Some of APIs invoke a system call to get time or clock. But, a system call from a VE program takes time because communication between VE and VH is required.
So, some of them are implemented to get time or clock quickly by reducing the invocation of a system call. They invoke a system call at the first time only. They do not invoke any system call at the next time. They read a counter of VE, calculate time or clock and return the result. We call them as "quick call implementation".
The below is the current status of VEOS v2.6.2 which was released on 31st July. 2020.
| API |
option |
available? |
quick?
|
| gettimeofday() |
|
Yes |
Yes
|
| clock_gettime() |
CLOCK_REALTIME |
Yes |
Yes
|
| clock_gettime() |
CLOCK_REALTIME_COARSE |
Yes |
Yes
|
| clock_gettime() |
CLOCK_MONOTONIC |
Yes |
Yes
|
| clock_gettime() |
CLOCK_MONOTONIC_COARSE |
Yes |
Yes
|
| clock_gettime() |
CLOCK_MONOTONIC_RAW |
Yes |
Yes
|
| clock_gettime() |
CLOCK_BOOTTIME |
Yes |
Yes
|
| clock_gettime() |
CLOCK_PROCESS_CPUTIME_ID |
Yes |
No
|
| clock_gettime() |
CLOCK_THREAD_CPUTIME_ID |
Yes |
Yes
|
| clock_gettime() |
The clock id returned by pthread_getcpuclockid() |
Yes |
No
|
| clock_gettime() |
The clock id returned by clock_getcpuclockid() |
Yes |
No
|
| getrusage() |
RUSAGE_SELF |
Yes |
No
|
| getrusage() |
RUSAGE_CHILDREN |
Yes |
No
|
| getrusage() |
RUSAGE_THREAD |
Yes |
No
|
| clock() |
|
Yes |
No
|
| time() |
|
Yes |
No
|
| times() |
|
Yes |
No
|
If your program invokes an API to get time or clock frequently, please invoke an API which is quick call implementation, to get better performance.
| Posted by NEC admin (administrator) on 23 June 2022 at 01:18. |
|