Re: Feedback Request: Standardizing Time Helpers

Forwarding to hackers@ since Nick isn't subscribed and the original email didn't reach.

On Tue, Sep 30, 2025 at 10:10:14AM -0400, Nick Banks wrote:
N> Hello All,
N> 
N> For the last few weeks I've been refactoring the HPTS code (tcp_hpts.c),
N> with one ultimate goal of eliminating the hard dependencies with TCP so the
N> HPTS code may be used in the future for other high performance timing
N> scenarios.
N> 
N> My latest focus is on various constants and macros tcp_hpts.h for
N> converting between different time units and structures. For instance:
N> 
N> #define HPTS_USEC_IN_SEC 1000000
N> #define HPTS_MSEC_IN_SEC 1000
N> #define HPTS_USEC_IN_MSEC 1000
N> 
N> static inline uint32_t
N> tcp_tv_to_usec(const struct timeval *sv)
N> {
N> return ((uint32_t) ((sv->tv_sec * HPTS_USEC_IN_SEC) + sv->tv_usec));
N> }
N> 
N> static inline uint32_t
N> tcp_tv_to_msec(const struct timeval *sv)
N> {
N> return ((uint32_t) ((sv->tv_sec * HPTS_MSEC_IN_SEC) + (sv->tv_usec/
N> HPTS_USEC_IN_MSEC)));
N> }
N> 
N> static inline uint64_t
N> tcp_tv_to_lusec(const struct timeval *sv)
N> {
N> return ((uint64_t)((sv->tv_sec * HPTS_USEC_IN_SEC) + sv->tv_usec));
N> }
N> 
N> My goal is to standardize these and move them out of the HPTS & TCP code,
N> if possible. One possible location could be time.h where many of the
N> related dependencies are already. But, depending on how we move forward, we
N> obviously need to be careful about collisions with pre-existing user mode
N> code. So, perhaps the new defines could be wrapped with _KERNEL and some
N> opt-in flag (or possibly __BSD_VISIBLE), such as what I have below?
N> 
N> #if defined(_KERNEL) || defined(__BSD_VISIBLE)
N> /*
N> * Time unit conversion constants
N> */
N> #define USEC_IN_SEC 1000000L /* microseconds per second */
N> #define MSEC_IN_SEC 1000L /* milliseconds per second */
N> #define USEC_IN_MSEC 1000L /* microseconds per millisecond */
N> 
N> /*
N> * Time unit conversion macros
N> */
N> #define USEC_TO_MSEC(x) ((x) / USEC_IN_MSEC) /* microseconds to
N> milliseconds */
N> #define MSEC_TO_USEC(x) ((x) * USEC_IN_MSEC) /* milliseconds to
N> microseconds */
N> #define USEC_TO_SEC(x) ((x) / USEC_IN_SEC) /* microseconds to seconds */
N> #define SEC_TO_USEC(x) ((x) * USEC_IN_SEC) /* seconds to microseconds */
N> #define USEC64_TO_MSEC(x) ((uint32_t)((x) / USEC_IN_MSEC)) /* 64-bit usec
N> timestamp to msec */
N> 
N> /*
N> * Timeval conversion macros
N> */
N> #define timeval_to_usec(tv) ((uint32_t)(((tv)->tv_sec * USEC_IN_SEC) +
N> (tv)->tv_usec))
N> #define timeval_to_msec(tv) ((uint32_t)(((tv)->tv_sec * MSEC_IN_SEC) +
N> ((tv)->tv_usec / USEC_IN_MSEC)))
N> #define timeval_to_usec64(tv) ((uint64_t)(((tv)->tv_sec * USEC_IN_SEC) +
N> (tv)->tv_usec))
N> #endif /* _KERNEL || __BSD_VISIBLE */
N> 
N> I'd appreciate any suggestion on how best to proceed here. Is there an
N> appetite to have a common place for these kinds of definitions, outside of
N> networking?
N> 
N> Thanks,
N> - Nick

-- 
Gleb Smirnoff