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MEDIUM: resolvers: Stop scheduling resolution during stopping stage

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When the process is stopping, the server resolutions are suspended. However
the task is still periodically woken up for nothing. If there is a huge
number of resolution, it may lead to a noticeable CPU consumption for no
reason.

To avoid this extra CPU cost, we stop to schedule the the resolution tasks
during the stopping stage. Of course, it is only true for server
resolutinos. Dynamic ones, via do-resolve actions, are not concerned. These
ones must still be triggered during stopping stage.

Concretly, during the stopping stage, the resolvers task is no longer
scheduled if there is no running resolutions. In this case, if a do-resolve
action is evaluated, the task is woken up.

This patch should partially solve the issue #2145.
This commit is contained in:
Christopher Faulet 2023-05-16 18:28:57 +02:00
parent 8bca3cc8c7
commit 06e9c81bd0
1 changed files with 4 additions and 1 deletions
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5
src/resolvers.c
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@ -459,7 +459,7 @@ void resolv_trigger_resolution(struct resolv_requester *req)
/* The resolution must not be triggered yet. Use the cached response, if
* valid */
exp = tick_add(res->last_resolution, resolvers->hold.valid);
if (resolvers->t && (res->status != RSLV_STATUS_VALID ||
if (resolvers->t && (!tick_isset(resolvers->t->expire) || res->status != RSLV_STATUS_VALID ||
!tick_isset(res->last_resolution) || tick_is_expired(exp, now_ms))) {
/* If the resolution is not running and the requester is a
* server, reset the resolution timer to force a quick
@ -2457,6 +2457,9 @@ struct task *process_resolvers(struct task *t, void *context, unsigned int state
if (unlikely(stopping)) {
struct dns_nameserver *ns;
if (LIST_ISEMPTY(&resolvers->resolutions.curr))
t->expire = TICK_ETERNITY;
list_for_each_entry(ns, &resolvers->nameservers, list) {
if (ns->stream)
task_wakeup(ns->stream->task_idle, TASK_WOKEN_MSG);