Re: [Qemu-devel] [PATCH v12 10/21] migration: Create multipage support

[Dr. David Alan Gilbert]

* Juan Quintela (address@hidden) wrote:
> We only create/destry the page list here.  We will use it later.
> 
> Signed-off-by: Juan Quintela <address@hidden>
> ---
>  migration/ram.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 56 insertions(+)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index ffefa73099..b19300992e 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -412,6 +412,20 @@ typedef struct {
>      uint8_t id;
>  } __attribute__((packed)) MultiFDInit_t;
>  
> +typedef struct {
> +    /* number of used pages */
> +    uint32_t used;
> +    /* number of allocated pages */
> +    uint32_t allocated;
> +    /* global number of generated multifd packets */
> +    uint32_t seq;

Is that sufficiently large?
Consider a 40Gbps link; that's ~4GByte/second,
so if each packet is a 4K page, that's just over one hour at
that link speed;  that's a long migration on a fast link, but
it's not impossible is it - and what happens when it wraps?

> +    /* offset of each page */
> +    ram_addr_t *offset;
> +    /* pointer to each page */
> +    struct iovec *iov;
> +    RAMBlock *block;
> +} MultiFDPages_t;
> +
>  typedef struct {
>      /* this fields are not changed once the thread is created */
>      /* channel number */
> @@ -430,6 +444,8 @@ typedef struct {
>      bool running;
>      /* should this thread finish */
>      bool quit;
> +    /* array of pages to sent */

s/sent/send/

Dave

> +    MultiFDPages_t *pages;
>  }  MultiFDSendParams;
>  
>  typedef struct {
> @@ -450,6 +466,8 @@ typedef struct {
>      bool running;
>      /* should this thread finish */
>      bool quit;
> +    /* array of pages to receive */
> +    MultiFDPages_t *pages;
>  } MultiFDRecvParams;
>  
>  static int multifd_send_initial_packet(MultiFDSendParams *p, Error **errp)
> @@ -511,10 +529,35 @@ static int multifd_recv_initial_packet(QIOChannel *c, 
> Error **errp)
>      return msg.id;
>  }
>  
> +static void multifd_pages_init(MultiFDPages_t **ppages, size_t size)
> +{
> +    MultiFDPages_t *pages = g_new0(MultiFDPages_t, 1);
> +
> +    pages->allocated = size;
> +    pages->iov = g_new0(struct iovec, size);
> +    pages->offset = g_new0(ram_addr_t, size);
> +    *ppages = pages;
> +}
> +
> +static void multifd_pages_clear(MultiFDPages_t *pages)
> +{
> +    pages->used = 0;
> +    pages->allocated = 0;
> +    pages->seq = 0;
> +    pages->block = NULL;
> +    g_free(pages->iov);
> +    pages->iov = NULL;
> +    g_free(pages->offset);
> +    pages->offset = NULL;
> +    g_free(pages);
> +}
> +
>  struct {
>      MultiFDSendParams *params;
>      /* number of created threads */
>      int count;
> +    /* array of pages to sent */
> +    MultiFDPages_t *pages;
>  } *multifd_send_state;
>  
>  static void multifd_send_terminate_threads(Error *err)
> @@ -562,9 +605,13 @@ int multifd_save_cleanup(Error **errp)
>          qemu_sem_destroy(&p->sem);
>          g_free(p->name);
>          p->name = NULL;
> +        multifd_pages_clear(p->pages);
> +        p->pages = NULL;
>      }
>      g_free(multifd_send_state->params);
>      multifd_send_state->params = NULL;
> +    multifd_pages_clear(multifd_send_state->pages);
> +    multifd_send_state->pages = NULL;
>      g_free(multifd_send_state);
>      multifd_send_state = NULL;
>      return ret;
> @@ -625,6 +672,7 @@ static void multifd_new_send_channel_async(QIOTask *task, 
> gpointer opaque)
>  int multifd_save_setup(void)
>  {
>      int thread_count;
> +    uint32_t page_count = migrate_multifd_page_count();
>      uint8_t i;
>  
>      if (!migrate_use_multifd()) {
> @@ -634,6 +682,8 @@ int multifd_save_setup(void)
>      multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
>      multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
>      atomic_set(&multifd_send_state->count, 0);
> +    multifd_pages_init(&multifd_send_state->pages, page_count);
> +
>      for (i = 0; i < thread_count; i++) {
>          MultiFDSendParams *p = &multifd_send_state->params[i];
>  
> @@ -641,6 +691,7 @@ int multifd_save_setup(void)
>          qemu_sem_init(&p->sem, 0);
>          p->quit = false;
>          p->id = i;
> +        multifd_pages_init(&p->pages, page_count);
>          p->name = g_strdup_printf("multifdsend_%d", i);
>          socket_send_channel_create(multifd_new_send_channel_async, p);
>      }
> @@ -698,6 +749,8 @@ int multifd_load_cleanup(Error **errp)
>          qemu_sem_destroy(&p->sem);
>          g_free(p->name);
>          p->name = NULL;
> +        multifd_pages_clear(p->pages);
> +        p->pages = NULL;
>      }
>      g_free(multifd_recv_state->params);
>      multifd_recv_state->params = NULL;
> @@ -731,6 +784,7 @@ static void *multifd_recv_thread(void *opaque)
>  int multifd_load_setup(void)
>  {
>      int thread_count;
> +    uint32_t page_count = migrate_multifd_page_count();
>      uint8_t i;
>  
>      if (!migrate_use_multifd()) {
> @@ -740,6 +794,7 @@ int multifd_load_setup(void)
>      multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
>      multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
>      atomic_set(&multifd_recv_state->count, 0);
> +
>      for (i = 0; i < thread_count; i++) {
>          MultiFDRecvParams *p = &multifd_recv_state->params[i];
>  
> @@ -747,6 +802,7 @@ int multifd_load_setup(void)
>          qemu_sem_init(&p->sem, 0);
>          p->quit = false;
>          p->id = i;
> +        multifd_pages_init(&p->pages, page_count);
>          p->name = g_strdup_printf("multifdrecv_%d", i);
>      }
>      return 0;
> -- 
> 2.17.0
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK