From: Claudio Jeker <cjeker@diehard.n-r-g.com>
Subject: Re: use nanoseconds for timekeeping in hfsc
To: David Gwynne <david@gwynne.id.au>
Cc: tech@openbsd.org
Date: Mon, 28 Oct 2024 13:00:41 +0100

On Fri, Oct 25, 2024 at 03:11:25PM +1000, David Gwynne wrote:
> hfsc uses a scaled version of microseconds for time at the moment. it
> seems more straightforward to just use nanoseconds.
> 
> kjc and cheloa like the idea. it seems to work fine in my own tests.
> 
> ok?

OK claudio@. Only think I wonder is why we need hfsc_uptime() instead of
using nsecuptime() in the code? It is an extra abstraction that does not
really help.
 
> Index: hfsc.c
> ===================================================================
> RCS file: /cvs/src/sys/net/hfsc.c,v
> diff -u -p -r1.49 hfsc.c
> --- hfsc.c	11 Apr 2023 00:45:09 -0000	1.49
> +++ hfsc.c	30 Sep 2024 05:24:11 -0000
> @@ -248,11 +248,12 @@ void		hfsc_rtsc_min(struct hfsc_runtime_
>  void		hfsc_getclstats(struct hfsc_class_stats *, struct hfsc_class *);
>  struct hfsc_class	*hfsc_clh2cph(struct hfsc_if *, u_int32_t);
>  
> -#define	HFSC_CLK_SHIFT		8
> -#define	HFSC_FREQ		(1000000 << HFSC_CLK_SHIFT)
> -#define	HFSC_CLK_PER_TICK	(HFSC_FREQ / hz)
> +#define	HFSC_FREQ		1000000000LL
> +#define	HFSC_CLK_PER_TICK	tick_nsec
>  #define	HFSC_HT_INFINITY	0xffffffffffffffffLL /* infinite time value */
>  
> +#define hfsc_uptime()		nsecuptime()
> +
>  struct pool	hfsc_class_pl, hfsc_internal_sc_pl;
>  
>  /*
> @@ -345,16 +346,6 @@ hfsc_class_purge(struct hfsc_class *cl, 
>  		return cl->cl_qops->pfq_purge(cl->cl_qdata, ml);
>  }
>  
> -u_int64_t
> -hfsc_microuptime(void)
> -{
> -	struct timeval tv;
> -
> -	microuptime(&tv);
> -	return (((u_int64_t)(tv.tv_sec) * 1000000 + tv.tv_usec) <<
> -	    HFSC_CLK_SHIFT);
> -}
> -
>  static inline u_int
>  hfsc_more_slots(u_int current)
>  {
> @@ -845,7 +836,7 @@ hfsc_deq_begin(struct ifqueue *ifq, void
>  	struct mbuf *m;
>  	u_int64_t cur_time;
>  
> -	cur_time = hfsc_microuptime();
> +	cur_time = hfsc_uptime();
>  
>  	/*
>  	 * if there are eligible classes, use real-time criteria.
> @@ -1007,7 +998,7 @@ hfsc_init_ed(struct hfsc_if *hif, struct
>  {
>  	u_int64_t cur_time;
>  
> -	cur_time = hfsc_microuptime();
> +	cur_time = hfsc_uptime();
>  
>  	/* update the deadline curve */
>  	hfsc_rtsc_min(&cl->cl_deadline, cl->cl_rsc, cur_time, cl->cl_cumul);
> @@ -1114,7 +1105,7 @@ hfsc_init_vf(struct hfsc_class *cl, int 
>  			if (cl->cl_usc != NULL) {
>  				/* class has upper limit curve */
>  				if (cur_time == 0)
> -					cur_time = hfsc_microuptime();
> +					cur_time = hfsc_uptime();
>  
>  				/* update the ulimit curve */
>  				hfsc_rtsc_min(&cl->cl_ulimit, cl->cl_usc, cur_time,
> @@ -1701,7 +1692,7 @@ hfsc_getclstats(struct hfsc_class_stats 
>  	sp->myfadj = cl->cl_myfadj;
>  	sp->vtadj = cl->cl_vtadj;
>  
> -	sp->cur_time = hfsc_microuptime();
> +	sp->cur_time = hfsc_uptime();
>  	sp->machclk_freq = HFSC_FREQ;
>  
>  	sp->qlength = hfsc_class_qlength(cl);
> 

-- 
:wq Claudio