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migration: Add postcopy_has_request() 

Add a helper to detect whether postcopy has pending request.

Since at it, cleanup the code a bit, e.g. in unqueue_page() we shouldn't need
to check it again on queue empty because we're the only one (besides cleanup
code, which should never run during this process) that will take a request off
the list, so the request list can only grow but not shrink under the hood.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Peter Xu 2022-01-19 16:09:18 +08:00 committed by Juan Quintela
parent 2d1c37c603
commit a1fe28df75
1 changed files with 27 additions and 16 deletions
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23
migration/ram.c
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@ -355,6 +355,12 @@ static RAMState *ram_state;
static NotifierWithReturnList precopy_notifier_list; static NotifierWithReturnList precopy_notifier_list;
/* Whether postcopy has queued requests? */
static bool postcopy_has_request(RAMState *rs)
{
return !QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests);
}
void precopy_infrastructure_init(void) void precopy_infrastructure_init(void)
{ {
notifier_with_return_list_init(&precopy_notifier_list); notifier_with_return_list_init(&precopy_notifier_list);
@ -1539,16 +1545,22 @@ static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss, bool *again)
*/ */
static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset) static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset)
{ {
struct RAMSrcPageRequest *entry;
RAMBlock *block = NULL; RAMBlock *block = NULL;
if (QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests)) { if (!postcopy_has_request(rs)) {
return NULL; return NULL;
} }
QEMU_LOCK_GUARD(&rs->src_page_req_mutex); QEMU_LOCK_GUARD(&rs->src_page_req_mutex);
if (!QSIMPLEQ_EMPTY(&rs->src_page_requests)) {
struct RAMSrcPageRequest *entry = /*
QSIMPLEQ_FIRST(&rs->src_page_requests); * This should _never_ change even after we take the lock, because no one
* should be taking anything off the request list other than us.
*/
assert(postcopy_has_request(rs));
entry = QSIMPLEQ_FIRST(&rs->src_page_requests);
block = entry->rb; block = entry->rb;
*offset = entry->offset; *offset = entry->offset;
@ -1561,7 +1573,6 @@ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset)
g_free(entry); g_free(entry);
migration_consume_urgent_request(); migration_consume_urgent_request();
} }
}
return block; return block;
} }
@ -2992,7 +3003,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
i = 0; i = 0;
while ((ret = qemu_file_rate_limit(f)) == 0 || while ((ret = qemu_file_rate_limit(f)) == 0 ||
!QSIMPLEQ_EMPTY(&rs->src_page_requests)) { postcopy_has_request(rs)) {
int pages; int pages;
if (qemu_file_get_error(f)) { if (qemu_file_get_error(f)) {