next_packet_size name is a bit misleading, so add more comments
where its defined.
We send data in two chunks in multifd thread:
- send the packet with normal (non-zero) guest pages offsets that are
dirty.
This uses the packet_len and we increment number of packets
for this thread that are sent;
- send the normal (non-zero) guest dirty pages themselves in iovs.
The total size of the data pointed by all iovs for this chunk
is next_packet_size. We do not increment the packet_num for this
thread when sending actual pages;
When compression is enabled, next_packet_size is used to indicate
the size of the compressed buffer on source and destination.
Will be it helpful to rename it as data_size or dirty_data_size?
Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
---
migration/multifd.h | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
diff --git a/migration/multifd.h b/migration/multifd.h
index a835643b48..37da9b68c2 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -45,7 +45,13 @@ typedef struct {
uint32_t pages_alloc;
/* non zero pages */
uint32_t normal_pages;
- /* size of the next packet that contains pages */
+ /*
+ * amount of data to be sent to the destination
+ * that is calculated as
+ * - number of the normal guest dirty pages * page_size in non
+ * compression case;
+ * - equals of the compressed data size to be received;
+ */
uint32_t next_packet_size;
uint64_t packet_num;
uint64_t unused[4]; /* Reserved for future use */
@@ -79,11 +85,18 @@ typedef struct {
QIOChannel *c;
/* is the yank function registered */
bool registered_yank;
- /* packet allocated len */
+ /*
+ * allocated length of a packet to be transferred.
+ * It has a size of MultiFDPacket struct plus
+ * the size of the array of guest page offsets (page_count * page_size).
+ */
uint32_t packet_len;
/* guest page size */
uint32_t page_size;
- /* number of pages in a full packet */
+ /*
+ * maximum number of dirty pages in a full packet calculated as
+ * MULTIFD_PACKET_SIZE / qemu_target_page_size()
+ */
uint32_t page_count;
/* multifd flags for sending ram */
int write_flags;
@@ -116,7 +129,13 @@ typedef struct {
/* pointer to the packet */
MultiFDPacket_t *packet;
- /* size of the next packet that contains pages */
+ /*
+ * amount of data to be sent to the destination
+ * that is calculated as
+ * - number of the normal guest dirty pages * page_size in non
+ * compression case;
+ * - equals of the compressed data size to be received;
+ */
uint32_t next_packet_size;
/* packets sent through this channel */
uint64_t num_packets;
@@ -171,7 +190,13 @@ typedef struct {
/* pointer to the packet */
MultiFDPacket_t *packet;
- /* size of the next packet that contains pages */
+ /*
+ * amount of data to be received by the destination
+ * that is calculated as
+ * - number of the normal guest dirty pages * page_size in non
+ * compression case;
+ * - equals of the compressed data size to be received;
+ */
uint32_t next_packet_size;
/* packets sent through this channel */
uint64_t num_packets;
--
2.34.1
