qemu-kvm/SOURCES/kvm-multifd-Create-property-multifd-flush-after-each-sec.patch

From 2a5ea92ca0a5dffad54e4d06a683f683996cea9a Mon Sep 17 00:00:00 2001
From: Juan Quintela <quintela@redhat.com>
Date: Tue, 21 Jun 2022 12:13:14 +0200
Subject: [PATCH 05/12] multifd: Create property
 multifd-flush-after-each-section
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RH-Author: quintela1 <quintela@redhat.com>
RH-MergeRequest: 186: Multifd flushes its channels 10 times per second
RH-Bugzilla: 2196295
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: Leonardo Brás <leobras@redhat.com>
RH-Commit: [1/3] 5bf5348e8be5b1d1629b859ce1ddb7aa0d72c0d6 (juan.quintela/c9s-qemu-kvm)

We used to flush all channels at the end of each RAM section
sent.  That is not needed, so preparing to only flush after a full
iteration through all the RAM.

Default value of the property is false.  But we return "true" in
migrate_multifd_flush_after_each_section() until we implement the code
in following patches.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>

---

Rename each-iteration to after-each-section
Rename multifd-sync-after-each-section to
       multifd-flush-after-each-section
Move to machine-8.0 (peter)

conflit hw_compat_8_0 and hw_compat_rhel_9_2

(cherry picked from commit 77c259a4cb1c9799754b48f570301ebf1de5ded8)
---
 hw/core/machine.c     |  2 ++
 migration/migration.h | 12 ++++++++++++
 migration/options.c   | 13 +++++++++++++
 migration/options.h   |  1 +
 4 files changed, 28 insertions(+)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 5abdc8c39b..5ea52317b9 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -54,6 +54,8 @@ const char *rhel_old_machine_deprecation =
     "machine types for previous major releases are deprecated";
 
 GlobalProperty hw_compat_rhel_9_2[] = {
+  /* hw_compat_rhel_9_2 from hw_compat_8_0 */
+  { "migration", "multifd-flush-after-each-section", "on"},
   /* hw_compat_rhel_9_2 from hw_compat_7_2 */
   { "e1000e", "migrate-timadj", "off" },
   /* hw_compat_rhel_9_2 from hw_compat_7_2 */
diff --git a/migration/migration.h b/migration/migration.h
index 7ccf460aa2..04c78c1fd6 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -411,6 +411,18 @@ struct MigrationState {
      */
     bool preempt_pre_7_2;
 
+    /*
+     * flush every channel after each section sent.
+     *
+     * This assures that we can't mix pages from one iteration through
+     * ram pages with pages for the following iteration.  We really
+     * only need to do this flush after we have go through all the
+     * dirty pages.  For historical reasons, we do that after each
+     * section.  This is suboptimal (we flush too many times).
+     * Default value is false.  Setting this property has no effect
+     * until the patch that removes this comment.  (since 8.1)
+     */
+    bool multifd_flush_after_each_section;
     /*
      * This decides the size of guest memory chunk that will be used
      * to track dirty bitmap clearing.  The size of memory chunk will
diff --git a/migration/options.c b/migration/options.c
index ccd7ef3907..5b0d080ecb 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -88,6 +88,8 @@ Property migration_properties[] = {
                      send_section_footer, true),
     DEFINE_PROP_BOOL("decompress-error-check", MigrationState,
                       decompress_error_check, true),
+    DEFINE_PROP_BOOL("multifd-flush-after-each-section", MigrationState,
+                      multifd_flush_after_each_section, true),
     DEFINE_PROP_UINT8("x-clear-bitmap-shift", MigrationState,
                       clear_bitmap_shift, CLEAR_BITMAP_SHIFT_DEFAULT),
     DEFINE_PROP_BOOL("x-preempt-pre-7-2", MigrationState,
@@ -344,6 +346,17 @@ bool migrate_zero_copy_send(void)
 
 /* pseudo capabilities */
 
+bool migrate_multifd_flush_after_each_section(void)
+{
+    MigrationState *s = migrate_get_current();
+
+    /*
+     * Until the patch that remove this comment, we always return that
+     * the property is enabled.
+     */
+    return true || s->multifd_flush_after_each_section;
+}
+
 bool migrate_postcopy(void)
 {
     return migrate_postcopy_ram() || migrate_dirty_bitmaps();
diff --git a/migration/options.h b/migration/options.h
index 0fc7be6869..271f49ae5f 100644
--- a/migration/options.h
+++ b/migration/options.h
@@ -60,6 +60,7 @@ bool migrate_zero_copy_send(void);
  * check, but they are not a capability.
  */
 
+bool migrate_multifd_flush_after_each_section(void);
 bool migrate_postcopy(void);
 bool migrate_tls(void);
 
-- 
2.39.3