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[Qemu-devel] [PATCH 23/42] migration: yay, buffering is gone
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 23/42] migration: yay, buffering is gone |
Date: |
Fri, 22 Feb 2013 17:36:29 +0100 |
Buffering was needed because blocking writes could take a long time
and starve other threads seeking to grab the big QEMU mutex.
Now that all writes (except within _complete callbacks) are done
outside the big QEMU mutex, we do not need buffering at all.
Reviewed-by: Orit Wasserman <address@hidden>
Reviewed-by: Juan Quintela <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
include/migration/migration.h | 3 --
migration.c | 79 ++++++++++++-------------------------------
savevm.c | 1 +
3 files changed, 22 insertions(+), 61 deletions(-)
diff --git a/include/migration/migration.h b/include/migration/migration.h
index ed20bed..cec8643 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -34,9 +34,6 @@ struct MigrationState
int64_t bandwidth_limit;
size_t bytes_xfer;
size_t xfer_limit;
- uint8_t *buffer;
- size_t buffer_size;
- size_t buffer_capacity;
QemuThread thread;
QEMUBH *cleanup_bh;
diff --git a/migration.c b/migration.c
index e64c92d..4c8d576 100644
--- a/migration.c
+++ b/migration.c
@@ -514,73 +514,41 @@ int64_t migrate_xbzrle_cache_size(void)
/* migration thread support */
-
-static void buffered_flush(MigrationState *s)
-{
- size_t offset = 0;
- ssize_t ret = 0;
-
- DPRINTF("flushing %zu byte(s) of data\n", s->buffer_size);
-
- if (qemu_file_get_error(s->file)) {
- s->buffer_size = 0;
- return;
- }
- qemu_fflush(s->file);
-
- while (s->bytes_xfer < s->xfer_limit && offset < s->buffer_size) {
- size_t to_send = MIN(s->buffer_size - offset, s->xfer_limit -
s->bytes_xfer);
- ret = migrate_fd_put_buffer(s, s->buffer + offset, to_send);
- if (ret <= 0) {
- DPRINTF("error flushing data, %zd\n", ret);
- break;
- } else {
- DPRINTF("flushed %zd byte(s)\n", ret);
- offset += ret;
- s->bytes_xfer += ret;
- }
- }
-
- DPRINTF("flushed %zu of %zu byte(s)\n", offset, s->buffer_size);
- memmove(s->buffer, s->buffer + offset, s->buffer_size - offset);
- s->buffer_size -= offset;
-
- if (ret < 0) {
- qemu_file_set_error(s->file, ret);
- }
-}
-
static int buffered_put_buffer(void *opaque, const uint8_t *buf,
int64_t pos, int size)
{
MigrationState *s = opaque;
- ssize_t error;
+ ssize_t ret;
+ size_t sent;
DPRINTF("putting %d bytes at %" PRId64 "\n", size, pos);
- error = qemu_file_get_error(s->file);
- if (error) {
- DPRINTF("flush when error, bailing: %s\n", strerror(-error));
- return error;
+ ret = qemu_file_get_error(s->file);
+ if (ret) {
+ DPRINTF("flush when error, bailing: %s\n", strerror(-ret));
+ return ret;
}
if (size <= 0) {
return size;
}
- if (size > (s->buffer_capacity - s->buffer_size)) {
- DPRINTF("increasing buffer capacity from %zu by %zu\n",
- s->buffer_capacity, size + 1024);
-
- s->buffer_capacity += size + 1024;
-
- s->buffer = g_realloc(s->buffer, s->buffer_capacity);
+ sent = 0;
+ while (size) {
+ ret = migrate_fd_put_buffer(s, buf, size);
+ if (ret <= 0) {
+ DPRINTF("error flushing data, %zd\n", ret);
+ return ret;
+ } else {
+ DPRINTF("flushed %zd byte(s)\n", ret);
+ sent += ret;
+ buf += ret;
+ size -= ret;
+ s->bytes_xfer += ret;
+ }
}
- memcpy(s->buffer + s->buffer_size, buf, size);
- s->buffer_size += size;
-
- return size;
+ return sent;
}
static int buffered_close(void *opaque)
@@ -712,10 +680,9 @@ static void *buffered_file_thread(void *opaque)
g_usleep((initial_time + BUFFER_DELAY - current_time)*1000);
sleep_time += qemu_get_clock_ms(rt_clock) - current_time;
}
- buffered_flush(s);
if (qemu_file_get_error(s->file)) {
migrate_finish_set_state(s, MIG_STATE_ERROR);
- } else if (last_round && s->buffer_size == 0) {
+ } else if (last_round) {
migrate_finish_set_state(s, MIG_STATE_COMPLETED);
}
}
@@ -735,7 +702,6 @@ static void *buffered_file_thread(void *opaque)
qemu_bh_schedule(s->cleanup_bh);
qemu_mutex_unlock_iothread();
- g_free(s->buffer);
return NULL;
}
@@ -754,9 +720,6 @@ void migrate_fd_connect(MigrationState *s)
trace_migrate_set_state(MIG_STATE_ACTIVE);
s->bytes_xfer = 0;
- s->buffer = NULL;
- s->buffer_size = 0;
- s->buffer_capacity = 0;
/* This is a best 1st approximation. ns to ms */
s->expected_downtime = max_downtime/1000000;
diff --git a/savevm.c b/savevm.c
index 7c7774e..ce10295 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1724,6 +1724,7 @@ void qemu_savevm_state_complete(QEMUFile *f)
}
qemu_put_byte(f, QEMU_VM_EOF);
+ qemu_fflush(f);
}
uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size)
--
1.8.1.2
- [Qemu-devel] [PATCH 02/42] migration: always use vm_stop_force_state, (continued)
- [Qemu-devel] [PATCH 02/42] migration: always use vm_stop_force_state, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 08/42] qemu-file: temporarily expose qemu_file_set_error and qemu_fflush, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 03/42] migration: move more error handling to migrate_fd_cleanup, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 11/42] migration: simplify error handling, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 09/42] migration: flush all data to fd when buffered_flush is called, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 18/42] block-migration: document usage of state across threads, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 20/42] migration: reorder SaveVMHandlers members, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 22/42] migration: run setup callbacks out of big lock, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 21/42] migration: run pending/iterate callbacks out of big lock, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 24/42] Rename buffered_ to migration_, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 23/42] migration: yay, buffering is gone,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 25/42] qemu-file: make qemu_fflush and qemu_file_set_error private again, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 27/42] migration: detect error before sleeping, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 28/42] migration: remove useless qemu_file_get_error check, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 26/42] migration: eliminate last_round, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 39/42] migration: move rate limiting to QEMUFile, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 40/42] migration: move contents of migration_close to migrate_fd_cleanup, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 42/42] migration: inline migrate_fd_close, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 41/42] migration: eliminate s->migration_file, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 15/42] migration: cleanup migration (including thread) in the iothread, Paolo Bonzini, 2013/02/22
- [Qemu-devel] [PATCH 31/42] qemu-file: fsync a writable stdio QEMUFile, Paolo Bonzini, 2013/02/22