nanosleep resolution

nanosleep.c

#include <sys/time.h>
#include <sys/resource.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define ONE_SECOND      1000000000L
#define ONE_MS 1000000L

int count = 200;
int debug = 0;

int main (int ac, char **av) {
        double diff;
        struct timespec ts0, ts1, ts2;

        if (ac > 1 && av[1])
                count = strtol(av[1], NULL, 10);

        while(count--) {
        clock_gettime(CLOCK_MONOTONIC, &ts1);

        ts0.tv_sec = 0;
        ts0.tv_nsec = ONE_MS;
        nanosleep(&ts0, NULL);

        clock_gettime(CLOCK_MONOTONIC, &ts2);

                diff = (double)(ts2.tv_nsec - ts1.tv_nsec)/1e9;
                diff += (double)(ts2.tv_sec - ts1.tv_sec);
                if (debug)
                        printf("(%ld.%.6ld) ", ts2.tv_sec, ts2.tv_nsec);
                printf("%.6f\n", diff*1000);
        }
        return 0;
}

result.txt

$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    2
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 85
Model name:            Intel(R) Xeon(R) Platinum 8163 CPU @ 2.50GHz
Stepping:              4
CPU MHz:               2499.990
BogoMIPS:              4999.98
Hypervisor vendor:     KVM
Virtualization type:   full
L1d cache:             32K
L1i cache:             32K
L2 cache:              1024K
L3 cache:              33792K
NUMA node0 CPU(s):     0-3
Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1
$ ./nanosleep 10
1.065334
1.063151
1.061466
1.067746
1.061667
1.061636
1.062454
1.011586
1.060461
1.060884