Re: [Qemu-devel] [RFC PATCH RDMA support v1: 5/5] send memory over RDMA as blocks are iterated

[Orit Wasserman]

Hi Michael,
I maybe missing something here but why do you need a RAM_SAVE_FLAG_RDMA flag?
You don't do any decoding in the destination.

I would suggest creating a QEMUFileRDMA and moving the write/read code
You can either add a new rdma_buffer QEMUFileOps or add the address to 
put_buffer.

you also have some white space damage in the beginning of savevm.c.

Regards,
Orit

On 01/29/2013 12:01 AM, address@hidden wrote
> From: "Michael R. Hines" <address@hidden>
> 
> 
> Signed-off-by: Michael R. Hines <address@hidden>
> ---
>  arch_init.c                   |  116 
> +++++++++++++++++++++++++++++++++++++++--
>  include/migration/qemu-file.h |    1 +
>  savevm.c                      |   90 +++++++++++++++++++++++++++-----
>  3 files changed, 189 insertions(+), 18 deletions(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index dada6de..7633fa6 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -42,6 +42,7 @@
>  #include "migration/migration.h"
>  #include "exec/gdbstub.h"
>  #include "hw/smbios.h"
> +#include "qemu/rdma.h"
>  #include "exec/address-spaces.h"
>  #include "hw/pcspk.h"
>  #include "migration/page_cache.h"
> @@ -113,6 +114,7 @@ const uint32_t arch_type = QEMU_ARCH;
>  #define RAM_SAVE_FLAG_EOS      0x10
>  #define RAM_SAVE_FLAG_CONTINUE 0x20
>  #define RAM_SAVE_FLAG_XBZRLE   0x40
> +#define RAM_SAVE_FLAG_RDMA     0x80
>  
>  #ifdef __ALTIVEC__
>  #include <altivec.h>
> @@ -434,6 +436,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
>      int bytes_sent = 0;
>      MemoryRegion *mr;
>      ram_addr_t current_addr;
> +    static int not_sent = 1;
>  
>      if (!block)
>          block = QTAILQ_FIRST(&ram_list.blocks);
> @@ -457,23 +460,75 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
>              int cont = (block == last_sent_block) ?
>                  RAM_SAVE_FLAG_CONTINUE : 0;
>  
> +            current_addr = block->offset + offset;
>              p = memory_region_get_ram_ptr(mr) + offset;
>  
>              /* In doubt sent page as normal */
>              bytes_sent = -1;
> -            if (is_dup_page(p)) {
> +
> +            /*
> +             * RFC RDMA: The empirical cost of searching for zero pages here
> +             *           plus the cost of communicating with the other side
> +             *           seems to take significantly more time than simply
> +             *           dumping the page into remote memory.
> +             */
> +            if (!qemu_rdma_migration_enabled() && is_dup_page(p)) {
>                  acct_info.dup_pages++;
>                  bytes_sent = save_block_hdr(f, block, offset, cont,
>                                              RAM_SAVE_FLAG_COMPRESS);
>                  qemu_put_byte(f, *p);
>                  bytes_sent += 1;
> +            /*
> +             * RFC RDMA: Same comment as above. time(run-length encoding)
> +             *           + time(communication) is too big. RDMA throughput 
> tanks
> +             *           when this feature is enabled. But there's no need
> +             *           to change the code since the feature is optional.
> +             */
>              } else if (migrate_use_xbzrle()) {
> -                current_addr = block->offset + offset;
>                  bytes_sent = save_xbzrle_page(f, p, current_addr, block,
>                                                offset, cont, last_stage);
>                  if (!last_stage) {
>                      p = get_cached_data(XBZRLE.cache, current_addr);
>                  }
> +            } else if (qemu_rdma_migration_enabled()) {
> +                int ret;
> +
> +                /*
> +                 * RFC RDMA: This bad hack was to cause the loop on the
> +                 *           receiving side to break. Comments are welcome
> +                 *           on how to get rid of it.
> +                 */
> +                if (not_sent == 1) {
> +                        not_sent = 0;
> +                        bytes_sent = save_block_hdr(f, block, offset,
> +                                                cont, RAM_SAVE_FLAG_RDMA);
> +                }
> +                acct_info.norm_pages++;
> +                /*
> +                 * use RDMA to send page
> +                 */
> +                if (qemu_rdma_migration_write(&rdma_mdata, current_addr,
> +                        TARGET_PAGE_SIZE)) {
> +                    fprintf(stderr, "rdma migration: write error!\n");
> +                    qemu_file_set_error(f, -EIO);
> +                    return 0;
> +                }
> +
> +                /*
> +                 * do some polling
> +                 */
> +                while (1) {
> +                    ret = qemu_rdma_migration_poll(&rdma_mdata);
> +                    if (ret == QEMU_RDMA_MIGRATION_WRID_NONE) {
> +                        break;
> +                    }
> +                    if (ret < 0) {
> +                        fprintf(stderr, "rdma migration: polling error!\n");
> +                        qemu_file_set_error(f, -EIO);
> +                        return 0;
> +                    }
> +                }
> +                bytes_sent += TARGET_PAGE_SIZE;
>              }
>  
>              /* XBZRLE overflow or normal page */
> @@ -601,12 +656,15 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>      return 0;
>  }
>  
> +
> +int tprate = 1000;
> +
>  static int ram_save_iterate(QEMUFile *f, void *opaque)
>  {
>      int ret;
>      int i;
> -    int64_t t0;
> -    int total_sent = 0;
> +    int64_t t0, tp0;
> +    int total_sent = 0, last_total_sent = 0;
>  
>      qemu_mutex_lock_ramlist();
>  
> @@ -625,23 +683,55 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
>              break;
>          }
>          total_sent += bytes_sent;
> +        last_total_sent += bytes_sent;
>          acct_info.iterations++;
>          /* we want to check in the 1st loop, just in case it was the 1st time
>             and we had to sync the dirty bitmap.
>             qemu_get_clock_ns() is a bit expensive, so we only check each some
>             iterations
>          */
> +
> +        /*
> +         * RFC RDMA: Can we have something like this to periodically print
> +         * out throughput.
> +         * This is just a rough-sketch that partially worked for me.
> +         * I assume there a better way that everyone would prefer.
> +         * Perhaps we could set a QMP command that toggled a "periodic 
> printing"
> +         * option that allowed more details to be printed on stdout.....?
> +         */
>          if ((i & 63) == 0) {
> -            uint64_t t1 = (qemu_get_clock_ns(rt_clock) - t0) / 1000000;
> +            uint64_t curr = qemu_get_clock_ns(rt_clock);
> +            uint64_t t1 = (curr - t0) / 1000000;
> +            double tp;
>              if (t1 > MAX_WAIT) {
>                  DPRINTF("big wait: %" PRIu64 " milliseconds, %d 
> iterations\n",
>                          t1, i);
>                  break;
>              }
> +
> +            if ((i % tprate) == 0) {
> +                uint64_t tp1 = (curr - tp0) / 1000000;
> +                tp = ((double) last_total_sent * 8.0 /
> +                               ((double) tp1 / 1000.0)) / 1000.0 / 1000.0;
> +                printf("throughput: %f mbps\n", tp);
> +                last_total_sent = 0;
> +                tp0 = curr;
> +            }
>          }
>          i++;
>      }
>  
> +    /* flush buffer write */
> +    if (qemu_rdma_migration_enabled()) {
> +        int resp;
> +        resp = qemu_rdma_migration_write_flush(&rdma_mdata);
> +        if (resp < 0) {
> +            fprintf(stderr, "rdma migration: write flush error!\n");
> +            qemu_file_set_error(f, -EIO);
> +            return 0;
> +        }
> +    }
> +
>      qemu_mutex_unlock_ramlist();
>  
>      if (ret < 0) {
> @@ -863,6 +953,22 @@ static int ram_load(QEMUFile *f, void *opaque, int 
> version_id)
>                  ret = -EINVAL;
>                  goto done;
>              }
> +        } else if (flags & RAM_SAVE_FLAG_RDMA) {
> +            /*
> +             * RFC RDMA: This bad hack was to cause the loop break.
> +             *           Comments are welcome on how to get rid of it.
> +             *           Communicating here is unnecessary because the
> +             *           RDMA page has already arrived.
> +             *           Comments are welcome on how to get rif of this.
> +             */
> +            if (!qemu_rdma_migration_enabled()) {
> +                return -EINVAL;
> +            }
> +            void *host = host_from_stream_offset(f, addr, flags);
> +            if (!host) {
> +                return -EINVAL;
> +            }
> +            /* rdma page is already here, nothing to do */
>          }
>          error = qemu_file_get_error(f);
>          if (error) {
> diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
> index 68deefb..7c9968e 100644
> --- a/include/migration/qemu-file.h
> +++ b/include/migration/qemu-file.h
> @@ -112,6 +112,7 @@ int qemu_file_rate_limit(QEMUFile *f);
>  int64_t qemu_file_set_rate_limit(QEMUFile *f, int64_t new_rate);
>  int64_t qemu_file_get_rate_limit(QEMUFile *f);
>  int qemu_file_get_error(QEMUFile *f);
> +void qemu_file_set_error(QEMUFile *f, int ret);
>  
>  static inline void qemu_put_be64s(QEMUFile *f, const uint64_t *pv)
>  {
> diff --git a/savevm.c b/savevm.c
> index 304d1ef..071196e 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -24,6 +24,7 @@
>  
>  #include "config-host.h"
>  #include "qemu-common.h"
> +#include "qemu/rdma.h"
>  #include "hw/hw.h"
>  #include "hw/qdev.h"
>  #include "net/net.h"
> @@ -50,7 +51,7 @@
>  #define ARP_OP_REQUEST_REV 0x3
>  
>  static int announce_self_create(uint8_t *buf,
> -                             uint8_t *mac_addr)
> +                                uint8_t *mac_addr)
>  {
>      /* Ethernet header. */
>      memset(buf, 0xff, 6);         /* destination MAC addr */
> @@ -97,16 +98,16 @@ static void qemu_announce_self_once(void *opaque)
>          qemu_mod_timer(timer, qemu_get_clock_ms(rt_clock) +
>                         50 + (SELF_ANNOUNCE_ROUNDS - count - 1) * 100);
>      } else {
> -         qemu_del_timer(timer);
> -         qemu_free_timer(timer);
> +            qemu_del_timer(timer);
> +            qemu_free_timer(timer);
>      }
>  }
>  
>  void qemu_announce_self(void)
>  {
> -     static QEMUTimer *timer;
> -     timer = qemu_new_timer_ms(rt_clock, qemu_announce_self_once, &timer);
> -     qemu_announce_self_once(&timer);
> +        static QEMUTimer *timer;
> +        timer = qemu_new_timer_ms(rt_clock, qemu_announce_self_once, &timer);
> +        qemu_announce_self_once(&timer);
>  }
>  
>  /***********************************************************/
> @@ -299,8 +300,8 @@ QEMUFile *qemu_fdopen(int fd, const char *mode)
>      QEMUFileStdio *s;
>  
>      if (mode == NULL ||
> -     (mode[0] != 'r' && mode[0] != 'w') ||
> -     mode[1] != 'b' || mode[2] != 0) {
> +        (mode[0] != 'r' && mode[0] != 'w') ||
> +        mode[1] != 'b' || mode[2] != 0) {
>          fprintf(stderr, "qemu_fdopen: Argument validity check failed\n");
>          return NULL;
>      }
> @@ -342,8 +343,8 @@ QEMUFile *qemu_fopen(const char *filename, const char 
> *mode)
>      QEMUFileStdio *s;
>  
>      if (mode == NULL ||
> -     (mode[0] != 'r' && mode[0] != 'w') ||
> -     mode[1] != 'b' || mode[2] != 0) {
> +        (mode[0] != 'r' && mode[0] != 'w') ||
> +        mode[1] != 'b' || mode[2] != 0) {
>          fprintf(stderr, "qemu_fopen: Argument validity check failed\n");
>          return NULL;
>      }
> @@ -417,7 +418,7 @@ int qemu_file_get_error(QEMUFile *f)
>      return f->last_error;
>  }
>  
> -static void qemu_file_set_error(QEMUFile *f, int ret)
> +void qemu_file_set_error(QEMUFile *f, int ret)
>  {
>      if (f->last_error == 0) {
>          f->last_error = ret;
> @@ -1613,6 +1614,7 @@ int qemu_savevm_state_iterate(QEMUFile *f)
>  {
>      SaveStateEntry *se;
>      int ret = 1;
> +    static int first_time = 1;
>  
>      QTAILQ_FOREACH(se, &savevm_handlers, entry) {
>          if (!se->ops || !se->ops->save_live_iterate) {
> @@ -1643,8 +1645,36 @@ int qemu_savevm_state_iterate(QEMUFile *f)
>          }
>      }
>      if (ret != 0) {
> +#ifdef QEMU_RDMA_MIGRATION_EXTRA_SYNC
> +        /*
> +         * We use two "sync" infiniband messages happen during migration.
> +         * One at the beginning and one at the end, just to be thorough.
> +         * This is the first one.
> +         */
> +        if (first_time && qemu_rdma_migration_enabled()) {
> +            int r;
> +            first_time = 0;
> +            if (qemu_rdma_migration_post_send_sync(&rdma_mdata,
> +                        QEMU_RDMA_MIGRATION_WRID_SEND_EXTRA_SYNC)) {
> +                fprintf(stderr,
> +                        "rdma migration: error posting extra send sync!\n");
> +                return -EIO;
> +            }
> +
> +            r = qemu_rdma_migration_wait_for_wrid(&rdma_mdata,
> +                        QEMU_RDMA_MIGRATION_WRID_SEND_EXTRA_SYNC);
> +            if (r < 0) {
> +                fprintf(stderr,
> +                        "rdma migration: qemu_savevm_state_iterate"
> +                        " sync polling error!\n");
> +                return -EIO;
> +            }
> +        }
> +#endif
> +
>          return ret;
>      }
> +
>      ret = qemu_file_get_error(f);
>      if (ret != 0) {
>          qemu_savevm_state_cancel();
> @@ -1684,7 +1714,7 @@ int qemu_savevm_state_complete(QEMUFile *f)
>          int len;
>  
>          if ((!se->ops || !se->ops->save_state) && !se->vmsd) {
> -         continue;
> +            continue;
>          }
>          trace_savevm_section_start();
>          /* Section type */
> @@ -1703,8 +1733,32 @@ int qemu_savevm_state_complete(QEMUFile *f)
>          trace_savevm_section_end(se->section_id);
>      }
>  
> +    /*
> +     * We use two "sync" infiniband messages happen during migration.
> +     * One at the beginning and one at the end, just to be thorough.
> +     * This is the second one.
> +     */
> +    if (qemu_rdma_migration_enabled()) {
> +        if (qemu_rdma_migration_post_send_sync(&rdma_mdata,
> +                    QEMU_RDMA_MIGRATION_WRID_SEND_SYNC)) {
> +            fprintf(stderr, "rdma migration: error posting send sync!\n");
> +            return -EIO;
> +        }
> +    }
> +
>      qemu_put_byte(f, QEMU_VM_EOF);
>  
> +    /* wait for RDMA sync message to complete */
> +    if (qemu_rdma_migration_enabled()) {
> +        int ret = qemu_rdma_migration_wait_for_wrid(&rdma_mdata,
> +                QEMU_RDMA_MIGRATION_WRID_SEND_SYNC);
> +        if (ret < 0) {
> +            fprintf(stderr, "rdma migration: qemu_savevm_state_full"
> +                            " sync polling error!\n");
> +            return -EIO;
> +        }
> +     }
> +
>      return qemu_file_get_error(f);
>  }
>  
> @@ -2014,8 +2068,18 @@ int qemu_loadvm_state(QEMUFile *f)
>  
>      cpu_synchronize_all_post_init();
>  
> -    ret = 0;
> +    /* wait for RDMA sync message */
> +    if (qemu_rdma_migration_enabled()) {
> +        ret = qemu_rdma_migration_wait_for_wrid(&rdma_mdata,
> +                QEMU_RDMA_MIGRATION_WRID_RECV_SYNC);
> +        if (ret < 0) {
> +            fprintf(stderr, "rdma migration: qemu_loadvm_state_no_header"
> +                            " sync polling error!\n");
> +            goto out;
> +        }
> +    }
>  
> +    ret = 0;
>  out:
>      QLIST_FOREACH_SAFE(le, &loadvm_handlers, entry, new_le) {
>          QLIST_REMOVE(le, entry);
>