Re: [Qemu-devel] [PATCH v6 21/28] migration: setup ramstate for resume
On Wed, Feb 14, 2018 at 06:40:46PM +, Dr. David Alan Gilbert wrote:
> * Peter Xu (pet...@redhat.com) wrote:
> > On Tue, Feb 13, 2018 at 06:17:51PM +, Dr. David Alan Gilbert wrote:
> > > * Peter Xu (pet...@redhat.com) wrote:
> > > > After we updated the dirty bitmaps of ramblocks, we also need to update
> > > > the critical fields in RAMState to make sure it is ready for a resume.
> > > >
> > > > Signed-off-by: Peter Xu
> > > > ---
> > > > migration/ram.c| 40 +++-
> > > > migration/trace-events | 1 +
> > > > 2 files changed, 40 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/migration/ram.c b/migration/ram.c
> > > > index a2a4b05d5c..d275875f54 100644
> > > > --- a/migration/ram.c
> > > > +++ b/migration/ram.c
> > > > @@ -2250,6 +2250,36 @@ static int ram_init_all(RAMState **rsp)
> > > > return 0;
> > > > }
> > > >
> > > > +static void ram_state_resume_prepare(RAMState *rs, QEMUFile *out)
> > > > +{
> > > > +RAMBlock *block;
> > > > +long pages = 0;
> > > > +
> > > > +/*
> > > > + * Postcopy is not using xbzrle/compression, so no need for that.
> > > > + * Also, since source are already halted, we don't need to care
> > > > + * about dirty page logging as well.
> > > > + */
> > > > +
> > > > +RAMBLOCK_FOREACH(block) {
> > > > +pages += bitmap_count_one(block->bmap,
> > > > + block->used_length >>
> > > > TARGET_PAGE_BITS);
> > > > +}
> > > > +
> > > > +/* This may not be aligned with current bitmaps. Recalculate. */
> > > > +rs->migration_dirty_pages = pages;
> > >
> > > migration_dirty_pages is uint64_t - so we should probably do the cast
> > > above and keep 'pages' as uint64_t.
> >
> > Sure.
> >
> > >
> > > > +rs->last_seen_block = NULL;
> > > > +rs->last_sent_block = NULL;
> > > > +rs->last_page = 0;
> > > > +rs->last_version = ram_list.version;
> > >
> > > Do you need to explicitly set
> > >rs->ram_bulk_stage = false;
> > >
> > > if the failure happened just after the start of postcopy and no
> > > requested pages had been sent, I think it might still be set?
> >
> > Could you elaborate what would go wrong even if it's still set?
>
> I think it might start sending all pages rather than just those
> that are dirty/needed; see migration_bitmap_find_dirty.
Ah yes. I should turn it off.
--
Peter Xu
Re: [Qemu-devel] [PATCH v6 21/28] migration: setup ramstate for resume
* Peter Xu (pet...@redhat.com) wrote:
> On Tue, Feb 13, 2018 at 06:17:51PM +, Dr. David Alan Gilbert wrote:
> > * Peter Xu (pet...@redhat.com) wrote:
> > > After we updated the dirty bitmaps of ramblocks, we also need to update
> > > the critical fields in RAMState to make sure it is ready for a resume.
> > >
> > > Signed-off-by: Peter Xu
> > > ---
> > > migration/ram.c| 40 +++-
> > > migration/trace-events | 1 +
> > > 2 files changed, 40 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/migration/ram.c b/migration/ram.c
> > > index a2a4b05d5c..d275875f54 100644
> > > --- a/migration/ram.c
> > > +++ b/migration/ram.c
> > > @@ -2250,6 +2250,36 @@ static int ram_init_all(RAMState **rsp)
> > > return 0;
> > > }
> > >
> > > +static void ram_state_resume_prepare(RAMState *rs, QEMUFile *out)
> > > +{
> > > +RAMBlock *block;
> > > +long pages = 0;
> > > +
> > > +/*
> > > + * Postcopy is not using xbzrle/compression, so no need for that.
> > > + * Also, since source are already halted, we don't need to care
> > > + * about dirty page logging as well.
> > > + */
> > > +
> > > +RAMBLOCK_FOREACH(block) {
> > > +pages += bitmap_count_one(block->bmap,
> > > + block->used_length >>
> > > TARGET_PAGE_BITS);
> > > +}
> > > +
> > > +/* This may not be aligned with current bitmaps. Recalculate. */
> > > +rs->migration_dirty_pages = pages;
> >
> > migration_dirty_pages is uint64_t - so we should probably do the cast
> > above and keep 'pages' as uint64_t.
>
> Sure.
>
> >
> > > +rs->last_seen_block = NULL;
> > > +rs->last_sent_block = NULL;
> > > +rs->last_page = 0;
> > > +rs->last_version = ram_list.version;
> >
> > Do you need to explicitly set
> >rs->ram_bulk_stage = false;
> >
> > if the failure happened just after the start of postcopy and no
> > requested pages had been sent, I think it might still be set?
>
> Could you elaborate what would go wrong even if it's still set?
I think it might start sending all pages rather than just those
that are dirty/needed; see migration_bitmap_find_dirty.
Dave
> Thanks,
>
> --
> Peter Xu
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
Re: [Qemu-devel] [PATCH v6 21/28] migration: setup ramstate for resume
On Tue, Feb 13, 2018 at 06:17:51PM +, Dr. David Alan Gilbert wrote:
> * Peter Xu (pet...@redhat.com) wrote:
> > After we updated the dirty bitmaps of ramblocks, we also need to update
> > the critical fields in RAMState to make sure it is ready for a resume.
> >
> > Signed-off-by: Peter Xu
> > ---
> > migration/ram.c| 40 +++-
> > migration/trace-events | 1 +
> > 2 files changed, 40 insertions(+), 1 deletion(-)
> >
> > diff --git a/migration/ram.c b/migration/ram.c
> > index a2a4b05d5c..d275875f54 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -2250,6 +2250,36 @@ static int ram_init_all(RAMState **rsp)
> > return 0;
> > }
> >
> > +static void ram_state_resume_prepare(RAMState *rs, QEMUFile *out)
> > +{
> > +RAMBlock *block;
> > +long pages = 0;
> > +
> > +/*
> > + * Postcopy is not using xbzrle/compression, so no need for that.
> > + * Also, since source are already halted, we don't need to care
> > + * about dirty page logging as well.
> > + */
> > +
> > +RAMBLOCK_FOREACH(block) {
> > +pages += bitmap_count_one(block->bmap,
> > + block->used_length >> TARGET_PAGE_BITS);
> > +}
> > +
> > +/* This may not be aligned with current bitmaps. Recalculate. */
> > +rs->migration_dirty_pages = pages;
>
> migration_dirty_pages is uint64_t - so we should probably do the cast
> above and keep 'pages' as uint64_t.
Sure.
>
> > +rs->last_seen_block = NULL;
> > +rs->last_sent_block = NULL;
> > +rs->last_page = 0;
> > +rs->last_version = ram_list.version;
>
> Do you need to explicitly set
>rs->ram_bulk_stage = false;
>
> if the failure happened just after the start of postcopy and no
> requested pages had been sent, I think it might still be set?
Could you elaborate what would go wrong even if it's still set?
Thanks,
--
Peter Xu
Re: [Qemu-devel] [PATCH v6 21/28] migration: setup ramstate for resume
* Peter Xu (pet...@redhat.com) wrote:
> After we updated the dirty bitmaps of ramblocks, we also need to update
> the critical fields in RAMState to make sure it is ready for a resume.
>
> Signed-off-by: Peter Xu
> ---
> migration/ram.c| 40 +++-
> migration/trace-events | 1 +
> 2 files changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index a2a4b05d5c..d275875f54 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2250,6 +2250,36 @@ static int ram_init_all(RAMState **rsp)
> return 0;
> }
>
> +static void ram_state_resume_prepare(RAMState *rs, QEMUFile *out)
> +{
> +RAMBlock *block;
> +long pages = 0;
> +
> +/*
> + * Postcopy is not using xbzrle/compression, so no need for that.
> + * Also, since source are already halted, we don't need to care
> + * about dirty page logging as well.
> + */
> +
> +RAMBLOCK_FOREACH(block) {
> +pages += bitmap_count_one(block->bmap,
> + block->used_length >> TARGET_PAGE_BITS);
> +}
> +
> +/* This may not be aligned with current bitmaps. Recalculate. */
> +rs->migration_dirty_pages = pages;
migration_dirty_pages is uint64_t - so we should probably do the cast
above and keep 'pages' as uint64_t.
> +rs->last_seen_block = NULL;
> +rs->last_sent_block = NULL;
> +rs->last_page = 0;
> +rs->last_version = ram_list.version;
Do you need to explicitly set
rs->ram_bulk_stage = false;
if the failure happened just after the start of postcopy and no
requested pages had been sent, I think it might still be set?
> +/* Update RAMState cache of output QEMUFile */
> +rs->f = out;
> +
> +trace_ram_state_resume_prepare(pages);
> +}
> +
> /*
> * Each of ram_save_setup, ram_save_iterate and ram_save_complete has
> * long-running RCU critical section. When rcu-reclaims in the code
> @@ -3178,8 +3208,16 @@ out:
> static int ram_resume_prepare(MigrationState *s, void *opaque)
> {
> RAMState *rs = *(RAMState **)opaque;
> +int ret;
>
> -return ram_dirty_bitmap_sync_all(s, rs);
> +ret = ram_dirty_bitmap_sync_all(s, rs);
> +if (ret) {
> +return ret;
> +}
> +
> +ram_state_resume_prepare(rs, s->to_dst_file);
> +
> +return 0;
> }
>
> static SaveVMHandlers savevm_ram_handlers = {
> diff --git a/migration/trace-events b/migration/trace-events
> index 45b1d89217..f5913ff51c 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -88,6 +88,7 @@ ram_dirty_bitmap_reload_complete(char *str) "%s"
> ram_dirty_bitmap_sync_start(void) ""
> ram_dirty_bitmap_sync_wait(void) ""
> ram_dirty_bitmap_sync_complete(void) ""
> +ram_state_resume_prepare(long v) "%ld"
>
> # migration/migration.c
> await_return_path_close_on_source_close(void) ""
Dave
> --
> 2.14.3
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
