Like in the normal ram_load() path, put the received pages into the colo cache and mark the pages in the bitmap so that they will be flushed to the guest later.
Multifd with COLO is useful to reduce the VM pause time during checkpointing for latency sensitive workloads. In such workloads the worst-case latency is especially important. Also, this is already worth it for the precopy phase as it helps with converging. Moreover, multifd migration is the preferred way to do migration nowadays and this allows to use multifd compression with COLO. Benchmark: Cluster nodes - Intel Xenon E5-2630 v3 - 48Gb RAM - 10G Ethernet Guest - Windows Server 2016 - 6Gb RAM - 4 cores Workload - Upload a file to the guest with SMB to simulate moderate memory dirtying - Measure the memory transfer time portion of each checkpoint - 600ms COLO checkpoint interval Results Plain idle mean: 4.50ms 99per: 10.33ms load mean: 24.30ms 99per: 78.05ms Multifd-4 idle mean: 6.48ms 99per: 10.41ms load mean: 14.12ms 99per: 31.27ms Evaluation While multifd has slightly higher latency when the guest idles, it is 10ms faster under load and more importantly it's worst case latency is less than 1/2 of plain under load as can be seen in the 99. Percentile. Signed-off-by: Juan Quintela <[email protected]> Signed-off-by: Lukas Straub <[email protected]> --- MAINTAINERS | 1 + migration/meson.build | 2 +- migration/multifd-colo.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++ migration/multifd-colo.h | 26 ++++++++++++++++++++++++ migration/multifd-nocomp.c | 10 +++++++++- migration/multifd.c | 8 ++++++++ migration/multifd.h | 5 ++++- 7 files changed, 99 insertions(+), 3 deletions(-) diff --git a/MAINTAINERS b/MAINTAINERS index 1e9bdd87c3a2f84f3abfc56986cd793976810fdd..883f0a8f4eb92d0bf0f89fcab4674ccc4aed1cc1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3853,6 +3853,7 @@ COLO Framework M: Lukas Straub <[email protected]> S: Maintained F: migration/colo* +F: migration/multifd-colo.* F: include/migration/colo.h F: include/migration/failover.h F: docs/COLO-FT.txt diff --git a/migration/meson.build b/migration/meson.build index c7f39bdb55239ecb0e775c77b90a1aa9e6a4a9ce..c9f0f5f9f2137536497e53e960ce70654ad1b394 100644 --- a/migration/meson.build +++ b/migration/meson.build @@ -39,7 +39,7 @@ system_ss.add(files( ), gnutls, zlib) if get_option('replication').allowed() - system_ss.add(files('colo-failover.c', 'colo.c')) + system_ss.add(files('colo-failover.c', 'colo.c', 'multifd-colo.c')) else system_ss.add(files('colo-stubs.c')) endif diff --git a/migration/multifd-colo.c b/migration/multifd-colo.c new file mode 100644 index 0000000000000000000000000000000000000000..c47f5044663969e0c9af56da5ec34902d635810a --- /dev/null +++ b/migration/multifd-colo.c @@ -0,0 +1,50 @@ +/* + * SPDX-License-Identifier: GPL-2.0-or-later + * + * multifd colo implementation + * + * Copyright (c) Lukas Straub <[email protected]> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "exec/target_page.h" +#include "qemu/error-report.h" +#include "qapi/error.h" +#include "ram.h" +#include "multifd.h" +#include "options.h" +#include "io/channel-socket.h" +#include "migration/colo.h" +#include "multifd-colo.h" +#include "system/ramblock.h" + +void multifd_colo_prepare_recv(MultiFDRecvParams *p) +{ + /* + * While we're still in precopy state (not yet in colo state), we copy + * received pages to both guest and cache. No need to set dirty bits, + * since guest and cache memory are in sync. + */ + if (migration_incoming_in_colo_state()) { + colo_record_bitmap(p->block, p->normal, p->normal_num); + colo_record_bitmap(p->block, p->zero, p->zero_num); + } +} + +void multifd_colo_process_recv(MultiFDRecvParams *p) +{ + if (!migration_incoming_in_colo_state()) { + for (int i = 0; i < p->normal_num; i++) { + void *guest = p->block->host + p->normal[i]; + void *cache = p->host + p->normal[i]; + memcpy(guest, cache, multifd_ram_page_size()); + } + for (int i = 0; i < p->zero_num; i++) { + void *guest = p->block->host + p->zero[i]; + memset(guest, 0, multifd_ram_page_size()); + } + } +} diff --git a/migration/multifd-colo.h b/migration/multifd-colo.h new file mode 100644 index 0000000000000000000000000000000000000000..82eaf3f48c47de2f090f9de52f9d57a337d4754a --- /dev/null +++ b/migration/multifd-colo.h @@ -0,0 +1,26 @@ +/* + * SPDX-License-Identifier: GPL-2.0-or-later + * + * multifd colo header + * + * Copyright (c) Lukas Straub <[email protected]> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#ifndef QEMU_MIGRATION_MULTIFD_COLO_H +#define QEMU_MIGRATION_MULTIFD_COLO_H + +#ifdef CONFIG_REPLICATION + +void multifd_colo_prepare_recv(MultiFDRecvParams *p); +void multifd_colo_process_recv(MultiFDRecvParams *p); + +#else + +static inline void multifd_colo_prepare_recv(MultiFDRecvParams *p) {} +static inline void multifd_colo_process_recv(MultiFDRecvParams *p) {} + +#endif +#endif diff --git a/migration/multifd-nocomp.c b/migration/multifd-nocomp.c index 9be79b3b8e00371ebff9e112766c225bec260bf7..9f7a792fa761b3bc30b971b35f464103a61787f0 100644 --- a/migration/multifd-nocomp.c +++ b/migration/multifd-nocomp.c @@ -16,6 +16,7 @@ #include "file.h" #include "migration-stats.h" #include "multifd.h" +#include "multifd-colo.h" #include "options.h" #include "migration.h" #include "qapi/error.h" @@ -269,7 +270,6 @@ int multifd_ram_unfill_packet(MultiFDRecvParams *p, Error **errp) return -1; } - p->host = p->block->host; for (i = 0; i < p->normal_num; i++) { uint64_t offset = be64_to_cpu(packet->offset[i]); @@ -294,6 +294,14 @@ int multifd_ram_unfill_packet(MultiFDRecvParams *p, Error **errp) p->zero[i] = offset; } + if (migrate_colo()) { + multifd_colo_prepare_recv(p); + assert(p->block->colo_cache); + p->host = p->block->colo_cache; + } else { + p->host = p->block->host; + } + return 0; } diff --git a/migration/multifd.c b/migration/multifd.c index 332e6fc58053462419f3171f6c320ac37648ef7b..220ed8564960fdabc58e4baa069dd252c8ad293c 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -29,6 +29,7 @@ #include "qemu-file.h" #include "trace.h" #include "multifd.h" +#include "multifd-colo.h" #include "options.h" #include "qemu/yank.h" #include "io/channel-file.h" @@ -1258,6 +1259,13 @@ static int multifd_ram_state_recv(MultiFDRecvParams *p, Error **errp) int ret; ret = multifd_recv_state->ops->recv(p, errp); + if (ret != 0) { + return ret; + } + + if (migrate_colo()) { + multifd_colo_process_recv(p); + } return ret; } diff --git a/migration/multifd.h b/migration/multifd.h index 89a395aef2b09a6762c45b5361e0ab63256feff6..fbc35702b062fdc3213ce92baed35994f5967c2b 100644 --- a/migration/multifd.h +++ b/migration/multifd.h @@ -279,7 +279,10 @@ typedef struct { uint64_t packets_recved; /* ramblock */ RAMBlock *block; - /* ramblock host address */ + /* + * Normally, it points to ramblock's host address. When COLO + * is enabled, it points to the mirror cache for the ramblock. + */ uint8_t *host; /* buffers to recv */ struct iovec *iov; -- 2.39.5
