| Message ID | 20220119080929.39485-10-peterx@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | migration: Postcopy Preemption | expand |
* Peter Xu (peterx@redhat.com) wrote: > Postcopy create threads. A common manner is we init a sem and use it to sync > with the thread. Namely, we have fault_thread_sem and listen_thread_sem and > they're only used for this. > > Make it a shared infrastructure so it's easier to create yet another thread. > It might be worth a note saying you now share that sem, so you can't start two threads in parallel. Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > migration/migration.h | 5 ++--- > migration/postcopy-ram.c | 19 +++++++++++++------ > migration/postcopy-ram.h | 4 ++++ > migration/savevm.c | 12 +++--------- > 4 files changed, 22 insertions(+), 18 deletions(-) > > diff --git a/migration/migration.h b/migration/migration.h > index 8bb2931312..35e7f7babe 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -70,7 +70,8 @@ struct MigrationIncomingState { > /* A hook to allow cleanup at the end of incoming migration */ > void *transport_data; > void (*transport_cleanup)(void *data); > - > + /* Used to sync thread creations */ > + QemuSemaphore thread_sync_sem; > /* > * Free at the start of the main state load, set as the main thread finishes > * loading state. > @@ -83,13 +84,11 @@ struct MigrationIncomingState { > size_t largest_page_size; > bool have_fault_thread; > QemuThread fault_thread; > - QemuSemaphore fault_thread_sem; > /* Set this when we want the fault thread to quit */ > bool fault_thread_quit; > > bool have_listen_thread; > QemuThread listen_thread; > - QemuSemaphore listen_thread_sem; > > /* For the kernel to send us notifications */ > int userfault_fd; > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index d78e1b9373..88c832eeba 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -77,6 +77,16 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) > &pnd); > } > > +void postcopy_thread_create(MigrationIncomingState *mis, > + QemuThread *thread, const char *name, > + void *(*fn)(void *), int joinable) > +{ > + qemu_sem_init(&mis->thread_sync_sem, 0); > + qemu_thread_create(thread, name, fn, mis, joinable); > + qemu_sem_wait(&mis->thread_sync_sem); > + qemu_sem_destroy(&mis->thread_sync_sem); > +} > + > /* Postcopy needs to detect accesses to pages that haven't yet been copied > * across, and efficiently map new pages in, the techniques for doing this > * are target OS specific. > @@ -901,7 +911,7 @@ static void *postcopy_ram_fault_thread(void *opaque) > trace_postcopy_ram_fault_thread_entry(); > rcu_register_thread(); > mis->last_rb = NULL; /* last RAMBlock we sent part of */ > - qemu_sem_post(&mis->fault_thread_sem); > + qemu_sem_post(&mis->thread_sync_sem); > > struct pollfd *pfd; > size_t pfd_len = 2 + mis->postcopy_remote_fds->len; > @@ -1172,11 +1182,8 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis) > return -1; > } > > - qemu_sem_init(&mis->fault_thread_sem, 0); > - qemu_thread_create(&mis->fault_thread, "postcopy/fault", > - postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE); > - qemu_sem_wait(&mis->fault_thread_sem); > - qemu_sem_destroy(&mis->fault_thread_sem); > + postcopy_thread_create(mis, &mis->fault_thread, "postcopy/fault", > + postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE); > mis->have_fault_thread = true; > > /* Mark so that we get notified of accesses to unwritten areas */ > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h > index 6d2b3cf124..07684c0e1d 100644 > --- a/migration/postcopy-ram.h > +++ b/migration/postcopy-ram.h > @@ -135,6 +135,10 @@ void postcopy_remove_notifier(NotifierWithReturn *n); > /* Call the notifier list set by postcopy_add_start_notifier */ > int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp); > > +void postcopy_thread_create(MigrationIncomingState *mis, > + QemuThread *thread, const char *name, > + void *(*fn)(void *), int joinable); > + > struct PostCopyFD; > > /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */ > diff --git a/migration/savevm.c b/migration/savevm.c > index 3b8f565b14..3342b74c24 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -1862,7 +1862,7 @@ static void *postcopy_ram_listen_thread(void *opaque) > > migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, > MIGRATION_STATUS_POSTCOPY_ACTIVE); > - qemu_sem_post(&mis->listen_thread_sem); > + qemu_sem_post(&mis->thread_sync_sem); > trace_postcopy_ram_listen_thread_start(); > > rcu_register_thread(); > @@ -1987,14 +1987,8 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis) > } > > mis->have_listen_thread = true; > - /* Start up the listening thread and wait for it to signal ready */ > - qemu_sem_init(&mis->listen_thread_sem, 0); > - qemu_thread_create(&mis->listen_thread, "postcopy/listen", > - postcopy_ram_listen_thread, NULL, > - QEMU_THREAD_DETACHED); > - qemu_sem_wait(&mis->listen_thread_sem); > - qemu_sem_destroy(&mis->listen_thread_sem); > - > + postcopy_thread_create(mis, &mis->listen_thread, "postcopy/listen", > + postcopy_ram_listen_thread, QEMU_THREAD_DETACHED); > trace_loadvm_postcopy_handle_listen("return"); > > return 0; > -- > 2.32.0 >
On Thu, Feb 03, 2022 at 03:19:48PM +0000, Dr. David Alan Gilbert wrote: > * Peter Xu (peterx@redhat.com) wrote: > > Postcopy create threads. A common manner is we init a sem and use it to sync > > with the thread. Namely, we have fault_thread_sem and listen_thread_sem and > > they're only used for this. > > > > Make it a shared infrastructure so it's easier to create yet another thread. > > > > It might be worth a note saying you now share that sem, so you can't > start two threads in parallel. I'll squash this into the patch: ---8<--- diff --git a/migration/migration.h b/migration/migration.h index 845be3463c..2a311fd8d6 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -72,7 +72,10 @@ struct MigrationIncomingState { /* A hook to allow cleanup at the end of incoming migration */ void *transport_data; void (*transport_cleanup)(void *data); - /* Used to sync thread creations */ + /* + * Used to sync thread creations. Note that we can't create threads in + * parallel with this sem. + */ QemuSemaphore thread_sync_sem; /* * Free at the start of the main state load, set as the main thread finishes diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 099d8ed478..1a3ba1db84 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -79,6 +79,10 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) &pnd); } +/* + * NOTE: this routine is not thread safe, we can't call it concurrently. But it + * should be good enough for migration's purposes. + */ void postcopy_thread_create(MigrationIncomingState *mis, QemuThread *thread, const char *name, void *(*fn)(void *), int joinable) ---8<--- > > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Thanks,
* Peter Xu (peterx@redhat.com) wrote: > On Thu, Feb 03, 2022 at 03:19:48PM +0000, Dr. David Alan Gilbert wrote: > > * Peter Xu (peterx@redhat.com) wrote: > > > Postcopy create threads. A common manner is we init a sem and use it to sync > > > with the thread. Namely, we have fault_thread_sem and listen_thread_sem and > > > they're only used for this. > > > > > > Make it a shared infrastructure so it's easier to create yet another thread. > > > > > > > It might be worth a note saying you now share that sem, so you can't > > start two threads in parallel. > > I'll squash this into the patch: Thanks > ---8<--- > diff --git a/migration/migration.h b/migration/migration.h > index 845be3463c..2a311fd8d6 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -72,7 +72,10 @@ struct MigrationIncomingState { > /* A hook to allow cleanup at the end of incoming migration */ > void *transport_data; > void (*transport_cleanup)(void *data); > - /* Used to sync thread creations */ > + /* > + * Used to sync thread creations. Note that we can't create threads in > + * parallel with this sem. > + */ > QemuSemaphore thread_sync_sem; > /* > * Free at the start of the main state load, set as the main thread finishes > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index 099d8ed478..1a3ba1db84 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -79,6 +79,10 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) > &pnd); > } > > +/* > + * NOTE: this routine is not thread safe, we can't call it concurrently. But it > + * should be good enough for migration's purposes. > + */ > void postcopy_thread_create(MigrationIncomingState *mis, > QemuThread *thread, const char *name, > void *(*fn)(void *), int joinable) > ---8<--- > > > > > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > > Thanks, > > -- > Peter Xu >
diff --git a/migration/migration.h b/migration/migration.h index 8bb2931312..35e7f7babe 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -70,7 +70,8 @@ struct MigrationIncomingState { /* A hook to allow cleanup at the end of incoming migration */ void *transport_data; void (*transport_cleanup)(void *data); - + /* Used to sync thread creations */ + QemuSemaphore thread_sync_sem; /* * Free at the start of the main state load, set as the main thread finishes * loading state. @@ -83,13 +84,11 @@ struct MigrationIncomingState { size_t largest_page_size; bool have_fault_thread; QemuThread fault_thread; - QemuSemaphore fault_thread_sem; /* Set this when we want the fault thread to quit */ bool fault_thread_quit; bool have_listen_thread; QemuThread listen_thread; - QemuSemaphore listen_thread_sem; /* For the kernel to send us notifications */ int userfault_fd; diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index d78e1b9373..88c832eeba 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -77,6 +77,16 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) &pnd); } +void postcopy_thread_create(MigrationIncomingState *mis, + QemuThread *thread, const char *name, + void *(*fn)(void *), int joinable) +{ + qemu_sem_init(&mis->thread_sync_sem, 0); + qemu_thread_create(thread, name, fn, mis, joinable); + qemu_sem_wait(&mis->thread_sync_sem); + qemu_sem_destroy(&mis->thread_sync_sem); +} + /* Postcopy needs to detect accesses to pages that haven't yet been copied * across, and efficiently map new pages in, the techniques for doing this * are target OS specific. @@ -901,7 +911,7 @@ static void *postcopy_ram_fault_thread(void *opaque) trace_postcopy_ram_fault_thread_entry(); rcu_register_thread(); mis->last_rb = NULL; /* last RAMBlock we sent part of */ - qemu_sem_post(&mis->fault_thread_sem); + qemu_sem_post(&mis->thread_sync_sem); struct pollfd *pfd; size_t pfd_len = 2 + mis->postcopy_remote_fds->len; @@ -1172,11 +1182,8 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis) return -1; } - qemu_sem_init(&mis->fault_thread_sem, 0); - qemu_thread_create(&mis->fault_thread, "postcopy/fault", - postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE); - qemu_sem_wait(&mis->fault_thread_sem); - qemu_sem_destroy(&mis->fault_thread_sem); + postcopy_thread_create(mis, &mis->fault_thread, "postcopy/fault", + postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE); mis->have_fault_thread = true; /* Mark so that we get notified of accesses to unwritten areas */ diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h index 6d2b3cf124..07684c0e1d 100644 --- a/migration/postcopy-ram.h +++ b/migration/postcopy-ram.h @@ -135,6 +135,10 @@ void postcopy_remove_notifier(NotifierWithReturn *n); /* Call the notifier list set by postcopy_add_start_notifier */ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp); +void postcopy_thread_create(MigrationIncomingState *mis, + QemuThread *thread, const char *name, + void *(*fn)(void *), int joinable); + struct PostCopyFD; /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */ diff --git a/migration/savevm.c b/migration/savevm.c index 3b8f565b14..3342b74c24 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1862,7 +1862,7 @@ static void *postcopy_ram_listen_thread(void *opaque) migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, MIGRATION_STATUS_POSTCOPY_ACTIVE); - qemu_sem_post(&mis->listen_thread_sem); + qemu_sem_post(&mis->thread_sync_sem); trace_postcopy_ram_listen_thread_start(); rcu_register_thread(); @@ -1987,14 +1987,8 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis) } mis->have_listen_thread = true; - /* Start up the listening thread and wait for it to signal ready */ - qemu_sem_init(&mis->listen_thread_sem, 0); - qemu_thread_create(&mis->listen_thread, "postcopy/listen", - postcopy_ram_listen_thread, NULL, - QEMU_THREAD_DETACHED); - qemu_sem_wait(&mis->listen_thread_sem); - qemu_sem_destroy(&mis->listen_thread_sem); - + postcopy_thread_create(mis, &mis->listen_thread, "postcopy/listen", + postcopy_ram_listen_thread, QEMU_THREAD_DETACHED); trace_loadvm_postcopy_handle_listen("return"); return 0;
Postcopy create threads. A common manner is we init a sem and use it to sync with the thread. Namely, we have fault_thread_sem and listen_thread_sem and they're only used for this. Make it a shared infrastructure so it's easier to create yet another thread. Signed-off-by: Peter Xu <peterx@redhat.com> --- migration/migration.h | 5 ++--- migration/postcopy-ram.c | 19 +++++++++++++------ migration/postcopy-ram.h | 4 ++++ migration/savevm.c | 12 +++--------- 4 files changed, 22 insertions(+), 18 deletions(-)