This delay can reduce the CPU/IO load storm when autostarting many
guests.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/hypervisor/domain_driver.c | 20 +++++++++++++++++---
 src/hypervisor/domain_driver.h |  1 +
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/hypervisor/domain_driver.c b/src/hypervisor/domain_driver.c
index c5b082fd00..44c8fad4d5 100644
--- a/src/hypervisor/domain_driver.c
+++ b/src/hypervisor/domain_driver.c
@@ -656,11 +656,16 @@ virDomainDriverGetIOThreadsConfig(virDomainDef *targetDef,
     return ret;
 }
 
+typedef struct _virDomainDriverAutoStartState {
+    virDomainDriverAutoStartConfig *cfg;
+    bool first;
+} virDomainDriverAutoStartState;
+
 static int
 virDomainDriverAutoStartOne(virDomainObj *vm,
                             void *opaque)
 {
-    virDomainDriverAutoStartConfig *cfg = opaque;
+    virDomainDriverAutoStartState *state = opaque;
 
     virObjectLock(vm);
     virObjectRef(vm);
@@ -670,7 +675,15 @@ virDomainDriverAutoStartOne(virDomainObj *vm,
 
     if (vm->autostart && !virDomainObjIsActive(vm)) {
         virResetLastError();
-        cfg->callback(vm, cfg->opaque);
+        if (state->cfg->delayMS) {
+            if (!state->first) {
+                g_usleep(state->cfg->delayMS * 1000ull);
+            } else {
+                state->first = false;
+            }
+        }
+
+        state->cfg->callback(vm, state->cfg->opaque);
     }
 
     virDomainObjEndAPI(&vm);
@@ -682,6 +695,7 @@ virDomainDriverAutoStartOne(virDomainObj *vm,
 void virDomainDriverAutoStart(virDomainObjList *domains,
                               virDomainDriverAutoStartConfig *cfg)
 {
+    virDomainDriverAutoStartState state = { .cfg = cfg, .first = true };
     bool autostart;
     VIR_DEBUG("Run autostart stateDir=%s", cfg->stateDir);
     if (virDriverShouldAutostart(cfg->stateDir, &autostart) < 0 ||
@@ -690,5 +704,5 @@ void virDomainDriverAutoStart(virDomainObjList *domains,
         return;
     }
 
-    virDomainObjListForEach(domains, false, virDomainDriverAutoStartOne, cfg);
+    virDomainObjListForEach(domains, false, virDomainDriverAutoStartOne, &state);
 }
diff --git a/src/hypervisor/domain_driver.h b/src/hypervisor/domain_driver.h
index c27ed9155e..d695e26f90 100644
--- a/src/hypervisor/domain_driver.h
+++ b/src/hypervisor/domain_driver.h
@@ -84,6 +84,7 @@ typedef struct _virDomainDriverAutoStartConfig {
     char *stateDir;
     virDomainDriverAutoStartCallback callback;
     void *opaque;
+    int delayMS; /* milliseconds between starting each guest */
 } virDomainDriverAutoStartConfig;
 
 void virDomainDriverAutoStart(virDomainObjList *domains,
-- 
2.47.1

On Wed, Jan 08, 2025 at 19:42:38 +0000, Daniel P. Berrangé wrote:
> This delay can reduce the CPU/IO load storm when autostarting many
> guests.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  src/hypervisor/domain_driver.c | 20 +++++++++++++++++---
>  src/hypervisor/domain_driver.h |  1 +
>  2 files changed, 18 insertions(+), 3 deletions(-)

[...]

> diff --git a/src/hypervisor/domain_driver.h b/src/hypervisor/domain_driver.h
> index c27ed9155e..d695e26f90 100644
> --- a/src/hypervisor/domain_driver.h
> +++ b/src/hypervisor/domain_driver.h
> @@ -84,6 +84,7 @@ typedef struct _virDomainDriverAutoStartConfig {
>      char *stateDir;
>      virDomainDriverAutoStartCallback callback;
>      void *opaque;
> +    int delayMS; /* milliseconds between starting each guest */

As negative delay doesn't make sense consider declaring this as
unsigned.

Reviewed-by: Peter Krempa <pkrempa@redhat.com>

On Thu, Jan 30, 2025 at 01:12:15PM +0100, Peter Krempa wrote:
> On Wed, Jan 08, 2025 at 19:42:38 +0000, Daniel P. Berrangé wrote:
> > This delay can reduce the CPU/IO load storm when autostarting many
> > guests.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  src/hypervisor/domain_driver.c | 20 +++++++++++++++++---
> >  src/hypervisor/domain_driver.h |  1 +
> >  2 files changed, 18 insertions(+), 3 deletions(-)
> 
> [...]
> 
> > diff --git a/src/hypervisor/domain_driver.h b/src/hypervisor/domain_driver.h
> > index c27ed9155e..d695e26f90 100644
> > --- a/src/hypervisor/domain_driver.h
> > +++ b/src/hypervisor/domain_driver.h
> > @@ -84,6 +84,7 @@ typedef struct _virDomainDriverAutoStartConfig {
> >      char *stateDir;
> >      virDomainDriverAutoStartCallback callback;
> >      void *opaque;
> > +    int delayMS; /* milliseconds between starting each guest */
> 
> As negative delay doesn't make sense consider declaring this as
> unsigned.

Yep, makes sense.

With regards,
Daniel
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