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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 * 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 * when we detect low battery and no AC on boot, show pretty splash and refuse boot
* move libasyncns into systemd as libsystemd-asyncns * move libasyncns into systemd as libsystemd-asyncns

32
src/libsystemd-bus/sd-event.c
View File

@ -640,15 +640,16 @@ static int event_setup_timer_fd(
} }
/* When we sleep for longer, we try to realign the wakeup to /* When we sleep for longer, we try to realign the wakeup to
the same time wihtin each second, so that events all across the same time wihtin each minute/second/250ms, so that
the system can be coalesced into a single CPU events all across the system can be coalesced into a single
wakeup. However, let's take some system-specific randomness CPU wakeup. However, let's take some system-specific
for this value, so that in a network of systems with synced randomness for this value, so that in a network of systems
clocks timer events are distributed a bit. Here, we with synced clocks timer events are distributed a
calculate a perturbation usec offset from the boot ID. */ bit. Here, we calculate a perturbation usec offset from the
boot ID. */
if (sd_id128_get_boot(&bootid) >= 0) 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; *timer_fd = fd;
return 0; 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. dispatch as much as possible on the entire system.
We implement this by waking up everywhere at the same time 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, 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. 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 (c >= b) {
if (_unlikely_(c < USEC_PER_SEC)) if (_unlikely_(c < USEC_PER_SEC))
return b; return b;