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GET /api/patches/2216198/?format=api
{ "id": 2216198, "url": "http://patchwork.ozlabs.org/api/patches/2216198/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260326025825.2427332-1-guoqing.zhang@amd.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/projects/14/?format=api", "name": "QEMU Development", "link_name": "qemu-devel", "list_id": "qemu-devel.nongnu.org", "list_email": "qemu-devel@nongnu.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260326025825.2427332-1-guoqing.zhang@amd.com>", "list_archive_url": null, "date": "2026-03-26T02:58:25", "name": "[v2] migration/rdma: add x-rdma-chunk-size parameter", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "2ce1ff8e827674498d061f471cc4c7cf2c32ad51", "submitter": { "id": 92875, "url": "http://patchwork.ozlabs.org/api/people/92875/?format=api", "name": "Samuel Zhang", "email": "guoqing.zhang@amd.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260326025825.2427332-1-guoqing.zhang@amd.com/mbox/", "series": [ { "id": 497530, "url": "http://patchwork.ozlabs.org/api/series/497530/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=497530", "date": "2026-03-26T02:58:25", "name": "[v2] migration/rdma: add x-rdma-chunk-size parameter", "version": 2, "mbox": "http://patchwork.ozlabs.org/series/497530/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2216198/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2216198/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=amd.com header.i=@amd.com header.a=rsa-sha256\n header.s=selector1 header.b=Nl3ArU10;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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helo=satlexmb07.amd.com; pr=C", "permerror client-ip=40.107.209.21;\n envelope-from=GuoQing.Zhang@amd.com;\n helo=PH8PR06CU001.outbound.protection.outlook.com" ], "From": "Samuel Zhang <guoqing.zhang@amd.com>", "To": "<qemu-devel@nongnu.org>", "CC": "<peterx@redhat.com>, <farosas@suse.de>, <lizhijian@fujitsu.com>,\n <eblake@redhat.com>, <armbru@redhat.com>, <Emily.Deng@amd.com>,\n <Victor.Zhao@amd.com>, <PengJu.Zhou@amd.com>, <Qing.Ma@amd.com>, Samuel Zhang\n <guoqing.zhang@amd.com>", "Subject": "[PATCH v2] migration/rdma: add x-rdma-chunk-size parameter", "Date": "Thu, 26 Mar 2026 10:58:25 +0800", "Message-ID": "<20260326025825.2427332-1-guoqing.zhang@amd.com>", "X-Mailer": "git-send-email 2.43.7", "In-Reply-To": "<20260316062308.1240426-1-guoqing.zhang@amd.com>", "References": "<20260316062308.1240426-1-guoqing.zhang@amd.com>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "Content-Type": "text/plain", "X-Originating-IP": "[10.180.168.240]", "X-ClientProxiedBy": "satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com\n (10.181.42.216)", "X-EOPAttributedMessage": "0", "X-MS-PublicTrafficType": "Email", "X-MS-TrafficTypeDiagnostic": "MN1PEPF0000ECDA:EE_|PH7PR12MB7871:EE_", "X-MS-Office365-Filtering-Correlation-Id": "2ca5fda3-146d-428d-8706-08de8ae3f3a4", "X-MS-Exchange-SenderADCheck": "1", "X-MS-Exchange-AntiSpam-Relay": "0", "X-Microsoft-Antispam": "BCL:0;\n ARA:13230040|82310400026|36860700016|1800799024|376014|22082099003|56012099003|18002099003;", "X-Microsoft-Antispam-Message-Info": "\n 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", "X-Forefront-Antispam-Report": "CIP:165.204.84.17; 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Ip=[165.204.84.17];\n Helo=[satlexmb07.amd.com]", "X-MS-Exchange-CrossTenant-AuthSource": "\n MN1PEPF0000ECDA.namprd02.prod.outlook.com", "X-MS-Exchange-CrossTenant-AuthAs": "Anonymous", "X-MS-Exchange-CrossTenant-FromEntityHeader": "HybridOnPrem", "X-MS-Exchange-Transport-CrossTenantHeadersStamped": "PH7PR12MB7871", "X-Spam_score_int": "-20", "X-Spam_score": "-2.1", "X-Spam_bar": "--", "X-Spam_report": "(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no", "X-Spam_action": "no action", "X-BeenThere": "qemu-devel@nongnu.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "qemu development <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "The default 1MB RDMA chunk size causes slow live migration because\neach chunk triggers a write_flush (ibv_post_send). For 8GB RAM,\n1MB chunk size produce ~15000 flushes vs ~3700 with 1024MB chunk size.\n\nAdd x-rdma-chunk-size parameter to configure the RDMA chunk size for\nfaster migration.\nUsage: `migrate_set_parameter x-rdma-chunk-size 1024M`\n\nPerformance with RDMA live migration of 8GB RAM VM:\n\n| x-rdma-chunk-size (B) | time (s) | throughput (MB/s) |\n|-----------------------|----------|-------------------|\n| 1M (default) | 37.915 | 1,007 |\n| 32M | 17.880 | 2,260 |\n| 1024M | 4.368 | 17,529 |\n\nSigned-off-by: Samuel Zhang <guoqing.zhang@amd.com>\n---\nv2:\n- Renamed x-rdma-chunk-shift to x-rdma-chunk-size (byte count)\n- Added validation in migrate_params_check()\n- Added hmp_migrate_set_parameter() support\n- Added hmp_info_migrate_parameters() support\n- Added migrate_mark_all_params_present()\n- Use qemu_strtosz() for size suffix support\n\n migration/migration-hmp-cmds.c | 17 +++++++++++++++++\n migration/options.c | 32 +++++++++++++++++++++++++++++++-\n migration/options.h | 1 +\n migration/rdma.c | 30 ++++++++++++++++--------------\n qapi/migration.json | 11 +++++++++--\n 5 files changed, 74 insertions(+), 17 deletions(-)", "diff": "diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c\nindex 0a193b8f54..2c005c08a6 100644\n--- a/migration/migration-hmp-cmds.c\n+++ b/migration/migration-hmp-cmds.c\n@@ -451,6 +451,13 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict)\n params->direct_io ? \"on\" : \"off\");\n }\n \n+ if (params->has_x_rdma_chunk_size) {\n+ monitor_printf(mon, \"%s: %\" PRIu64 \" bytes\\n\",\n+ MigrationParameter_str(\n+ MIGRATION_PARAMETER_X_RDMA_CHUNK_SIZE),\n+ params->x_rdma_chunk_size);\n+ }\n+\n assert(params->has_cpr_exec_command);\n monitor_print_cpr_exec_command(mon, params->cpr_exec_command);\n }\n@@ -730,6 +737,16 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict)\n p->has_mode = true;\n visit_type_MigMode(v, param, &p->mode, &err);\n break;\n+ case MIGRATION_PARAMETER_X_RDMA_CHUNK_SIZE:\n+ p->has_x_rdma_chunk_size = true;\n+ ret = qemu_strtosz(valuestr, NULL, &valuebw);\n+ if (ret != 0 || valuebw < (1<<20) || valuebw > (1<<30)\n+ || !is_power_of_2(valuebw)) {\n+ error_setg(&err, \"Invalid size %s\", valuestr);\n+ break;\n+ }\n+ p->x_rdma_chunk_size = valuebw;\n+ break;\n case MIGRATION_PARAMETER_DIRECT_IO:\n p->has_direct_io = true;\n visit_type_bool(v, param, &p->direct_io, &err);\ndiff --git a/migration/options.c b/migration/options.c\nindex f33b297929..91dd874b5e 100644\n--- a/migration/options.c\n+++ b/migration/options.c\n@@ -90,6 +90,7 @@ const PropertyInfo qdev_prop_StrOrNull;\n \n #define DEFAULT_MIGRATE_VCPU_DIRTY_LIMIT_PERIOD 1000 /* milliseconds */\n #define DEFAULT_MIGRATE_VCPU_DIRTY_LIMIT 1 /* MB/s */\n+#define DEFAULT_MIGRATE_X_RDMA_CHUNK_SIZE (1<<20) /* 1MB */\n \n const Property migration_properties[] = {\n DEFINE_PROP_BOOL(\"store-global-state\", MigrationState,\n@@ -183,6 +184,9 @@ const Property migration_properties[] = {\n DEFINE_PROP_ZERO_PAGE_DETECTION(\"zero-page-detection\", MigrationState,\n parameters.zero_page_detection,\n ZERO_PAGE_DETECTION_MULTIFD),\n+ DEFINE_PROP_UINT64(\"x-rdma-chunk-size\", MigrationState,\n+ parameters.x_rdma_chunk_size,\n+ DEFAULT_MIGRATE_X_RDMA_CHUNK_SIZE),\n \n /* Migration capabilities */\n DEFINE_PROP_MIG_CAP(\"x-xbzrle\", MIGRATION_CAPABILITY_XBZRLE),\n@@ -993,6 +997,15 @@ ZeroPageDetection migrate_zero_page_detection(void)\n return s->parameters.zero_page_detection;\n }\n \n+uint64_t migrate_rdma_chunk_size(void)\n+{\n+ MigrationState *s = migrate_get_current();\n+ uint64_t size = s->parameters.x_rdma_chunk_size;\n+\n+ assert((1<<20) <= size && size <= (1<<30) && is_power_of_2(size));\n+ return size;\n+}\n+\n /* parameters helpers */\n \n AnnounceParameters *migrate_announce_params(void)\n@@ -1055,7 +1068,7 @@ static void migrate_mark_all_params_present(MigrationParameters *p)\n &p->has_announce_step, &p->has_block_bitmap_mapping,\n &p->has_x_vcpu_dirty_limit_period, &p->has_vcpu_dirty_limit,\n &p->has_mode, &p->has_zero_page_detection, &p->has_direct_io,\n- &p->has_cpr_exec_command,\n+ &p->has_x_rdma_chunk_size, &p->has_cpr_exec_command,\n };\n \n len = ARRAY_SIZE(has_fields);\n@@ -1227,6 +1240,15 @@ bool migrate_params_check(MigrationParameters *params, Error **errp)\n return false;\n }\n \n+ if (params->has_x_rdma_chunk_size &&\n+ (params->x_rdma_chunk_size < (1<<20) ||\n+ params->x_rdma_chunk_size > (1<<30) ||\n+ !is_power_of_2(params->x_rdma_chunk_size))) {\n+ error_setg(errp, \"Option x_rdma_chunk_size expects \"\n+ \"a power of 2 in the range 1M to 1024M\");\n+ return false;\n+ }\n+\n if (!check_dirty_bitmap_mig_alias_map(params->block_bitmap_mapping, errp)) {\n error_prepend(errp, \"Invalid mapping given for block-bitmap-mapping: \");\n return false;\n@@ -1391,6 +1413,10 @@ static void migrate_params_test_apply(MigrationParameters *params,\n dest->direct_io = params->direct_io;\n }\n \n+ if (params->has_x_rdma_chunk_size) {\n+ dest->x_rdma_chunk_size = params->x_rdma_chunk_size;\n+ }\n+\n if (params->has_cpr_exec_command) {\n dest->cpr_exec_command = params->cpr_exec_command;\n }\n@@ -1517,6 +1543,10 @@ static void migrate_params_apply(MigrationParameters *params)\n s->parameters.direct_io = params->direct_io;\n }\n \n+ if (params->has_x_rdma_chunk_size) {\n+ s->parameters.x_rdma_chunk_size = params->x_rdma_chunk_size;\n+ }\n+\n if (params->has_cpr_exec_command) {\n qapi_free_strList(s->parameters.cpr_exec_command);\n s->parameters.cpr_exec_command =\ndiff --git a/migration/options.h b/migration/options.h\nindex b502871097..b46221998a 100644\n--- a/migration/options.h\n+++ b/migration/options.h\n@@ -87,6 +87,7 @@ const char *migrate_tls_creds(void);\n const char *migrate_tls_hostname(void);\n uint64_t migrate_xbzrle_cache_size(void);\n ZeroPageDetection migrate_zero_page_detection(void);\n+uint64_t migrate_rdma_chunk_size(void);\n \n /* parameters helpers */\n \ndiff --git a/migration/rdma.c b/migration/rdma.c\nindex 55ab85650a..3e37a1d440 100644\n--- a/migration/rdma.c\n+++ b/migration/rdma.c\n@@ -45,10 +45,12 @@\n #define RDMA_RESOLVE_TIMEOUT_MS 10000\n \n /* Do not merge data if larger than this. */\n-#define RDMA_MERGE_MAX (2 * 1024 * 1024)\n-#define RDMA_SIGNALED_SEND_MAX (RDMA_MERGE_MAX / 4096)\n+static inline uint64_t rdma_merge_max(void)\n+{\n+ return migrate_rdma_chunk_size() * 2;\n+}\n \n-#define RDMA_REG_CHUNK_SHIFT 20 /* 1 MB */\n+#define RDMA_SIGNALED_SEND_MAX 512\n \n /*\n * This is only for non-live state being migrated.\n@@ -527,21 +529,21 @@ static int qemu_rdma_exchange_send(RDMAContext *rdma, RDMAControlHeader *head,\n static inline uint64_t ram_chunk_index(const uint8_t *start,\n const uint8_t *host)\n {\n- return ((uintptr_t) host - (uintptr_t) start) >> RDMA_REG_CHUNK_SHIFT;\n+ return ((uintptr_t) host - (uintptr_t) start) / migrate_rdma_chunk_size();\n }\n \n static inline uint8_t *ram_chunk_start(const RDMALocalBlock *rdma_ram_block,\n uint64_t i)\n {\n return (uint8_t *)(uintptr_t)(rdma_ram_block->local_host_addr +\n- (i << RDMA_REG_CHUNK_SHIFT));\n+ (i * migrate_rdma_chunk_size()));\n }\n \n static inline uint8_t *ram_chunk_end(const RDMALocalBlock *rdma_ram_block,\n uint64_t i)\n {\n uint8_t *result = ram_chunk_start(rdma_ram_block, i) +\n- (1UL << RDMA_REG_CHUNK_SHIFT);\n+ migrate_rdma_chunk_size();\n \n if (result > (rdma_ram_block->local_host_addr + rdma_ram_block->length)) {\n result = rdma_ram_block->local_host_addr + rdma_ram_block->length;\n@@ -1841,6 +1843,7 @@ static int qemu_rdma_write_one(RDMAContext *rdma,\n struct ibv_send_wr *bad_wr;\n int reg_result_idx, ret, count = 0;\n uint64_t chunk, chunks;\n+ uint64_t chunk_size = migrate_rdma_chunk_size();\n uint8_t *chunk_start, *chunk_end;\n RDMALocalBlock *block = &(rdma->local_ram_blocks.block[current_index]);\n RDMARegister reg;\n@@ -1861,22 +1864,21 @@ retry:\n chunk_start = ram_chunk_start(block, chunk);\n \n if (block->is_ram_block) {\n- chunks = length / (1UL << RDMA_REG_CHUNK_SHIFT);\n+ chunks = length / chunk_size;\n \n- if (chunks && ((length % (1UL << RDMA_REG_CHUNK_SHIFT)) == 0)) {\n+ if (chunks && ((length % chunk_size) == 0)) {\n chunks--;\n }\n } else {\n- chunks = block->length / (1UL << RDMA_REG_CHUNK_SHIFT);\n+ chunks = block->length / chunk_size;\n \n- if (chunks && ((block->length % (1UL << RDMA_REG_CHUNK_SHIFT)) == 0)) {\n+ if (chunks && ((block->length % chunk_size) == 0)) {\n chunks--;\n }\n }\n \n trace_qemu_rdma_write_one_top(chunks + 1,\n- (chunks + 1) *\n- (1UL << RDMA_REG_CHUNK_SHIFT) / 1024 / 1024);\n+ (chunks + 1) * chunk_size / 1024 / 1024);\n \n chunk_end = ram_chunk_end(block, chunk + chunks);\n \n@@ -2176,7 +2178,7 @@ static int qemu_rdma_write(RDMAContext *rdma,\n rdma->current_length += len;\n \n /* flush it if buffer is too large */\n- if (rdma->current_length >= RDMA_MERGE_MAX) {\n+ if (rdma->current_length >= rdma_merge_max()) {\n return qemu_rdma_write_flush(rdma, errp);\n }\n \n@@ -3522,7 +3524,7 @@ int rdma_registration_handle(QEMUFile *f)\n } else {\n chunk = reg->key.chunk;\n host_addr = block->local_host_addr +\n- (reg->key.chunk * (1UL << RDMA_REG_CHUNK_SHIFT));\n+ (reg->key.chunk * migrate_rdma_chunk_size());\n /* Check for particularly bad chunk value */\n if (host_addr < (void *)block->local_host_addr) {\n error_report(\"rdma: bad chunk for block %s\"\ndiff --git a/qapi/migration.json b/qapi/migration.json\nindex 7134d4ce47..94d2c1c65f 100644\n--- a/qapi/migration.json\n+++ b/qapi/migration.json\n@@ -806,7 +806,7 @@\n #\n # Features:\n #\n-# @unstable: Members @x-checkpoint-delay and\n+# @unstable: Members @x-checkpoint-delay, @x-rdma-chunk-size, and\n # @x-vcpu-dirty-limit-period are experimental.\n #\n # Since: 2.4\n@@ -831,6 +831,7 @@\n 'mode',\n 'zero-page-detection',\n 'direct-io',\n+ { 'name': 'x-rdma-chunk-size', 'features': [ 'unstable' ] },\n 'cpr-exec-command'] }\n \n ##\n@@ -1007,9 +1008,13 @@\n # is @cpr-exec. The first list element is the program's filename,\n # the remainder its arguments. (Since 10.2)\n #\n+# @x-rdma-chunk-size: RDMA memory registration chunk size in bytes.\n+# Default is 1M. Must be a power of 2 in the range [1M, 1024M].\n+# Only takes effect for RDMA migration. (Since 11.1)\n+#\n # Features:\n #\n-# @unstable: Members @x-checkpoint-delay and\n+# @unstable: Members @x-checkpoint-delay, @x-rdma-chunk-size, and\n # @x-vcpu-dirty-limit-period are experimental.\n #\n # Since: 2.4\n@@ -1046,6 +1051,8 @@\n '*mode': 'MigMode',\n '*zero-page-detection': 'ZeroPageDetection',\n '*direct-io': 'bool',\n+ '*x-rdma-chunk-size': { 'type': 'uint64',\n+ 'features': [ 'unstable' ] },\n '*cpr-exec-command': [ 'str' ]} }\n \n ##\n", "prefixes": [ "v2" ] }