[PATCH 10/16] migration/multifd: Enable DSA offloading in multifd sender path.

[Hao Xiang <hao.xiang@bytedance.com>]

Multifd sender path gets an array of pages queued by the migration
thread. It performs zero page checking on every page in the array.
The pages are classfied as either a zero page or a normal page. This
change uses Intel DSA to offload the zero page checking from CPU to
the DSA accelerator. The sender thread submits a batch of pages to DSA
hardware and waits for the DSA completion thread to signal for work
completion.

Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
---
 migration/multifd.c | 101 +++++++++++++++++++++++++++++++++++++-------
 migration/multifd.h |   3 ++
 2 files changed, 89 insertions(+), 15 deletions(-)

diff --git a/migration/multifd.c b/migration/multifd.c
index 452fb158b8..79fecbd3ae 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -13,6 +13,8 @@
 #include "qemu/osdep.h"
 #include "qemu/rcu.h"
 #include "qemu/cutils.h"
+#include "qemu/dsa.h"
+#include "qemu/memalign.h"
 #include "exec/target_page.h"
 #include "sysemu/sysemu.h"
 #include "exec/ramblock.h"
@@ -555,6 +557,8 @@ void multifd_save_cleanup(void)
             qemu_thread_join(&p->thread);
         }
     }
+    dsa_stop();
+    dsa_cleanup();
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDSendParams *p = &multifd_send_state->params[i];
         Error *local_err = NULL;
@@ -571,6 +575,11 @@ void multifd_save_cleanup(void)
         p->name = NULL;
         multifd_pages_clear(p->pages);
         p->pages = NULL;
+        g_free(p->addr);
+        p->addr = NULL;
+        buffer_zero_batch_task_destroy(p->dsa_batch_task);
+        qemu_vfree(p->dsa_batch_task);
+        p->dsa_batch_task = NULL;
         p->packet_len = 0;
         g_free(p->packet);
         p->packet = NULL;
@@ -675,13 +684,71 @@ int multifd_send_sync_main(QEMUFile *f)
     return 0;
 }
 
+static void set_page(MultiFDSendParams *p, bool zero_page, uint64_t offset)
+{
+    RAMBlock *rb = p->pages->block;
+    if (zero_page) {
+        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++;
+    }
+}
+
+static void buffer_is_zero_use_cpu(MultiFDSendParams *p)
+{
+    const void **buf = (const void **)p->addr;
+    assert(!migrate_use_main_zero_page());
+    assert(!dsa_is_running());
+
+    for (int i = 0; i < p->pages->num; i++) {
+        p->dsa_batch_task->results[i] = buffer_is_zero(buf[i], p->page_size);
+    }
+}
+
+static void buffer_is_zero_use_dsa(MultiFDSendParams *p)
+{
+    assert(!migrate_use_main_zero_page());
+    assert(dsa_is_running());
+
+    buffer_is_zero_dsa_batch_async(p->dsa_batch_task,
+                                   (const void **)p->addr,
+                                   p->pages->num,
+                                   p->page_size);
+}
+
+static void multifd_zero_page_check(MultiFDSendParams *p)
+{
+    /* older qemu don't understand zero page on multifd channel */
+    bool use_multifd_zero_page = !migrate_use_main_zero_page();
+    bool use_multifd_dsa_accel = dsa_is_running();
+
+    RAMBlock *rb = p->pages->block;
+
+    for (int i = 0; i < p->pages->num; i++) {
+        p->addr[i] = (ram_addr_t)(rb->host + p->pages->offset[i]);
+    }
+
+    if (!use_multifd_zero_page || !use_multifd_dsa_accel) {
+        buffer_is_zero_use_cpu(p);
+    } else {
+        buffer_is_zero_use_dsa(p);
+    }
+
+    for (int i = 0; i < p->pages->num; i++) {
+        uint64_t offset = p->pages->offset[i];
+        bool zero_page = p->dsa_batch_task->results[i];
+        set_page(p, zero_page, offset);
+    }
+}
+
 static void *multifd_send_thread(void *opaque)
 {
     MultiFDSendParams *p = opaque;
     MigrationThread *thread = NULL;
     Error *local_err = NULL;
-    /* older qemu don't understand zero page on multifd channel */
-    bool use_multifd_zero_page = !migrate_use_main_zero_page();
     int ret = 0;
     bool use_zero_copy_send = migrate_zero_copy_send();
 
@@ -707,7 +774,6 @@ 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) {
@@ -725,18 +791,7 @@ static void *multifd_send_thread(void *opaque)
                 p->iovs_num = 1;
             }
 
-            for (int i = 0; i < p->pages->num; i++) {
-                uint64_t offset = p->pages->offset[i];
-                if (use_multifd_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++;
-                }
-            }
+            multifd_zero_page_check(p);
 
             if (p->normal_num) {
                 ret = multifd_send_state->ops->send_prepare(p, &local_err);
@@ -958,11 +1013,15 @@ int multifd_save_setup(Error **errp)
     int thread_count;
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     uint8_t i;
+    const char *dsa_parameter = migrate_multifd_dsa_accel();
 
     if (!migrate_multifd()) {
         return 0;
     }
 
+    dsa_init(dsa_parameter);
+    dsa_start();
+
     thread_count = migrate_multifd_channels();
     multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
     multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
@@ -981,6 +1040,10 @@ int multifd_save_setup(Error **errp)
         p->pending_job = 0;
         p->id = i;
         p->pages = multifd_pages_init(page_count);
+        p->addr = g_new0(ram_addr_t, page_count);
+        p->dsa_batch_task = 
+            (struct buffer_zero_batch_task *)qemu_memalign(64, sizeof(*p->dsa_batch_task));
+        buffer_zero_batch_task_init(p->dsa_batch_task, page_count);
         p->packet_len = sizeof(MultiFDPacket_t)
                       + sizeof(uint64_t) * page_count;
         p->packet = g_malloc0(p->packet_len);
@@ -1014,6 +1077,7 @@ int multifd_save_setup(Error **errp)
             return ret;
         }
     }
+
     return 0;
 }
 
@@ -1091,6 +1155,8 @@ void multifd_load_cleanup(void)
 
         qemu_thread_join(&p->thread);
     }
+    dsa_stop();
+    dsa_cleanup();
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDRecvParams *p = &multifd_recv_state->params[i];
 
@@ -1225,6 +1291,7 @@ int multifd_load_setup(Error **errp)
     int thread_count;
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     uint8_t i;
+    const char *dsa_parameter = migrate_multifd_dsa_accel();
 
     /*
      * Return successfully if multiFD recv state is already initialised
@@ -1234,6 +1301,9 @@ int multifd_load_setup(Error **errp)
         return 0;
     }
 
+    dsa_init(dsa_parameter);
+    dsa_start();
+
     thread_count = migrate_multifd_channels();
     multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
     multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
@@ -1270,6 +1340,7 @@ int multifd_load_setup(Error **errp)
             return ret;
         }
     }
+
     return 0;
 }
 
diff --git a/migration/multifd.h b/migration/multifd.h
index e8f90776bb..297b055e2b 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -114,6 +114,9 @@ typedef struct {
      * pending_job != 0 -> multifd_channel can use it.
      */
     MultiFDPages_t *pages;
+    /* Address of each pages in pages */
+    ram_addr_t *addr;
+    struct buffer_zero_batch_task *dsa_batch_task;
 
     /* thread local variables. No locking required */
 
-- 
2.30.2