This patch adds an API to clear bits corresponding to guest free pages
from the dirty bitmap. Spilt the free page block if it crosses the QEMU
RAMBlock boundary.
Signed-off-by: Wei Wang <wei.w.w...@intel.com>
CC: Dr. David Alan Gilbert <dgilb...@redhat.com>
CC: Juan Quintela <quint...@redhat.com>
CC: Michael S. Tsirkin <m...@redhat.com>
---
include/migration/misc.h | 2 ++
migration/ram.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)
diff --git a/include/migration/misc.h b/include/migration/misc.h
index 4ebf24c..113320e 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -14,11 +14,13 @@
#ifndef MIGRATION_MISC_H
#define MIGRATION_MISC_H
+#include "exec/cpu-common.h"
#include "qemu/notify.h"
/* migration/ram.c */
void ram_mig_init(void);
+void qemu_guest_free_page_hint(void *addr, size_t len);
/* migration/block.c */
diff --git a/migration/ram.c b/migration/ram.c
index 9a72b1a..0147548 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2198,6 +2198,50 @@ static int ram_init_all(RAMState **rsp)
}
/*
+ * This function clears bits of the free pages reported by the caller from the
+ * migration dirty bitmap. @addr is the host address corresponding to the
+ * start of the continuous guest free pages, and @len is the total bytes of
+ * those pages.
+ */
+void qemu_guest_free_page_hint(void *addr, size_t len)
+{
+ RAMBlock *block;
+ ram_addr_t offset;
+ size_t used_len, start, npages;
+
+ for (; len > 0; len -= used_len) {
+ block = qemu_ram_block_from_host(addr, false, &offset);
+ if (unlikely(!block)) {
+ return;
+ }
+
+ /*
+ * This handles the case that the RAMBlock is resized after the free
+ * page hint is reported.
+ */
+ if (unlikely(offset > block->used_length)) {
+ return;
+ }
+
+ if (len <= block->used_length - offset) {
+ used_len = len;
+ } else {
+ used_len = block->used_length - offset;
+ addr += used_len;
+ }
+
+ start = offset >> TARGET_PAGE_BITS;
+ npages = used_len >> TARGET_PAGE_BITS;
+
+ qemu_mutex_lock(&ram_state->bitmap_mutex);
+ ram_state->migration_dirty_pages -=
+ bitmap_count_one_with_offset(block->bmap, start, npages);
+ bitmap_clear(block->bmap, start, npages);
+ qemu_mutex_unlock(&ram_state->bitmap_mutex);
+ }
+}
+
+/*
* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
* long-running RCU critical section. When rcu-reclaims in the code
* start to become numerous it will be necessary to reduce the
--
1.8.3.1
