Messages in this thread | | | From | Jason Vas Dias <> | Date | Sat, 17 Mar 2018 23:37:39 +0000 | Subject | Re: [PATCH v4.16-rc5 (2)] x86/vdso: VDSO should handle clock_gettime(CLOCK_MONOTONIC_RAW) without syscall |
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fixed typo in timer_latency.c affecting only -r <repeat> printout :
$ gcc -DN_SAMPLES=1000 -o timer timer_latency.c CLOCK_MONOTONIC ( using rdtscp_ordered() ) :
$ ./timer -m -r 10 sum: 67615 Total time: 0.000067615S - Average Latency: 0.000000067S N zero deltas: 0 N inconsistent deltas: 0 sum: 51858 Total time: 0.000051858S - Average Latency: 0.000000051S N zero deltas: 0 N inconsistent deltas: 0 sum: 51742 Total time: 0.000051742S - Average Latency: 0.000000051S N zero deltas: 0 N inconsistent deltas: 0 sum: 51944 Total time: 0.000051944S - Average Latency: 0.000000051S N zero deltas: 0 N inconsistent deltas: 0 sum: 51838 Total time: 0.000051838S - Average Latency: 0.000000051S N zero deltas: 0 N inconsistent deltas: 0 sum: 52397 Total time: 0.000052397S - Average Latency: 0.000000052S N zero deltas: 0 N inconsistent deltas: 0 sum: 52428 Total time: 0.000052428S - Average Latency: 0.000000052S N zero deltas: 0 N inconsistent deltas: 0 sum: 52135 Total time: 0.000052135S - Average Latency: 0.000000052S N zero deltas: 0 N inconsistent deltas: 0 sum: 52145 Total time: 0.000052145S - Average Latency: 0.000000052S N zero deltas: 0 N inconsistent deltas: 0 sum: 53116 Total time: 0.000053116S - Average Latency: 0.000000053S N zero deltas: 0 N inconsistent deltas: 0 Average of 10 average latencies of 1000 samples : 0.000000053S
CLOCK_MONOTONIC_RAW ( using rdtscp() ) :
$ ./timer -r 10 sum: 25755 Total time: 0.000025755S - Average Latency: 0.000000025S N zero deltas: 0 N inconsistent deltas: 0 sum: 21614 Total time: 0.000021614S - Average Latency: 0.000000021S N zero deltas: 0 N inconsistent deltas: 0 sum: 21616 Total time: 0.000021616S - Average Latency: 0.000000021S N zero deltas: 0 N inconsistent deltas: 0 sum: 21610 Total time: 0.000021610S - Average Latency: 0.000000021S N zero deltas: 0 N inconsistent deltas: 0 sum: 21619 Total time: 0.000021619S - Average Latency: 0.000000021S N zero deltas: 0 N inconsistent deltas: 0 sum: 21617 Total time: 0.000021617S - Average Latency: 0.000000021S N zero deltas: 0 N inconsistent deltas: 0 sum: 21610 Total time: 0.000021610S - Average Latency: 0.000000021S N zero deltas: 0 N inconsistent deltas: 0 sum: 16940 Total time: 0.000016940S - Average Latency: 0.000000016S N zero deltas: 0 N inconsistent deltas: 0 sum: 16939 Total time: 0.000016939S - Average Latency: 0.000000016S N zero deltas: 0 N inconsistent deltas: 0 sum: 16943 Total time: 0.000016943S - Average Latency: 0.000000016S N zero deltas: 0 N inconsistent deltas: 0 Average of 10 average latencies of 1000 samples : 0.000000019S /* * Program to measure high-res timer latency. * */ #include <stdint.h> #include <stdbool.h> #include <sys/types.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <alloca.h> #include <string.h> #include <stdio.h> #include <stdlib.h>
#ifndef N_SAMPLES #define N_SAMPLES 100 #endif #define _STR(_S_) #_S_ #define STR(_S_) _STR(_S_)
#define TS2NS(_TS_) ((((unsigned long long)(_TS_).tv_sec)*1000000000ULL) + (((unsigned long long)((_TS_).tv_nsec))))
int main(int argc, char *const* argv, char *const* envp) { struct timespec sample[N_SAMPLES+1]; unsigned int cnt=N_SAMPLES, s=0 , avg_n=0; unsigned long long deltas [ N_SAMPLES ] , t1, t2, sum=0, zd=0, ic=0, d , t_start, avg_ns, *avgs=0; clockid_t clk = CLOCK_MONOTONIC_RAW; bool do_dump = false; int argn=1, repeat=1; for(; argn < argc; argn+=1) if( argv[argn] != NULL ) if( *(argv[argn]) == '-') switch( *(argv[argn]+1) ) { case 'm': case 'M': clk = CLOCK_MONOTONIC; break; case 'd': case 'D': do_dump = true; break; case 'r': case 'R': if( (argn < argc) && (argv[argn+1] != NULL)) repeat = atoi(argv[argn+=1]); break; case '?': case 'h': case 'u': case 'U': case 'H': fprintf(stderr,"Usage: timer_latency [\n\t-m : use CLOCK_MONOTONIC clock (not CLOCK_MONOTONIC_RAW)\n\t-d : dump timespec contents. N_SAMPLES: " STR(N_SAMPLES) "\n\t" "-r <repeat count>\n]\t" "Calculates average timer latency (minimum time that can be measured) over N_SAMPLES.\n" ); return 0; } if( repeat > 1 ) { avgs=alloca(sizeof(unsigned long long) * (N_SAMPLES + 1)); if( ((unsigned long) avgs) & 7 ) avgs = ((unsigned long long*)(((unsigned char*)avgs)+(8-((unsigned long) avgs) & 7))); } do { cnt=N_SAMPLES; s=0; do { if( 0 != clock_gettime(clk, &sample[s++]) ) { fprintf(stderr,"oops, clock_gettime() failed: %d: '%s'.\n", errno, strerror(errno)); return 1; } }while( --cnt ); clock_gettime(clk, &sample[s]); for(s=1; s < (N_SAMPLES+1); s+=1) { t1 = TS2NS(sample[s-1]); t2 = TS2NS(sample[s]); if ( (t1 > t2) ||(sample[s-1].tv_sec > sample[s].tv_sec) ||((sample[s-1].tv_sec == sample[s].tv_sec) &&(sample[s-1].tv_nsec > sample[s].tv_nsec) ) ) { fprintf(stderr,"Inconsistency: %llu %llu %lu.%lu %lu.%lu\n", t1 , t2 , sample[s-1].tv_sec, sample[s-1].tv_nsec , sample[s].tv_sec, sample[s].tv_nsec ); ic+=1; continue; } d = t2 - t1; if ( d == 0 ) { zd += 1; } deltas[s-1] = d; if(do_dump) fprintf(stderr, "%lu %lu %llu\n", sample[s].tv_sec, sample[s].tv_nsec, d ); } for(s = 0, sum=0; s < N_SAMPLES; s+=1) sum += deltas[s]; fprintf(stderr,"sum: %llu\n",sum); avg_ns = sum / N_SAMPLES; t_start = TS2NS(sample[0]); t1=(t2 - t_start); printf("Total time: %1.1llu.%9.9lluS - Average Latency: %1.1llu.%9.9lluS N zero deltas: %u N inconsistent deltas: %u\n", t1 / 1000000000, t1 % 1000000000, avg_ns / 1000000000, avg_ns % 1000000000 , zd, ic ); if (avgs != ((void*)0UL)) { avgs[avg_n++] = avg_ns; } } while (--repeat); if (avgs != ((void*)0UL)) { for( s=0, sum=0; s < avg_n; s+=1) sum += avgs[s]; printf("Average of %u average latencies of " STR(N_SAMPLES) " samples : %1.1llu.%9.9lluS\n" , avg_n, (sum / 1000000000LLU)/avg_n, (sum % 1000000000LLU)/avg_n ); } return 0; }
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