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[Qemu-devel] [PATCH v8 06/24] migration: allow fault thread to pause
From: |
Peter Xu |
Subject: |
[Qemu-devel] [PATCH v8 06/24] migration: allow fault thread to pause |
Date: |
Wed, 2 May 2018 18:47:22 +0800 |
Allows the fault thread to stop handling page faults temporarily. When
network failure happened (and if we expect a recovery afterwards), we
should not allow the fault thread to continue sending things to source,
instead, it should halt for a while until the connection is rebuilt.
When the dest main thread noticed the failure, it kicks the fault thread
to switch to pause state.
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
Signed-off-by: Peter Xu <address@hidden>
---
migration/migration.h | 1 +
migration/migration.c | 1 +
migration/postcopy-ram.c | 54 ++++++++++++++++++++++++++++++++++++++++++++----
migration/savevm.c | 3 +++
migration/trace-events | 2 ++
5 files changed, 57 insertions(+), 4 deletions(-)
diff --git a/migration/migration.h b/migration/migration.h
index db28a66a92..83ebc18b1e 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -76,6 +76,7 @@ struct MigrationIncomingState {
/* notify PAUSED postcopy incoming migrations to try to continue */
QemuSemaphore postcopy_pause_sem_dst;
+ QemuSemaphore postcopy_pause_sem_fault;
};
MigrationIncomingState *migration_incoming_get_current(void);
diff --git a/migration/migration.c b/migration/migration.c
index 09dbf5350c..9d184b3f36 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -160,6 +160,7 @@ MigrationIncomingState *migration_incoming_get_current(void)
qemu_mutex_init(&mis_current.rp_mutex);
qemu_event_init(&mis_current.main_thread_load_event, false);
qemu_sem_init(&mis_current.postcopy_pause_sem_dst, 0);
+ qemu_sem_init(&mis_current.postcopy_pause_sem_fault, 0);
init_dirty_bitmap_incoming_migration();
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 8ceeaa2a93..658b750a8e 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -830,6 +830,17 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
affected_cpu);
}
+static bool postcopy_pause_fault_thread(MigrationIncomingState *mis)
+{
+ trace_postcopy_pause_fault_thread();
+
+ qemu_sem_wait(&mis->postcopy_pause_sem_fault);
+
+ trace_postcopy_pause_fault_thread_continued();
+
+ return true;
+}
+
/*
* Handle faults detected by the USERFAULT markings
*/
@@ -880,6 +891,22 @@ static void *postcopy_ram_fault_thread(void *opaque)
break;
}
+ if (!mis->to_src_file) {
+ /*
+ * Possibly someone tells us that the return path is
+ * broken already using the event. We should hold until
+ * the channel is rebuilt.
+ */
+ if (postcopy_pause_fault_thread(mis)) {
+ mis->last_rb = NULL;
+ /* Continue to read the userfaultfd */
+ } else {
+ error_report("%s: paused but don't allow to continue",
+ __func__);
+ break;
+ }
+ }
+
if (pfd[1].revents) {
uint64_t tmp64 = 0;
@@ -942,18 +969,37 @@ static void *postcopy_ram_fault_thread(void *opaque)
(uintptr_t)(msg.arg.pagefault.address),
msg.arg.pagefault.feat.ptid, rb);
+retry:
/*
* Send the request to the source - we want to request one
* of our host page sizes (which is >= TPS)
*/
if (rb != mis->last_rb) {
mis->last_rb = rb;
- migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
- rb_offset, qemu_ram_pagesize(rb));
+ ret = migrate_send_rp_req_pages(mis,
+ qemu_ram_get_idstr(rb),
+ rb_offset,
+ qemu_ram_pagesize(rb));
} else {
/* Save some space */
- migrate_send_rp_req_pages(mis, NULL,
- rb_offset, qemu_ram_pagesize(rb));
+ ret = migrate_send_rp_req_pages(mis,
+ NULL,
+ rb_offset,
+ qemu_ram_pagesize(rb));
+ }
+
+ if (ret) {
+ /* May be network failure, try to wait for recovery */
+ if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
+ /* We got reconnected somehow, try to continue */
+ mis->last_rb = NULL;
+ goto retry;
+ } else {
+ /* This is a unavoidable fault */
+ error_report("%s: migrate_send_rp_req_pages() get %d",
+ __func__, ret);
+ break;
+ }
}
}
diff --git a/migration/savevm.c b/migration/savevm.c
index 8ad99b1eaa..6ee69d8283 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2083,6 +2083,9 @@ static bool
postcopy_pause_incoming(MigrationIncomingState *mis)
mis->to_src_file = NULL;
qemu_mutex_unlock(&mis->rp_mutex);
+ /* Notify the fault thread for the invalidated file handle */
+ postcopy_fault_thread_notify(mis);
+
error_report("Detected IO failure for postcopy. "
"Migration paused.");
diff --git a/migration/trace-events b/migration/trace-events
index cd971bf9fe..7f836499d1 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -101,6 +101,8 @@ open_return_path_on_source_continue(void) ""
postcopy_start(void) ""
postcopy_pause_return_path(void) ""
postcopy_pause_return_path_continued(void) ""
+postcopy_pause_fault_thread(void) ""
+postcopy_pause_fault_thread_continued(void) ""
postcopy_pause_continued(void) ""
postcopy_pause_incoming(void) ""
postcopy_pause_incoming_continued(void) ""
--
2.14.3
- [Qemu-devel] [PATCH v8 00/24] Migration: postcopy failure recovery, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 03/24] migration: implement "postcopy-pause" src logic, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 04/24] migration: allow dst vm pause on postcopy, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 05/24] migration: allow src return path to pause, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 06/24] migration: allow fault thread to pause,
Peter Xu <=
- [Qemu-devel] [PATCH v8 08/24] migration: rebuild channel on source, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 07/24] qmp: hmp: add migrate "resume" option, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 09/24] migration: new state "postcopy-recover", Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 10/24] migration: wakeup dst ram-load-thread for recover, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 11/24] migration: new cmd MIG_CMD_RECV_BITMAP, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 12/24] migration: new message MIG_RP_MSG_RECV_BITMAP, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 13/24] migration: new cmd MIG_CMD_POSTCOPY_RESUME, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 14/24] migration: new message MIG_RP_MSG_RESUME_ACK, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 15/24] migration: introduce SaveVMHandlers.resume_prepare, Peter Xu, 2018/05/02
- [Qemu-devel] [PATCH v8 16/24] migration: synchronize dirty bitmap for resume, Peter Xu, 2018/05/02