[PATCH v8 9/9] tools/xenstored: use xenmanage_poll_changed_domain()

[Juergen Gross <jgross@xxxxxxxx>]

Instead of checking each known domain after having received a
VIRQ_DOM_EXC event, use the new xenmanage_poll_changed_domain()
function for directly getting the domid of a domain having changed
its state.

A test doing "xl shutdown" of 1000 guests has shown to reduce the
consumed cpu time of xenstored by 6% with this change applied.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V8:
- new patch
---
 tools/xenstored/domain.c | 64 +++++++++++++++++++++++++++++-----------
 1 file changed, 46 insertions(+), 18 deletions(-)

diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 63df24030e..ad16a00ce3 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -621,30 +621,24 @@ static int destroy_domain(void *_domain)
        return 0;
 }
 
-static int check_domain(const void *k, void *v, void *arg)
+static int do_check_domain(struct domain *domain, bool *notify,
+                          unsigned int state, uint64_t unique_id)
 {
-       unsigned int state;
        struct connection *conn;
-       int dom_invalid;
-       struct domain *domain = v;
-       bool *notify = arg;
-       uint64_t unique_id;
 
-       dom_invalid = xenmanage_get_domain_info(xm_handle, domain->domid,
-                                               &state, &unique_id);
-       if (!dom_invalid) {
+       if (unique_id) {
                if (!domain->unique_id)
                        domain->unique_id = unique_id;
                else if (domain->unique_id != unique_id)
-                       dom_invalid = 1;
+                       unique_id = 0;
        }
 
        if (!domain->introduced) {
-               if (dom_invalid)
+               if (!unique_id)
                        talloc_free(domain);
                return 0;
        }
-       if (!dom_invalid) {
+       if (unique_id) {
                if ((state & XENMANAGE_GETDOMSTATE_STATE_SHUTDOWN)
                    && !domain->shutdown) {
                        domain->shutdown = true;
@@ -667,6 +661,21 @@ static int check_domain(const void *k, void *v, void *arg)
        return 0;
 }
 
+static int check_domain(const void *k, void *v, void *arg)
+{
+       struct domain *domain = v;
+       unsigned int state;
+       uint64_t unique_id;
+
+       if (xenmanage_get_domain_info(xm_handle, domain->domid, &state,
+                                     &unique_id)) {
+               unique_id = 0;
+               state = 0;
+       }
+
+       return do_check_domain(domain, arg, state, unique_id);
+}
+
 void check_domains(void)
 {
        bool notify = false;
@@ -678,6 +687,30 @@ void check_domains(void)
                fire_special_watches("@releaseDomain");
 }
 
+static struct domain *find_domain_struct(unsigned int domid)
+{
+       return hashtable_search(domhash, &domid);
+}
+
+static void do_check_domains(void)
+{
+       unsigned int domid;
+       unsigned int state;
+       uint64_t unique_id;
+       struct domain *domain;
+       bool notify = false;
+
+       while (!xenmanage_poll_changed_domain(xm_handle, &domid, &state,
+                                             &unique_id)) {
+               domain = find_domain_struct(domid);
+               if (domain)
+                       do_check_domain(domain, &notify, state, unique_id);
+       }
+
+       if (notify)
+               fire_special_watches("@releaseDomain");
+}
+
 /* We scan all domains rather than use the information given here. */
 void handle_event(void)
 {
@@ -687,7 +720,7 @@ void handle_event(void)
                barf_perror("Failed to read from event fd");
 
        if (port == virq_port)
-               check_domains();
+               do_check_domains();
 
        if (xenevtchn_unmask(xce_handle, port) == -1)
                barf_perror("Failed to write to event fd");
@@ -698,11 +731,6 @@ static char *talloc_domain_path(const void *context, 
unsigned int domid)
        return talloc_asprintf(context, "/local/domain/%u", domid);
 }
 
-static struct domain *find_domain_struct(unsigned int domid)
-{
-       return hashtable_search(domhash, &domid);
-}
-
 int domain_get_quota(const void *ctx, struct connection *conn,
                     unsigned int domid)
 {
-- 
2.43.0