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Re: [RFC 6/6] migration: Deprecated old compression method

From: Thomas Huth
Subject: Re: [RFC 6/6] migration: Deprecated old compression method
Date: Wed, 21 Jun 2023 09:14:27 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 
On 12/06/2023 21.33, Juan Quintela wrote:

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
  docs/about/deprecated.rst |  8 ++++
  qapi/migration.json       | 92 ++++++++++++++++++++++++---------------
  migration/options.c       | 13 ++++++
  3 files changed, 79 insertions(+), 34 deletions(-)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 173c5ba5cb..fe7f2bbde8 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -460,3 +460,11 @@ block migration (since 8.1)
  Block migration is too inflexible.  It needs to migrate all block
  devices or none.  Use driver_mirror+NBD instead.
+old compression method (since 8.1) 
+''''''''''''''''''''''''''''''''''
+
+Compression method fails too much.  Too many races.  We are going to
+remove it if nobody fixes it.  For starters, migration-test
+compression tests are disabled becase they hand randomly.  If you need


"because they fail randomly" ?


+compression, use multifd compression methods.
+
diff --git a/qapi/migration.json b/qapi/migration.json
index a8497de48d..40a8b5d124 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -244,6 +244,7 @@
  #
  # @compression: migration compression statistics, only returned if
  #     compression feature is on and status is 'active' or 'completed'
+#     It is obsolete and deprecated.  Use multifd compression methods.
  #     (Since 3.1)
  #
  # @socket-address: Only used for tcp, to know what the real port is
@@ -261,7 +262,8 @@
  # Features:
  #
  # @deprecated: @disk migration is deprecated.  Use driver_mirror+NBD
-#     instead.
+#     instead. @compression is obsolete use multifd compression


Use a dot or comma after "obsolete".


+#     methods instead.
  #
  # Since: 0.14
  ##
@@ -279,7 +281,7 @@
             '*blocked-reasons': ['str'],
             '*postcopy-blocktime': 'uint32',
             '*postcopy-vcpu-blocktime': ['uint32'],
-           '*compression': 'CompressionStats',
+           '*compression': { 'type': 'CompressionStats', 'features': 
['deprecated'] },
             '*socket-address': ['SocketAddress'] } }
## 
@@ -432,7 +434,8 @@
  #     compress and xbzrle are both on, compress only takes effect in
  #     the ram bulk stage, after that, it will be disabled and only
  #     xbzrle takes effect, this can help to minimize migration
-#     traffic.  The feature is disabled by default.  (since 2.4 )
+#     traffic.  The feature is disabled by default.  Obsolete.  Use
+#     multifd compression methods if needed. (since 2.4 )
  #
  # @events: generate events for each migration state change (since 2.4
  #     )
@@ -503,6 +506,7 @@
  # Features:
  #
  # @deprecated: @block migration is deprecated.  Use driver_mirror+NBD
+#     instead. @compress is obsolete use multifd compression methods


dito


  #     instead.
  #
  # @unstable: Members @x-colo and @x-ignore-shared are experimental.
@@ -511,7 +515,8 @@
  ##
  { 'enum': 'MigrationCapability',
    'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
-           'compress', 'events', 'postcopy-ram',
+           { 'name': 'compress', 'features': [ 'deprecated' ] },
+           'events', 'postcopy-ram',
             { 'name': 'x-colo', 'features': [ 'unstable' ] },
             'release-ram',
             { 'name': 'block', 'features': [ 'deprecated' ] },
@@ -671,22 +676,24 @@
  #     migration, the compression level is an integer between 0 and 9,
  #     where 0 means no compression, 1 means the best compression
  #     speed, and 9 means best compression ratio which will consume
-#     more CPU.
+#     more CPU. Obsolete, see multifd compression if needed.
  #
  # @compress-threads: Set compression thread count to be used in live
  #     migration, the compression thread count is an integer between 1
-#     and 255.
+#     and 255. Obsolete, see multifd compression if needed.
  #
  # @compress-wait-thread: Controls behavior when all compression
  #     threads are currently busy.  If true (default), wait for a free
  #     compression thread to become available; otherwise, send the page
-#     uncompressed.  (Since 3.1)
+#     uncompressed. Obsolete, see multifd compression if
+#     needed. (Since 3.1)
  #
  # @decompress-threads: Set decompression thread count to be used in
  #     live migration, the decompression thread count is an integer
  #     between 1 and 255. Usually, decompression is at least 4 times as
  #     fast as compression, so set the decompress-threads to the number
-#     about 1/4 of compress-threads is adequate.
+#     about 1/4 of compress-threads is adequate. Obsolete, see multifd
+#     compression if needed.
  #
  # @throttle-trigger-threshold: The ratio of bytes_dirty_period and
  #     bytes_xfer_period to trigger throttling.  It is expressed as
@@ -799,7 +806,9 @@
  # Features:
  #
  # @deprecated: Member @block-incremental is obsolete. Use
-#     driver_mirror+NBD instead.
+#     driver_mirror+NBD instead. Compression is obsolete, so members
+#     @compress-level, @compress-threads, @decompress-threads and
+#     @compress-wait-thread should not be used.
  #
  # @unstable: Member @x-checkpoint-delay is experimental.
  #
@@ -808,8 +817,11 @@
  { 'enum': 'MigrationParameter',
    'data': ['announce-initial', 'announce-max',
             'announce-rounds', 'announce-step',
-           'compress-level', 'compress-threads', 'decompress-threads',
-           'compress-wait-thread', 'throttle-trigger-threshold',
+           { 'name': 'compress-level', 'features': [ 'deprecated' ] },
+           { 'name': 'compress-threads', 'features': [ 'deprecated' ] },
+           { 'name': 'decompress-threads', 'features': [ 'deprecated' ] },
+           { 'name': 'compress-wait-thread', 'features': [ 'deprecated' ] },
+           'throttle-trigger-threshold',
             'cpu-throttle-initial', 'cpu-throttle-increment',
             'cpu-throttle-tailslow',
             'tls-creds', 'tls-hostname', 'tls-authz', 'max-bandwidth',
@@ -837,16 +849,17 @@
  # @announce-step: Increase in delay (in milliseconds) between
  #     subsequent packets in the announcement (Since 4.0)
  #
-# @compress-level: compression level
+# @compress-level: compression level. Obsolete and deprecated.
  #
-# @compress-threads: compression thread count
+# @compress-threads: compression thread count. Obsolete and deprecated.
  #
  # @compress-wait-thread: Controls behavior when all compression
  #     threads are currently busy.  If true (default), wait for a free
  #     compression thread to become available; otherwise, send the page
-#     uncompressed.  (Since 3.1)
+#     uncompressed.  Obsolete and deprecated. (Since 3.1)
  #
-# @decompress-threads: decompression thread count
+# @decompress-threads: decompression thread count. Obsolete and
+#     deprecated.
  #
  # @throttle-trigger-threshold: The ratio of bytes_dirty_period and
  #     bytes_xfer_period to trigger throttling.  It is expressed as
@@ -958,7 +971,9 @@
  # Features:
  #
  # @deprecated: Member @block-incremental is obsolete. Use
-#     driver_mirror+NBD instead.
+#     driver_mirror+NBD instead. Compression is obsolete, so members
+#     @compress-level, @compress-threads, @decompress-threads and
+#     @compress-wait-thread should not be used.
  #
  # @unstable: Member @x-checkpoint-delay is experimental.
  #
@@ -972,10 +987,14 @@
              '*announce-max': 'size',
              '*announce-rounds': 'size',
              '*announce-step': 'size',
-            '*compress-level': 'uint8',
-            '*compress-threads': 'uint8',
-            '*compress-wait-thread': 'bool',
-            '*decompress-threads': 'uint8',
+            '*compress-level': { 'type': 'uint8',
+                                 'features': [ 'deprecated' ] },
+            '*compress-threads':  { 'type': 'uint8',
+                                    'features': [ 'deprecated' ] },
+            '*compress-wait-thread':  { 'type': 'bool',
+                                        'features': [ 'deprecated' ] },
+            '*decompress-threads':  { 'type': 'uint8',
+                                      'features': [ 'deprecated' ] },
              '*throttle-trigger-threshold': 'uint8',
              '*cpu-throttle-initial': 'uint8',
              '*cpu-throttle-increment': 'uint8',
@@ -1008,7 +1027,7 @@
  # Example:
  #
  # -> { "execute": "migrate-set-parameters" ,
-#      "arguments": { "compress-level": 1 } }
+#      "arguments": { "multifd-channels": 5 } }
  # <- { "return": {} }
  ##
  { 'command': 'migrate-set-parameters', 'boxed': true,
@@ -1031,16 +1050,18 @@
  # @announce-step: Increase in delay (in milliseconds) between
  #     subsequent packets in the announcement (Since 4.0)
  #
-# @compress-level: compression level
+# @compress-level: compression level. Obsolete and deprecated.
  #
-# @compress-threads: compression thread count
+# @compress-threads: compression thread count. Obsolote and


Obsolete


+#     deprecated.
  #
  # @compress-wait-thread: Controls behavior when all compression
  #     threads are currently busy.  If true (default), wait for a free
  #     compression thread to become available; otherwise, send the page
-#     uncompressed.  (Since 3.1)
+#     uncompressed. Obsolete and deprecated. (Since 3.1)
  #
-# @decompress-threads: decompression thread count
+# @decompress-threads: decompression thread count. Obsolete and
+#     deprecated.
  #
  # @throttle-trigger-threshold: The ratio of bytes_dirty_period and
  #     bytes_xfer_period to trigger throttling.  It is expressed as
@@ -1154,7 +1175,9 @@
  # Features:
  #
  # @deprecated: Member @block-incremental is obsolete. Use
-#     driver_mirror+NBD instead.
+#     driver_mirror+NBD instead. Compression is obsolete, so members
+#     @compress-level, @compress-threads, @decompress-threads and
+#     @compress-wait-thread should not be used.
  #
  # @unstable: Member @x-checkpoint-delay is experimental.
  #
@@ -1165,10 +1188,14 @@
              '*announce-max': 'size',
              '*announce-rounds': 'size',
              '*announce-step': 'size',
-            '*compress-level': 'uint8',
-            '*compress-threads': 'uint8',
-            '*compress-wait-thread': 'bool',
-            '*decompress-threads': 'uint8',
+            '*compress-level': { 'type': 'uint8',
+                                 'features': [ 'deprecated' ] },
+            '*compress-threads': { 'type': 'uint8',
+                                   'features': [ 'deprecated' ] },
+            '*compress-wait-thread': { 'type': 'bool',
+                                       'features': [ 'deprecated' ] },
+            '*decompress-threads': { 'type': 'uint8',
+                                     'features': [ 'deprecated' ] },
              '*throttle-trigger-threshold': 'uint8',
              '*cpu-throttle-initial': 'uint8',
              '*cpu-throttle-increment': 'uint8',
@@ -1182,7 +1209,6 @@
                                       'features': [ 'unstable' ] },
              '*block-incremental': { 'type': 'bool',
                                      'features': [ 'deprecated' ] },
-            '*block-incremental': 'bool',


That hunk should go into a previous patch, I think.


              '*multifd-channels': 'uint8',
              '*xbzrle-cache-size': 'size',
              '*max-postcopy-bandwidth': 'size',
@@ -1205,10 +1231,8 @@
  #
  # -> { "execute": "query-migrate-parameters" }
  # <- { "return": {
-#          "decompress-threads": 2,
+#          "multifd-channels": 2,
  #          "cpu-throttle-increment": 10,
-#          "compress-threads": 8,
-#          "compress-level": 1,
  #          "cpu-throttle-initial": 20,
  #          "max-bandwidth": 33554432,
  #          "downtime-limit": 300


 Thomas
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