Re: [Qemu-devel] [PATCH] Add warmup phase for live migration of large memory apps

[Shribman, Aidan]

> -----Original Message-----
> From: Anthony Liguori [mailto:address@hidden 
> Sent: Wednesday, May 11, 2011 4:35 PM
> To: Shribman, Aidan
> Cc: address@hidden
> Subject: Re: [Qemu-devel] [PATCH] Add warmup phase for live 
> migration of large memory apps
> 
> On 05/11/2011 02:58 AM, Shribman, Aidan wrote:
> > From: Aidan Shribman<address@hidden>
> >
> > [PATCH] Add warmup phase for live migration of large memory apps
> >
> > By invoking "migrate -w<url>" we initiate a background 
> live-migration
> > transferring of dirty pages continuously until invocation 
> of "migrate_end"
> > which attempts to complete the live migration operation.
> >
> > Qemu host: Ubuntu 10.10
> >
> > Testing: live migration (with/without warmup phase) tested 
> successfully.
> >
> > Signed-off-by: Benoit Hudzia<address@hidden>
> > Signed-off-by: Petter Svard<address@hidden>
> > Signed-off-by: Aidan Shribman<address@hidden>
> 
> If you do:
> 
> migrate_set_downtime 0
> migrate -d <url>
> 
> You'll achieve the same result.  The migration will never converge 
> because there's no way QEMU can meet the downtime expectation.

If there are no additional dirty pages to be sent i.e. ram_save_remaining() == 
0 then the migration *will* converge (even though we don't want it to) see:

int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
{       
    ...
    expected_time = ram_save_remaining() * TARGET_PAGE_SIZE / bwidth;
    return (stage == 2) && (expected_time <= migrate_max_downtime());
}

So using migrate_set_downtime appears to be only a partial surrogate for 
"migrate -x <url>" and "migrate_end"

Thanks,
Aidan Shribman

> 
> You can then do:
> 
> migrate_set_downtime 30ms
> 
> To let migration go.  You can even use info migrate to figure 
> out when 
> migration has been sufficiently warmed up.
> 
> You can also always do migrate_cancel to abort the operation.
> 
> Regards,
> 
> Anthony Liguori
> 
> > ---
> >   hmp-commands.hx |   34 +++++++++++++++++++++++++---------
> >   migration.c     |   23 ++++++++++++++++++++++-
> >   migration.h     |    2 ++
> >   qmp-commands.hx |   41 ++++++++++++++++++++++++++++++++++-------
> >   savevm.c        |   12 ++++++++++++
> >   sysemu.h        |    1 +
> >   6 files changed, 96 insertions(+), 17 deletions(-)
> >
> > diff --git a/hmp-commands.hx b/hmp-commands.hx
> > index e5585ba..234a952 100644
> > --- a/hmp-commands.hx
> > +++ b/hmp-commands.hx
> > @@ -717,24 +717,27 @@ ETEXI
> >
> >       {
> >           .name       = "migrate",
> > -        .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
> > -        .params     = "[-d] [-b] [-i] uri",
> > -        .help       = "migrate to URI (using -d to not 
> wait for completion)"
> > -                 "\n\t\t\t -b for migration without shared 
> storage with"
> > -                 " full copy of disk\n\t\t\t -i for 
> migration without "
> > -                 "shared storage with incremental copy of disk "
> > -                 "(base image shared between src and destination)",
> > +        .args_type  = "detach:-d,blk:-b,inc:-i,warmup:-w,uri:s",
> > +        .params     = "[-d] [-b] [-i] [-w] uri",
> > +        .help       = "migrate to URI"
> > +                      "\n\t -d to not wait for completion"
> > +                      "\n\t -b for migration without 
> shared storage with"
> > +                      " full copy of disk"
> > +                      "\n\t -i for migration without"
> > +                      " shared storage with incremental 
> copy of disk"
> > +                      " (base image shared between source 
> and destination)"
> > +                      "\n\t -w to enter warmup phase",
> >           .user_print = monitor_user_noop,  
> >     .mhandler.cmd_new = do_migrate,
> >       },
> >
> > -
> >   STEXI
> > address@hidden migrate [-d] [-b] [-i] @var{uri}
> > address@hidden migrate [-d] [-b] [-i] [-w] @var{uri}
> >   @findex migrate
> >   Migrate to @var{uri} (using -d to not wait for completion).
> >     -b for migration with full copy of disk
> >     -i for migration with incremental copy of disk (base 
> image is shared)
> > +    -w to enter warmup phase
> >   ETEXI
> >
> >       {
> > @@ -753,6 +756,19 @@ Cancel the current VM migration.
> >   ETEXI
> >
> >       {
> > +        .name       = "migrate_end",
> > +        .args_type  = "",
> > +        .params     = "",
> > +        .help       = "Complete warmup and move to full 
> live migration",
> > +        .mhandler.cmd = do_migrate_end,
> > +    },
> > +
> > +STEXI
> > address@hidden migrate_end
> > +Complete warmup and move to full live migration.
> > +ETEXI
> > +
> > +    {
> >           .name       = "migrate_set_speed",
> >           .args_type  = "value:o",
> >           .params     = "value",
> > diff --git a/migration.c b/migration.c
> > index 9ee8b17..7525b47 100644
> > --- a/migration.c
> > +++ b/migration.c
> > @@ -31,6 +31,8 @@
> >       do { } while (0)
> >   #endif
> >
> > +static int is_migrate_warmup = 0;
> > +
> >   /* Migration speed throttling */
> >   static uint32_t max_throttle = (32<<  20);
> >
> > @@ -81,6 +83,11 @@ int do_migrate(Monitor *mon, const QDict 
> *qdict, QObject **ret_data)
> >       int blk = qdict_get_try_bool(qdict, "blk", 0);
> >       int inc = qdict_get_try_bool(qdict, "inc", 0);
> >       const char *uri = qdict_get_str(qdict, "uri");
> > +    is_migrate_warmup = qdict_get_try_bool(qdict, "warmup", 0);
> > +
> > +    if (is_migrate_warmup) {
> > +        detach = 1; /* as we need migrate_end to complte */
> > +   }
> >
> >       if (current_migration&&
> >           current_migration->get_status(current_migration) 
> == MIG_STATE_ACTIVE) {
> > @@ -361,7 +368,9 @@ void migrate_fd_put_ready(void *opaque)
> >       }
> >
> >       DPRINTF("iterate\n");
> > -    if (qemu_savevm_state_iterate(s->mon, s->file) == 1) {
> > +    if (is_migrate_warmup) {
> > +            qemu_savevm_state_warmup(s->mon, s->file);
> > +   } else if (qemu_savevm_state_iterate(s->mon, s->file) == 1) {
> >           int state;
> >           int old_vm_running = vm_running;
> >
> > @@ -448,3 +457,15 @@ int migrate_fd_close(void *opaque)
> >       qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
> >       return s->close(s);
> >   }
> > +
> > +void do_migrate_end(Monitor *mon, const QDict *qdict)
> > +{
> > +    if (!vm_running) {
> > +        return;
> > +   }
> > +    if (!is_migrate_warmup) {
> > +        return;
> > +   }
> > +    is_migrate_warmup = 0;
> > +}
> > +
> > diff --git a/migration.h b/migration.h
> > index d13ed4f..6a96b29 100644
> > --- a/migration.h
> > +++ b/migration.h
> > @@ -134,4 +134,6 @@ static inline FdMigrationState 
> *migrate_to_fms(MigrationState *mig_state)
> >       return container_of(mig_state, FdMigrationState, mig_state);
> >   }
> >
> > +void do_migrate_end(Monitor *mon, const QDict *qdict);
> > +
> >   #endif
> > diff --git a/qmp-commands.hx b/qmp-commands.hx
> > index 793cf1c..58fe696 100644
> > --- a/qmp-commands.hx
> > +++ b/qmp-commands.hx
> > @@ -431,13 +431,16 @@ EQMP
> >
> >       {
> >           .name       = "migrate",
> > -        .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
> > -        .params     = "[-d] [-b] [-i] uri",
> > -        .help       = "migrate to URI (using -d to not 
> wait for completion)"
> > -                 "\n\t\t\t -b for migration without shared 
> storage with"
> > -                 " full copy of disk\n\t\t\t -i for 
> migration without "
> > -                 "shared storage with incremental copy of disk "
> > -                 "(base image shared between src and destination)",
> > +        .args_type  = 
> "detach:-d,blk:-b,inc:-i,xbrle:-x,warmup:-w,uri:s",
> > +        .params     = "[-d] [-b] [-i] [-w] uri",
> > +        .help       = "migrate to URI"
> > +                      "\n\t -d to not wait for completion"
> > +                      "\n\t -b for migration without 
> shared storage with"
> > +                      " full copy of disk"
> > +                      "\n\t -i for migration without"
> > +                      " shared storage with incremental 
> copy of disk"
> > +                      " (base image shared between source 
> and destination)"
> > +                      "\n\t -w to enter warmup phase",
> >           .user_print = monitor_user_noop,  
> >     .mhandler.cmd_new = do_migrate,
> >       },
> > @@ -453,6 +456,7 @@ Arguments:
> >   - "blk": block migration, full disk copy (json-bool, optional)
> >   - "inc": incremental disk copy (json-bool, optional)
> >   - "uri": Destination URI (json-string)
> > +- "warmup":to enter warmup phasen
> >
> >   Example:
> >
> > @@ -494,6 +498,29 @@ Example:
> >   EQMP
> >
> >       {
> > +        .name       = "migrate_end",
> > +        .args_type  = "",
> > +        .params     = "",
> > +        .help       = "Complete warmup and move to full 
> live migration",
> > +        .mhandler.cmd = do_migrate_end,
> > +    },
> > +
> > +SQMP
> > +migrate_end
> > +-----------
> > +
> > +End the current migration warmup.
> > +
> > +Arguments: None.
> > +
> > +Example:
> > +
> > +->  { "execute": "migrate_end" }
> > +<- { "return": {} }
> > +
> > +EQMP
> > +
> > +    {
> >           .name       = "migrate_set_speed",
> >           .args_type  = "value:f",
> >           .params     = "value",
> > diff --git a/savevm.c b/savevm.c
> > index 4e49765..521589c 100644
> > --- a/savevm.c
> > +++ b/savevm.c
> > @@ -1471,6 +1471,18 @@ int qemu_savevm_state_begin(Monitor 
> *mon, QEMUFile *f, int blk_enable,
> >       return 0;
> >   }
> >
> > +int qemu_savevm_state_warmup(Monitor *mon, QEMUFile *f) {
> > +    int ret = 1;
> > +
> > +    ret = qemu_savevm_state_iterate(mon, f);
> > +
> > +    if (ret == -EIO) {
> > +        return ret;
> > +   }
> > +
> > +    return 0;
> > +}
> > +
> >   int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f)
> >   {
> >       SaveStateEntry *se;
> > diff --git a/sysemu.h b/sysemu.h
> > index b81a70e..74e8a48 100644
> > --- a/sysemu.h
> > +++ b/sysemu.h
> > @@ -76,6 +76,7 @@ void main_loop_wait(int nonblocking);
> >   int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, 
> int blk_enable,
> >                               int shared);
> >   int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f);
> > +int qemu_savevm_state_warmup(Monitor *mon, QEMUFile *f);
> >   int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f);
> >   void qemu_savevm_state_cancel(Monitor *mon, QEMUFile *f);
> >   int qemu_loadvm_state(QEMUFile *f);
> 
>