This implements the zero page dection and handling. Signed-off-by: Juan Quintela <quint...@redhat.com>
--- Add comment for offset (dave) Use local variables for offset/block to have shorter lines --- migration/multifd.h | 5 +++++ migration/multifd.c | 41 +++++++++++++++++++++++++++++++++++++++-- 2 files changed, 44 insertions(+), 2 deletions(-) diff --git a/migration/multifd.h b/migration/multifd.h index c36d7ff876..209e3a9756 100644 --- a/migration/multifd.h +++ b/migration/multifd.h @@ -52,6 +52,11 @@ typedef struct { uint32_t unused32[1]; /* Reserved for future use */ uint64_t unused64[3]; /* Reserved for future use */ char ramblock[256]; + /* + * This array contains the pointers to: + * - normal pages (initial normal_pages entries) + * - zero pages (following zero_pages entries) + */ uint64_t offset[]; } __attribute__((packed)) MultiFDPacket_t; diff --git a/migration/multifd.c b/migration/multifd.c index 0f7c27c08e..fcdd241c5c 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -11,6 +11,7 @@ */ #include "qemu/osdep.h" +#include "qemu/cutils.h" #include "qemu/rcu.h" #include "exec/target_page.h" #include "sysemu/sysemu.h" @@ -275,6 +276,12 @@ static void multifd_send_fill_packet(MultiFDSendParams *p) packet->offset[i] = cpu_to_be64(temp); } + for (i = 0; i < p->zero_num; i++) { + /* there are architectures where ram_addr_t is 32 bit */ + uint64_t temp = p->zero[i]; + + packet->offset[p->normal_num + i] = cpu_to_be64(temp); + } } static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp) @@ -358,6 +365,18 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp) p->normal[i] = offset; } + for (i = 0; i < p->zero_num; i++) { + uint64_t offset = be64_to_cpu(packet->offset[p->normal_num + i]); + + if (offset > (block->used_length - p->page_size)) { + error_setg(errp, "multifd: offset too long %" PRIu64 + " (max " RAM_ADDR_FMT ")", + offset, block->used_length); + return -1; + } + p->zero[i] = offset; + } + return 0; } @@ -646,6 +665,8 @@ static void *multifd_send_thread(void *opaque) { MultiFDSendParams *p = opaque; Error *local_err = NULL; + /* qemu older than 7.0 don't understand zero page on multifd channel */ + bool use_zero_page = migrate_use_multifd_zero_page(); int ret = 0; bool use_zero_copy_send = migrate_use_zero_copy_send(); @@ -668,6 +689,7 @@ static void *multifd_send_thread(void *opaque) qemu_mutex_lock(&p->mutex); if (p->pending_job) { + RAMBlock *rb = p->pages->block; uint64_t packet_num = p->packet_num; p->flags = 0; if (p->sync_needed) { @@ -686,8 +708,16 @@ static void *multifd_send_thread(void *opaque) } for (int i = 0; i < p->pages->num; i++) { - p->normal[p->normal_num] = p->pages->offset[i]; - p->normal_num++; + uint64_t offset = p->pages->offset[i]; + if (use_zero_page && + buffer_is_zero(rb->host + offset, p->page_size)) { + p->zero[p->zero_num] = offset; + p->zero_num++; + ram_release_page(rb->idstr, offset); + } else { + p->normal[p->normal_num] = offset; + p->normal_num++; + } } if (p->normal_num) { @@ -1152,6 +1182,13 @@ static void *multifd_recv_thread(void *opaque) } } + for (int i = 0; i < p->zero_num; i++) { + void *page = p->host + p->zero[i]; + if (!buffer_is_zero(page, p->page_size)) { + memset(page, 0, p->page_size); + } + } + if (sync_needed) { qemu_sem_post(&multifd_recv_state->sem_sync); qemu_sem_wait(&p->sem_sync); -- 2.35.3