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kernel: timeout: optimize z_timeout_expires()

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This currently calls timeout_rem() then adds back the result of
elapsed() to cancel out the subtraction of another elapsed() call
within timeout_rem(). Better not to make any calls to elapsed() in
that case, especially given that elapsed() may incur hardware access
overhead through sys_clock_elapsed().

Let's move the elapsed() subtraction to the only user of timeout_rem()
that needs it and remove its invocation from the z_timeout_expires()
path entirely.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This commit is contained in:
Nicolas Pitre 2024-03-06 11:12:42 -05:00 committed by Carles Cufí
parent 7072e75162
commit c31d646198
1 changed files with 8 additions and 7 deletions
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15
kernel/timeout.c
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@ -160,10 +160,6 @@ static k_ticks_t timeout_rem(const struct _timeout *timeout)
{
k_ticks_t ticks = 0;
if (z_is_inactive_timeout(timeout)) {
return 0;
}
for (struct _timeout *t = first(); t != NULL; t = next(t)) {
ticks += t->dticks;
if (timeout == t) {
@ -171,7 +167,7 @@ static k_ticks_t timeout_rem(const struct _timeout *timeout)
}
}
return ticks - elapsed();
return ticks;
}
k_ticks_t z_timeout_remaining(const struct _timeout *timeout)
@ -179,7 +175,9 @@ k_ticks_t z_timeout_remaining(const struct _timeout *timeout)
k_ticks_t ticks = 0;
K_SPINLOCK(&timeout_lock) {
ticks = timeout_rem(timeout);
if (!z_is_inactive_timeout(timeout)) {
ticks = timeout_rem(timeout) - elapsed();
}
}
return ticks;
@ -190,7 +188,10 @@ k_ticks_t z_timeout_expires(const struct _timeout *timeout)
k_ticks_t ticks = 0;
K_SPINLOCK(&timeout_lock) {
ticks = curr_tick + timeout_rem(timeout) + elapsed();
ticks = curr_tick;
if (!z_is_inactive_timeout(timeout)) {
ticks += timeout_rem(timeout);
}
}
return ticks;