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[PATCH v6 12/13] multifd: Zero pages transmission
From: |
Juan Quintela |
Subject: |
[PATCH v6 12/13] multifd: Zero pages transmission |
Date: |
Wed, 11 May 2022 00:42:19 +0200 |
This implements the zero page dection and handling.
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
Add comment for offset (dave)
Use local variables for offset/block to have shorter lines
---
migration/multifd.h | 5 +++++
migration/multifd.c | 41 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 44 insertions(+), 2 deletions(-)
diff --git a/migration/multifd.h b/migration/multifd.h
index 3bb33eb4af..b885390116 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -52,6 +52,11 @@ typedef struct {
uint32_t unused32[1]; /* Reserved for future use */
uint64_t unused64[3]; /* Reserved for future use */
char ramblock[256];
+ /*
+ * This array contains the pointers to:
+ * - normal pages (initial normal_pages entries)
+ * - zero pages (following zero_pages entries)
+ */
uint64_t offset[];
} __attribute__((packed)) MultiFDPacket_t;
diff --git a/migration/multifd.c b/migration/multifd.c
index 15a16686db..aa012634cf 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -11,6 +11,7 @@
*/
#include "qemu/osdep.h"
+#include "qemu/cutils.h"
#include "qemu/rcu.h"
#include "exec/target_page.h"
#include "sysemu/sysemu.h"
@@ -275,6 +276,12 @@ static void multifd_send_fill_packet(MultiFDSendParams *p)
packet->offset[i] = cpu_to_be64(temp);
}
+ for (i = 0; i < p->zero_num; i++) {
+ /* there are architectures where ram_addr_t is 32 bit */
+ uint64_t temp = p->zero[i];
+
+ packet->offset[p->normal_num + i] = cpu_to_be64(temp);
+ }
}
static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
@@ -358,6 +365,18 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams
*p, Error **errp)
p->normal[i] = offset;
}
+ for (i = 0; i < p->zero_num; i++) {
+ uint64_t offset = be64_to_cpu(packet->offset[p->normal_num + i]);
+
+ if (offset > (block->used_length - p->page_size)) {
+ error_setg(errp, "multifd: offset too long %" PRIu64
+ " (max " RAM_ADDR_FMT ")",
+ offset, block->used_length);
+ return -1;
+ }
+ p->zero[i] = offset;
+ }
+
return 0;
}
@@ -618,6 +637,8 @@ static void *multifd_send_thread(void *opaque)
{
MultiFDSendParams *p = opaque;
Error *local_err = NULL;
+ /* qemu older than 7.0 don't understand zero page on multifd channel */
+ bool use_zero_page = migrate_use_multifd_zero_page();
int ret = 0;
trace_multifd_send_thread_start(p->id);
@@ -639,6 +660,7 @@ static void *multifd_send_thread(void *opaque)
qemu_mutex_lock(&p->mutex);
if (p->pending_job) {
+ RAMBlock *rb = p->pages->block;
uint64_t packet_num = p->packet_num;
p->flags = 0;
if (p->sync_needed) {
@@ -652,8 +674,16 @@ static void *multifd_send_thread(void *opaque)
p->zero_num = 0;
for (int i = 0; i < p->pages->num; i++) {
- p->normal[p->normal_num] = p->pages->offset[i];
- p->normal_num++;
+ uint64_t offset = p->pages->offset[i];
+ if (use_zero_page &&
+ buffer_is_zero(rb->host + offset, p->page_size)) {
+ p->zero[p->zero_num] = offset;
+ p->zero_num++;
+ ram_release_page(rb->idstr, offset);
+ } else {
+ p->normal[p->normal_num] = offset;
+ p->normal_num++;
+ }
}
if (p->normal_num) {
@@ -1104,6 +1134,13 @@ static void *multifd_recv_thread(void *opaque)
}
}
+ for (int i = 0; i < p->zero_num; i++) {
+ void *page = p->host + p->zero[i];
+ if (!buffer_is_zero(page, p->page_size)) {
+ memset(page, 0, p->page_size);
+ }
+ }
+
if (sync_needed) {
qemu_sem_post(&multifd_recv_state->sem_sync);
qemu_sem_wait(&p->sem_sync);
--
2.35.1
- [PATCH v6 04/13] migration: Export ram_transferred_ram(), (continued)
- [PATCH v6 04/13] migration: Export ram_transferred_ram(), Juan Quintela, 2022/05/10
- [PATCH v6 08/13] multifd: Prepare to send a packet without the mutex held, Juan Quintela, 2022/05/10
- [PATCH v6 09/13] multifd: Add property to enable/disable zero_page, Juan Quintela, 2022/05/10
- [PATCH v6 10/13] migration: Export ram_release_page(), Juan Quintela, 2022/05/10
- [PATCH v6 06/13] migration: Make ram_save_target_page() a pointer, Juan Quintela, 2022/05/10
- [PATCH v6 11/13] multifd: Support for zero pages transmission, Juan Quintela, 2022/05/10
- [PATCH v6 02/13] multifd: Create page_size fields into both MultiFD{Recv, Send}Params, Juan Quintela, 2022/05/10
- [PATCH v6 13/13] migration: Use multifd before we check for the zero page, Juan Quintela, 2022/05/10
- [PATCH v6 12/13] multifd: Zero pages transmission,
Juan Quintela <=
- [PATCH v6 07/13] multifd: Make flags field thread local, Juan Quintela, 2022/05/10
- Re: [PATCH v6 00/13] Migration: Transmit and detect zero pages in the multifd threads, Dr. David Alan Gilbert, 2022/05/12