Patchwork [v6,09/11] rdma: introduce capability x-rdma-pin-all

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Submitter mrhines@linux.vnet.ibm.com
Date April 24, 2013, 7 p.m.
Message ID <1366830057-16964-10-git-send-email-mrhines@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/239308/
State New
Headers show

Comments

mrhines@linux.vnet.ibm.com - April 24, 2013, 7 p.m.
From: "Michael R. Hines" <mrhines@us.ibm.com>

This capability allows you to disable dynamic chunk registration
for better throughput on high-performance links.

For example, using an 8GB RAM virtual machine with all 8GB of memory in
active use and the VM itself is completely idle using a 40 gbps infiniband link:

1. x-rdma-pin-all disabled total time: approximately 7.5 seconds @ 9.5 Gbps
2. x-rdma-pin-all enabled total time: approximately 4 seconds @ 26 Gbps

These numbers would of course scale up to whatever size virtual machine
you have to migrate using RDMA.

Enabling this feature does *not* have any measurable affect on
migration *downtime*. This is because, without this feature, all of the
memory will have already been registered already in advance during
the bulk round and does not need to be re-registered during the successive
iteration rounds.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
---
 include/migration/migration.h |    2 ++
 migration.c                   |    9 +++++++++
 qapi-schema.json              |    7 ++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

Patch

diff --git a/include/migration/migration.h b/include/migration/migration.h
index dd86b1c..b9b6c36 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -123,6 +123,8 @@  void migrate_add_blocker(Error *reason);
  */
 void migrate_del_blocker(Error *reason);
 
+bool migrate_rdma_pin_all(void);
+
 int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
                          uint8_t *dst, int dlen);
 int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen);
diff --git a/migration.c b/migration.c
index 4614c95..97ce6d8 100644
--- a/migration.c
+++ b/migration.c
@@ -477,6 +477,15 @@  void qmp_migrate_set_downtime(double value, Error **errp)
     max_downtime = (uint64_t)value;
 }
 
+bool migrate_rdma_pin_all(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_X_RDMA_PIN_ALL];
+}
+
 int migrate_use_xbzrle(void)
 {
     MigrationState *s;
diff --git a/qapi-schema.json b/qapi-schema.json
index cc846c3..d5b8e20 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -602,10 +602,15 @@ 
 #          This feature allows us to minimize migration traffic for certain work
 #          loads, by sending compressed difference of the pages
 #
+# @x-rdma-pin-all: Controls whether or not the entire VM memory footprint is
+#          mlock()'d on demand or all at once. Refer to docs/rdma.txt for usage.
+#          Disabled by default. Experimental: may (or may not) be renamed after
+#          further testing is complete. (since 1.5)
+#
 # Since: 1.2
 ##
 { 'enum': 'MigrationCapability',
-  'data': ['xbzrle'] }
+  'data': ['xbzrle', 'x-rdma-pin-all'] }
 
 ##
 # @MigrationCapabilityStatus