Skip site navigation (1)Skip section navigation (2) 
Date:      Mon, 9 Sep 2019 11:31:32 -0700
From:      Conrad Meyer <cem@freebsd.org>
To:        Konstantin Belousov <kib@freebsd.org>
Cc:        src-committers@freebsd.org, svn-src-all@freebsd.org,  svn-src-head@freebsd.org
Subject:   Re: svn commit: r352059 - head/sys/kern
Message-ID:  <CAG6CVpXyhxDc=D0ZWXoQeFPr6A3CrOK1MNeO7MVmjc4uVYTBvQ@mail.gmail.com>
In-Reply-To: <201909091129.x89BTxvw061871@repo.freebsd.org>
References:  <201909091129.x89BTxvw061871@repo.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help 
What=E2=80=99s the motivation for using more timehands?

On Mon, Sep 9, 2019 at 04:30 Konstantin Belousov <kib@freebsd.org> wrote:

> Author: kib
> Date: Mon Sep  9 11:29:58 2019
> New Revision: 352059
> URL: https://svnweb.freebsd.org/changeset/base/352059
>
> Log:
>   Make timehands count selectable at boottime.
>
>   Tested by:    O'Connor, Daniel <darius@dons.net.au>
>   Sponsored by: The FreeBSD Foundation
>   MFC after:    1 week
>   Differential revision:        https://reviews.freebsd.org/D21563
>
> Modified:
>   head/sys/kern/kern_tc.c
>
> Modified: head/sys/kern/kern_tc.c
>
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D
> --- head/sys/kern/kern_tc.c     Mon Sep  9 11:22:38 2019        (r352058)
> +++ head/sys/kern/kern_tc.c     Mon Sep  9 11:29:58 2019        (r352059)
> @@ -83,19 +83,16 @@ struct timehands {
>         struct timehands        *th_next;
>  };
>
> -static struct timehands th0;
> -static struct timehands th1 =3D {
> -       .th_next =3D &th0
> -};
> -static struct timehands th0 =3D {
> +static struct timehands ths[16] =3D {
> +    [0] =3D  {
>         .th_counter =3D &dummy_timecounter,
>         .th_scale =3D (uint64_t)-1 / 1000000,
>         .th_offset =3D { .sec =3D 1 },
>         .th_generation =3D 1,
> -       .th_next =3D &th1
> +    },
>  };
>
> -static struct timehands *volatile timehands =3D &th0;
> +static struct timehands *volatile timehands =3D &ths[0];
>  struct timecounter *timecounter =3D &dummy_timecounter;
>  static struct timecounter *timecounters =3D &dummy_timecounter;
>
> @@ -115,6 +112,10 @@ static int timestepwarnings;
>  SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
>      &timestepwarnings, 0, "Log time steps");
>
> +static int timehands_count =3D 2;
> +SYSCTL_INT(_kern_timecounter, OID_AUTO, timehands_count, CTLFLAG_RDTUN,
> +    &timehands_count, 0, "Count of timehands in rotation");
> +
>  struct bintime bt_timethreshold;
>  struct bintime bt_tickthreshold;
>  sbintime_t sbt_timethreshold;
> @@ -1960,8 +1961,9 @@ done:
>  static void
>  inittimecounter(void *dummy)
>  {
> +       struct timehands *thp;
>         u_int p;
> -       int tick_rate;
> +       int i, tick_rate;
>
>         /*
>          * Set the initial timeout to
> @@ -1987,6 +1989,16 @@ inittimecounter(void *dummy)
>  #ifdef FFCLOCK
>         ffclock_init();
>  #endif
> +
> +       /* Set up the requested number of timehands. */
> +       if (timehands_count < 1)
> +               timehands_count =3D 1;
> +       if (timehands_count > nitems(ths))
> +               timehands_count =3D nitems(ths);
> +       for (i =3D 1, thp =3D &ths[0]; i < timehands_count;  thp =3D &ths=
[i++])
> +               thp->th_next =3D &ths[i];
> +       thp->th_next =3D &ths[0];
> +
>         /* warm up new timecounter (again) and get rolling. */
>         (void)timecounter->tc_get_timecount(timecounter);
>         (void)timecounter->tc_get_timecount(timecounter);
>
>

Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAG6CVpXyhxDc=D0ZWXoQeFPr6A3CrOK1MNeO7MVmjc4uVYTBvQ>