsPerTick=%g\n", secondsPerTick); printf("ticksPerSecond=%f\n", ticksPerSecond); /* * Initialize pfm library (required before we can use it) */ if (pfm_initialize() != PFMLIB_SUCCESS) { printf("Can't initialize library\n"); exit(1); } /* * Install the overflow handler (SIGPROF) */ memset(&act, 0, sizeof(act)); act.sa_handler = (sig_t)overflow_handler; act.sa_flags = SA_NOMASK; sigaction(SIGPROF, &act, 0); /* * pass options to library (optional) */ memset(&pfmlib_options, 0, sizeof(pfmlib_options)); pfmlib_options.pfm_debug = 0; /* set to 1 for debug */ pfm_set_options(&pfmlib_options); memset(pd, 0, sizeof(pd)); memset(ctx, 0, sizeof(ctx)); /* * prepare parameters to library. we don't use any Itanium * specific features here. so the pfp_model is NULL. */ memset(&evt, 0, sizeof(evt)); if (pfm_find_event("cpu_cycles", &evt.pfp_events[0].event) != PFMLIB_SUCCESS) { fatal_error("Cannot find cpu_cycles event\n"); } /* * set the default privilege mode for all counters: * PFM_PLM3 : user level * PFM_PLM0 : kernel level */ evt.pfp_dfl_plm = PFM_PLM0|PFM_PLM3; evt.pfp_flags = PFMLIB_PFP_SYSTEMWIDE; /* * how many counters we use */ evt.pfp_event_count = 1; /* * use the library to find the monitors to use */ if ((ret = pfm_dispatch_events(&evt)) != PFMLIB_SUCCESS) { fatal_error("Cannot configure events: %s\n", pfm_strerror(ret)); } /* * For this example, we want to be notified on counter overflows. */ ctx[0].ctx_flags = PFM_FL_SYSTEM_WIDE; ctx[0].ctx_notify_pid = me; ctx[0].ctx_cpu_mask = 1; /* * now create the context for self monitoring/across system */ if (perfmonctl(me, PFM_CREATE_CONTEXT, ctx, 1) == -1 ) { if (errno == ENOSYS) { fatal_error("Your kernel does not have performance monitoring support!\n"); } fatal_error("Can't create PFM context %s\n", strerror(errno)); } /* * Must be done before any PMD/PMD calls (unfreeze PMU). Initialize * PMC/PMD to safe values. psr.up is cleared. */ if (perfmonctl(me, PFM_ENABLE, NULL, 0) == -1) { fatal_error( "child: perfmonctl error PFM_ENABLE errno %d\n",errno); } /* * We want to get notified when the counter used for our first * event overflows */ evt.pfp_pc[0].reg_flags |= PFM_REGFL_OVFL_NOTIFY; pd[0].reg_num = evt.pfp_pc[0].reg_num; /* * we arm the first counter, such that it will overflow * after sample_period events have been observed -- around 7ms */ sample_period = 7 * ticksPerSecond / 1000; printf("sample_period = %lu\n", sample_period); pd[0].reg_value = (~0UL) - sample_period; pd[0].reg_short_reset = (~0UL) - sample_period; pd[0].reg_long_reset = (~0UL) - sample_period; /* * Now program the registers * * We don't use the save variable to indicate the number of elements passed to * the kernel because, as we said earlier, pc may contain more elements than * the number of events we specified, i.e., contains more than counting monitors. */ if (perfmonctl(me, PFM_WRITE_PMCS, evt.pfp_pc, evt.pfp_pc_count) == -1) { fatal_error("child: perfmonctl error PFM_WRITE_PMCS errno %d: %s\n",errno, strerror(errno)); } if (perfmonctl(me, PFM_WRITE_PMDS, pd, evt.pfp_event_count) == -1) { fatal_error( "child: perfmonctl error PFM_WRITE_PMDS errno %d: %s\n",errno, strerror(errno)); } /* * Let's roll now */ perfmonctl(me, PFM_START, 0, 0); delay(10); perfmonctl(me, PFM_STOP, 0, 0); /* * let's stop this now */ if (perfmonctl(me, PFM_DESTROY_CONTEXT, NULL, 0) == -1) { fatal_error( "child: perfmonctl error PFM_DESTROY errno %d\n",errno); } printf("smallest = %lu, largest = %lu, nsamples = %lu, sigma = %lu, sigmasqr = %lu\n", smallest, largest, nsamples, sigma, sigmasqr); if (nsamples) { printf("Mean %g, stddev %g\n", (double)sigma/(double)nsamples, sqrt(((double)sigmasqr - (double)(sigma * sigma)/(double)nsamples)/(double)nsamples)); } return 0; } --------------12EC844D083639BCB0E77298--