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sd-event: try to move timer wakeups to the same spot within each minute

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This commit is contained in:
Lennart Poettering 2013-11-21 00:46:13 +01:00
parent 2e41a51ea4
commit 850516e012
2 changed files with 22 additions and 12 deletions
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2
TODO
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@ -49,8 +49,6 @@ Features:
* timer: expose accuracy as unit setting
* sd-event: do per-minute coalescing of timer events too
* when we detect low battery and no AC on boot, show pretty splash and refuse boot
* move libasyncns into systemd as libsystemd-asyncns

32
src/libsystemd-bus/sd-event.c
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@ -640,15 +640,16 @@ static int event_setup_timer_fd(
}
/* When we sleep for longer, we try to realign the wakeup to
the same time wihtin each second, so that events all across
the system can be coalesced into a single CPU
wakeup. However, let's take some system-specific randomness
for this value, so that in a network of systems with synced
clocks timer events are distributed a bit. Here, we
calculate a perturbation usec offset from the boot ID. */
the same time wihtin each minute/second/250ms, so that
events all across the system can be coalesced into a single
CPU wakeup. However, let's take some system-specific
randomness for this value, so that in a network of systems
with synced clocks timer events are distributed a
bit. Here, we calculate a perturbation usec offset from the
boot ID. */
if (sd_id128_get_boot(&bootid) >= 0)
e->perturb = (bootid.qwords[0] ^ bootid.qwords[1]) % USEC_PER_SEC;
e->perturb = (bootid.qwords[0] ^ bootid.qwords[1]) % USEC_PER_MINUTE;
*timer_fd = fd;
return 0;
@ -1363,13 +1364,24 @@ static usec_t sleep_between(sd_event *e, usec_t a, usec_t b) {
dispatch as much as possible on the entire system.
We implement this by waking up everywhere at the same time
within any given second if we can, synchronised via the
within any given minute if we can, synchronised via the
perturbation value determined from the boot ID. If we can't,
then we try to find the same spot in every a 250ms
then we try to find the same spot in every 1s and then 250ms
step. Otherwise, we pick the last possible time to wake up.
*/
c = (b / USEC_PER_SEC) * USEC_PER_SEC + e->perturb;
c = (b / USEC_PER_MINUTE) * USEC_PER_MINUTE + e->perturb;
if (c >= b) {
if (_unlikely_(c < USEC_PER_MINUTE))
return b;
c -= USEC_PER_MINUTE;
}
if (c >= a)
return c;
c = (b / USEC_PER_SEC) * USEC_PER_SEC + (e->perturb % USEC_PER_SEC);
if (c >= b) {
if (_unlikely_(c < USEC_PER_SEC))
return b;