Hey Thomas,
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> } while (read_seqcount_retry(&tk_core.seq, seq));
>
> - return base;
> -
> + return base + nsecs;
The rest of the file seems to use `ktime_add_ns(base, nsecs)`. I
realize, of course, that these days that macro is the same thing as
what you wrote, though.
I can confirm that this fixes it (see below), so you can add my
Tested-by if you want or care.
One thing I'm curious about is the performance comparison with various
ways of using jiffies directly:
ktime_mono_to_any(ns_to_ktime(jiffies64_to_nsecs(get_jiffies_64())),
TK_OFFS_BOOT)
Or really giving up on the locking:
ktime_to_ns(tk_core.timekeeper.offs_boot) + jiffies64_to_nsecs(get_jiffies_64())
Or keeping things in units of jiffies, though that incurs a div_u64:
nsecs_to_jiffies64(ktime_to_ns(tk_core.timekeeper.offs_boot)) + get_jiffies_64()
But since offs_boot is updated somewhat rarely, that div_u64 could be
precomputed each time offs_boot is updated, allowing hypothetically:
tk_core.timekeeper.offs_boot_jiffies + get_jiffies_64()
Which then could be remade into a wrapper such as:
get_jiffies_boot_64()
The speed is indeed an important factor to me in accessing this time
value. Are any of these remotely interesting to you in that light?
Maybe I'll send a patch for the latter.
Jason
8<-----------------
int __init mod_init(void)
{
u64 j1 = 0, j2, k1 = 0, k2, c1 = 0, c2, l1 = 0, l2;
for (;;) {
j2 = jiffies64_to_nsecs(get_jiffies_64());
k2 =
ktime_to_ns(ktime_mono_to_any(ns_to_ktime(jiffies64_to_nsecs(get_jiffies_64())),
TK_OFFS_BOOT));
c2 = ktime_get_coarse_boottime();
l2 = local_clock();
pr_err("%llu %llu %llu %llu\n", j2 - j1, k2 - k1, c2 - c1, l2 - l1);
j1 = j2;
k1 = k2;
c1 = c2;
l1 = l2;
msleep(200);
}
return 0;
}
[ 0.420861] wireguard: 17179569472000000 17179569472000000
312696682 420860781
[ 0.628656] wireguard: 208000000 208000000 208000000 207791083
[ 0.836591] wireguard: 208000000 208000000 208000000 207934734
[ 1.044728] wireguard: 208000000 208000000 208000000 208137167
[ 1.252593] wireguard: 208000000 208000000 208000000 207862974
[ 1.460815] wireguard: 208000000 208000000 208000000 208223514
[ 1.668667] wireguard: 208000000 208000000 208000000 207852437
[ 1.876438] wireguard: 208000000 208000000 208000000 207773658
[ 2.084627] wireguard: 208000000 208000000 208000000 208185643
[ 2.292690] wireguard: 208000000 208000000 208000000 208063377
[ 2.500672] wireguard: 208000000 208000000 208000000 207982209
[ 2.708658] wireguard: 208000000 208000000 208000000 207986527
[ 2.916686] wireguard: 208000000 208000000 208000000 208026945
[ 3.124732] wireguard: 208000000 208000000 208000000 208046153
[ 3.332684] wireguard: 208000000 208000000 208000000 207952302
[ 3.540668] wireguard: 208000000 208000000 208000000 207978195
[ 3.748633] wireguard: 208000000 208000000 208000000 207970981
[ 3.956686] wireguard: 208000000 208000000 208000000 208053094
[ 4.164690] wireguard: 208000000 208000000 208000000 207995376
[ 4.372660] wireguard: 208000000 208000000 208000000 207978324
[ 4.580787] wireguard: 208000000 208000000 208000000 208126491
[ 4.788716] wireguard: 208000000 208000000 208000000 207930106
[ 4.996685] wireguard: 208000000 208000000 208000000 207968555
[ 5.204673] wireguard: 208000000 208000000 208000000 207988295
[ 5.412676] wireguard: 208000000 208000000 208000000 207991396
[ 5.620648] wireguard: 208000000 208000000 208000000 207983671
[ 5.828822] wireguard: 208000000 208000000 208000000 208174230
[ 6.036596] wireguard: 208000000 208000000 208000000 207773401
[ 6.244615] wireguard: 208000000 208000000 208000000 208017986
[ 6.452625] wireguard: 208000000 208000000 208000000 208011215
[ 6.660678] wireguard: 208000000 208000000 208000000 208053134
[ 6.868609] wireguard: 208000000 208000000 208000000 207929536
