[Patch v2 0/6] migration/postcopy: enable compress during postcopy

[Patch v2 0/6] migration/postcopy: enable compress during postcopy

[Wei Yang]

This patch set tries enable compress during postcopy.

postcopy requires to place a whole host page, while migration thread migrate
memory in target page size. This makes postcopy need to collect all target
pages in one host page before placing via userfaultfd.

To enable compress during postcopy, there are two problems to solve:

    1. Random order for target page arrival
    2. Target pages in one host page arrives without interrupt by target
       page from other host page

The first one is handled by counting the number of target pages arrived
instead of the last target page arrived.

The second one is handled by:

    1. Flush compress thread for each host page
    2. Wait for decompress thread for before placing host page

With the combination of these two changes, compress is enabled during
postcopy.

---
v2:
     * use uintptr_t to calculate place_dest
     * check target pages belongs to the same host page

Wei Yang (6):
  migration/postcopy: reduce memset when it is zero page and
    matches_target_page_size
  migration/postcopy: wait for decompress thread in precopy
  migration/postcopy: count target page number to decide the
    place_needed
  migration/postcopy: set all_zero to true on the first target page
  migration/postcopy: enable random order target page arrival
  migration/postcopy: enable compress during postcopy

 migration/migration.c | 11 -------
 migration/ram.c       | 67 +++++++++++++++++++++++++++++++++----------
 2 files changed, 52 insertions(+), 26 deletions(-)

-- 
2.17.1

[Patch v2 1/6] migration/postcopy: reduce memset when it is zero page and matches_target_page_size

[Wei Yang]

In this case, page_buffer content would not be used.

Skip this to save some time.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/ram.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 99a98b2da4..7938a643d9 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4091,7 +4091,13 @@ static int ram_load_postcopy(QEMUFile *f)
         switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
         case RAM_SAVE_FLAG_ZERO:
             ch = qemu_get_byte(f);
-            memset(page_buffer, ch, TARGET_PAGE_SIZE);
+            /*
+             * Can skip to set page_buffer when
+             * this is a zero page and (block->page_size == TARGET_PAGE_SIZE).
+             */
+            if (ch || !matches_target_page_size) {
+                memset(page_buffer, ch, TARGET_PAGE_SIZE);
+            }
             if (ch) {
                 all_zero = false;
             }
-- 
2.17.1

[Patch v2 2/6] migration/postcopy: wait for decompress thread in precopy

[Wei Yang]

Compress is not supported with postcopy, it is safe to wait for
decompress thread just in precopy.

This is a preparation for later patch.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/ram.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 7938a643d9..f59e3fe197 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4375,6 +4375,7 @@ static int ram_load_precopy(QEMUFile *f)
         }
     }
 
+    ret |= wait_for_decompress_done();
     return ret;
 }
 
@@ -4406,8 +4407,6 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
         } else {
             ret = ram_load_precopy(f);
         }
-
-        ret |= wait_for_decompress_done();
     }
     trace_ram_load_complete(ret, seq_iter);
 
-- 
2.17.1

[Patch v2 3/6] migration/postcopy: count target page number to decide the place_needed

[Wei Yang]

In postcopy, it requires to place whole host page instead of target
page.

Currently, it relies on the page offset to decide whether this is the
last target page. We also can count the target page number during the
iteration. When the number of target page equals
(host page size / target page size), this means it is the last target
page in the host page.

This is a preparation for non-ordered target page transmission.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/ram.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index f59e3fe197..5c05376d8d 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4017,6 +4017,7 @@ static int ram_load_postcopy(QEMUFile *f)
     void *postcopy_host_page = mis->postcopy_tmp_page;
     void *last_host = NULL;
     bool all_zero = false;
+    int target_pages = 0;
 
     while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
         ram_addr_t addr;
@@ -4051,6 +4052,7 @@ static int ram_load_postcopy(QEMUFile *f)
                 ret = -EINVAL;
                 break;
             }
+            target_pages++;
             matches_target_page_size = block->page_size == TARGET_PAGE_SIZE;
             /*
              * Postcopy requires that we place whole host pages atomically;
@@ -4082,8 +4084,10 @@ static int ram_load_postcopy(QEMUFile *f)
              * If it's the last part of a host page then we place the host
              * page
              */
-            place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) &
-                                     (block->page_size - 1)) == 0;
+            if (target_pages == (block->page_size / TARGET_PAGE_SIZE)) {
+                place_needed = true;
+                target_pages = 0;
+            }
             place_source = postcopy_host_page;
         }
         last_host = host;
-- 
2.17.1

[Patch v2 4/6] migration/postcopy: set all_zero to true on the first target page

[Wei Yang]

For the first target page, all_zero is set to true for this round check.

After target_pages introduced, we could leverage this variable instead
of checking the address offset.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/ram.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 5c05376d8d..b5759793a9 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4067,7 +4067,7 @@ static int ram_load_postcopy(QEMUFile *f)
             page_buffer = postcopy_host_page +
                           ((uintptr_t)host & (block->page_size - 1));
             /* If all TP are zero then we can optimise the place */
-            if (!((uintptr_t)host & (block->page_size - 1))) {
+            if (target_pages == 1) {
                 all_zero = true;
             } else {
                 /* not the 1st TP within the HP */
-- 
2.17.1

[Patch v2 5/6] migration/postcopy: enable random order target page arrival

[Wei Yang]

After using number of target page received to track one host page, we
could have the capability to handle random order target page arrival in
one host page.

This is a preparation for enabling compress during postcopy.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

---
v2:
   * use uintptr_t to calculate place_dest
   * check target pages belongs to the same host page
---
 migration/ram.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index b5759793a9..666ad69284 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4015,7 +4015,7 @@ static int ram_load_postcopy(QEMUFile *f)
     MigrationIncomingState *mis = migration_incoming_get_current();
     /* Temporary page that is later 'placed' */
     void *postcopy_host_page = mis->postcopy_tmp_page;
-    void *last_host = NULL;
+    void *this_host = NULL;
     bool all_zero = false;
     int target_pages = 0;
 
@@ -4062,24 +4062,26 @@ static int ram_load_postcopy(QEMUFile *f)
              * that's moved into place later.
              * The migration protocol uses,  possibly smaller, target-pages
              * however the source ensures it always sends all the components
-             * of a host page in order.
+             * of a host page in one chunk.
              */
             page_buffer = postcopy_host_page +
                           ((uintptr_t)host & (block->page_size - 1));
             /* If all TP are zero then we can optimise the place */
             if (target_pages == 1) {
                 all_zero = true;
+                this_host = (void *)QEMU_ALIGN_DOWN((uintptr_t)host,
+                                                    block->page_size);
             } else {
                 /* not the 1st TP within the HP */
-                if (host != (last_host + TARGET_PAGE_SIZE)) {
-                    error_report("Non-sequential target page %p/%p",
-                                  host, last_host);
+                if (QEMU_ALIGN_DOWN((uintptr_t)host, block->page_size) !=
+                    (uintptr_t)this_host) {
+                    error_report("Non-same host page %p/%p",
+                                  host, this_host);
                     ret = -EINVAL;
                     break;
                 }
             }
 
-
             /*
              * If it's the last part of a host page then we place the host
              * page
@@ -4090,7 +4092,6 @@ static int ram_load_postcopy(QEMUFile *f)
             }
             place_source = postcopy_host_page;
         }
-        last_host = host;
 
         switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
         case RAM_SAVE_FLAG_ZERO:
@@ -4143,7 +4144,8 @@ static int ram_load_postcopy(QEMUFile *f)
 
         if (!ret && place_needed) {
             /* This gets called at the last target page in the host page */
-            void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
+            void *place_dest = (void *)QEMU_ALIGN_DOWN((uintptr_t)host,
+                                                       block->page_size);
 
             if (all_zero) {
                 ret = postcopy_place_page_zero(mis, place_dest,
-- 
2.17.1

[Patch v2 6/6] migration/postcopy: enable compress during postcopy

[Wei Yang]

postcopy requires to place a whole host page, while migration thread
migrate memory in target page size. This makes postcopy need to collect
all target pages in one host page before placing via userfaultfd.

To enable compress during postcopy, there are two problems to solve:

    1. Random order for target page arrival
    2. Target pages in one host page arrives without interrupt by target
       page from other host page

The first one is handled by previous cleanup patch.

This patch handles the second one by:

    1. Flush compress thread for each host page
    2. Wait for decompress thread for before placing host page

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/migration.c | 11 -----------
 migration/ram.c       | 28 +++++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 354ad072fa..3c926a3ae3 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1005,17 +1005,6 @@ static bool migrate_caps_check(bool *cap_list,
 #endif
 
     if (cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM]) {
-        if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) {
-            /* The decompression threads asynchronously write into RAM
-             * rather than use the atomic copies needed to avoid
-             * userfaulting.  It should be possible to fix the decompression
-             * threads for compatibility in future.
-             */
-            error_setg(errp, "Postcopy is not currently compatible "
-                       "with compression");
-            return false;
-        }
-
         /* This check is reasonably expensive, so only when it's being
          * set the first time, also it's only the destination that needs
          * special support.
diff --git a/migration/ram.c b/migration/ram.c
index 666ad69284..0d53786311 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3449,6 +3449,14 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
 
             rs->target_page_count += pages;
 
+            /*
+             * During postcopy, it is necessary to make sure one whole host
+             * page is sent in one chunk.
+             */
+            if (migrate_postcopy_ram()) {
+                flush_compressed_data(rs);
+            }
+
             /*
              * we want to check in the 1st loop, just in case it was the 1st
              * time and we had to sync the dirty bitmap.
@@ -4026,6 +4034,7 @@ static int ram_load_postcopy(QEMUFile *f)
         void *place_source = NULL;
         RAMBlock *block = NULL;
         uint8_t ch;
+        int len;
 
         addr = qemu_get_be64(f);
 
@@ -4043,7 +4052,8 @@ static int ram_load_postcopy(QEMUFile *f)
 
         trace_ram_load_postcopy_loop((uint64_t)addr, flags);
         place_needed = false;
-        if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE)) {
+        if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE |
+                     RAM_SAVE_FLAG_COMPRESS_PAGE)) {
             block = ram_block_from_stream(f, flags);
 
             host = host_from_ram_block_offset(block, addr);
@@ -4126,6 +4136,17 @@ static int ram_load_postcopy(QEMUFile *f)
                                          TARGET_PAGE_SIZE);
             }
             break;
+        case RAM_SAVE_FLAG_COMPRESS_PAGE:
+            all_zero = false;
+            len = qemu_get_be32(f);
+            if (len < 0 || len > compressBound(TARGET_PAGE_SIZE)) {
+                error_report("Invalid compressed data length: %d", len);
+                ret = -EINVAL;
+                break;
+            }
+            decompress_data_with_multi_threads(f, page_buffer, len);
+            break;
+
         case RAM_SAVE_FLAG_EOS:
             /* normal exit */
             multifd_recv_sync_main();
@@ -4137,6 +4158,11 @@ static int ram_load_postcopy(QEMUFile *f)
             break;
         }
 
+        /* Got the whole host page, wait for decompress before placing. */
+        if (place_needed) {
+            ret |= wait_for_decompress_done();
+        }
+
         /* Detect for any possible file errors */
         if (!ret && qemu_file_get_error(f)) {
             ret = qemu_file_get_error(f);
-- 
2.17.1

Re: [Patch v2 5/6] migration/postcopy: enable random order target page arrival

[Dr. David Alan Gilbert]

* Wei Yang (richardw.yang@linux.intel.com) wrote:
> After using number of target page received to track one host page, we
> could have the capability to handle random order target page arrival in
> one host page.
> 
> This is a preparation for enabling compress during postcopy.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

Yep, that's better

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


> ---
> v2:
>    * use uintptr_t to calculate place_dest
>    * check target pages belongs to the same host page
> ---
>  migration/ram.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index b5759793a9..666ad69284 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -4015,7 +4015,7 @@ static int ram_load_postcopy(QEMUFile *f)
>      MigrationIncomingState *mis = migration_incoming_get_current();
>      /* Temporary page that is later 'placed' */
>      void *postcopy_host_page = mis->postcopy_tmp_page;
> -    void *last_host = NULL;
> +    void *this_host = NULL;
>      bool all_zero = false;
>      int target_pages = 0;
>  
> @@ -4062,24 +4062,26 @@ static int ram_load_postcopy(QEMUFile *f)
>               * that's moved into place later.
>               * The migration protocol uses,  possibly smaller, target-pages
>               * however the source ensures it always sends all the components
> -             * of a host page in order.
> +             * of a host page in one chunk.
>               */
>              page_buffer = postcopy_host_page +
>                            ((uintptr_t)host & (block->page_size - 1));
>              /* If all TP are zero then we can optimise the place */
>              if (target_pages == 1) {
>                  all_zero = true;
> +                this_host = (void *)QEMU_ALIGN_DOWN((uintptr_t)host,
> +                                                    block->page_size);
>              } else {
>                  /* not the 1st TP within the HP */
> -                if (host != (last_host + TARGET_PAGE_SIZE)) {
> -                    error_report("Non-sequential target page %p/%p",
> -                                  host, last_host);
> +                if (QEMU_ALIGN_DOWN((uintptr_t)host, block->page_size) !=
> +                    (uintptr_t)this_host) {
> +                    error_report("Non-same host page %p/%p",
> +                                  host, this_host);
>                      ret = -EINVAL;
>                      break;
>                  }
>              }
>  
> -
>              /*
>               * If it's the last part of a host page then we place the host
>               * page
> @@ -4090,7 +4092,6 @@ static int ram_load_postcopy(QEMUFile *f)
>              }
>              place_source = postcopy_host_page;
>          }
> -        last_host = host;
>  
>          switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
>          case RAM_SAVE_FLAG_ZERO:
> @@ -4143,7 +4144,8 @@ static int ram_load_postcopy(QEMUFile *f)
>  
>          if (!ret && place_needed) {
>              /* This gets called at the last target page in the host page */
> -            void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
> +            void *place_dest = (void *)QEMU_ALIGN_DOWN((uintptr_t)host,
> +                                                       block->page_size);
>  
>              if (all_zero) {
>                  ret = postcopy_place_page_zero(mis, place_dest,
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Patch v2 5/6] migration/postcopy: enable random order target page arrival

[Wei Yang]

On Thu, Nov 07, 2019 at 02:30:25PM +0000, Dr. David Alan Gilbert wrote:
>* Wei Yang (richardw.yang@linux.intel.com) wrote:
>> After using number of target page received to track one host page, we
>> could have the capability to handle random order target page arrival in
>> one host page.
>> 
>> This is a preparation for enabling compress during postcopy.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>
>Yep, that's better
>
>Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>

Thanks for your suggestion :-)

-- 
Wei Yang
Help you, Help me

Re: [Patch v2 0/6] migration/postcopy: enable compress during postcopy

[Wei Yang]

Would this one be picked up in this version?

On Thu, Nov 07, 2019 at 08:39:01PM +0800, Wei Yang wrote:
>This patch set tries enable compress during postcopy.
>
>postcopy requires to place a whole host page, while migration thread migrate
>memory in target page size. This makes postcopy need to collect all target
>pages in one host page before placing via userfaultfd.
>
>To enable compress during postcopy, there are two problems to solve:
>
>    1. Random order for target page arrival
>    2. Target pages in one host page arrives without interrupt by target
>       page from other host page
>
>The first one is handled by counting the number of target pages arrived
>instead of the last target page arrived.
>
>The second one is handled by:
>
>    1. Flush compress thread for each host page
>    2. Wait for decompress thread for before placing host page
>
>With the combination of these two changes, compress is enabled during
>postcopy.
>
>---
>v2:
>     * use uintptr_t to calculate place_dest
>     * check target pages belongs to the same host page
>
>Wei Yang (6):
>  migration/postcopy: reduce memset when it is zero page and
>    matches_target_page_size
>  migration/postcopy: wait for decompress thread in precopy
>  migration/postcopy: count target page number to decide the
>    place_needed
>  migration/postcopy: set all_zero to true on the first target page
>  migration/postcopy: enable random order target page arrival
>  migration/postcopy: enable compress during postcopy
>
> migration/migration.c | 11 -------
> migration/ram.c       | 67 +++++++++++++++++++++++++++++++++----------
> 2 files changed, 52 insertions(+), 26 deletions(-)
>
>-- 
>2.17.1

-- 
Wei Yang
Help you, Help me

Re: [Patch v2 0/6] migration/postcopy: enable compress during postcopy

[Dr. David Alan Gilbert]

* Wei Yang (richardw.yang@linux.intel.com) wrote:
> Would this one be picked up in this version?

I think that one is on Juan's list for the pull he's going to do soon.

Dave


> On Thu, Nov 07, 2019 at 08:39:01PM +0800, Wei Yang wrote:
> >This patch set tries enable compress during postcopy.
> >
> >postcopy requires to place a whole host page, while migration thread migrate
> >memory in target page size. This makes postcopy need to collect all target
> >pages in one host page before placing via userfaultfd.
> >
> >To enable compress during postcopy, there are two problems to solve:
> >
> >    1. Random order for target page arrival
> >    2. Target pages in one host page arrives without interrupt by target
> >       page from other host page
> >
> >The first one is handled by counting the number of target pages arrived
> >instead of the last target page arrived.
> >
> >The second one is handled by:
> >
> >    1. Flush compress thread for each host page
> >    2. Wait for decompress thread for before placing host page
> >
> >With the combination of these two changes, compress is enabled during
> >postcopy.
> >
> >---
> >v2:
> >     * use uintptr_t to calculate place_dest
> >     * check target pages belongs to the same host page
> >
> >Wei Yang (6):
> >  migration/postcopy: reduce memset when it is zero page and
> >    matches_target_page_size
> >  migration/postcopy: wait for decompress thread in precopy
> >  migration/postcopy: count target page number to decide the
> >    place_needed
> >  migration/postcopy: set all_zero to true on the first target page
> >  migration/postcopy: enable random order target page arrival
> >  migration/postcopy: enable compress during postcopy
> >
> > migration/migration.c | 11 -------
> > migration/ram.c       | 67 +++++++++++++++++++++++++++++++++----------
> > 2 files changed, 52 insertions(+), 26 deletions(-)
> >
> >-- 
> >2.17.1
> 
> -- 
> Wei Yang
> Help you, Help me
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Patch v2 0/6] migration/postcopy: enable compress during postcopy

[Wei Yang]

On Wed, Dec 18, 2019 at 07:55:38PM +0000, Dr. David Alan Gilbert wrote:
>* Wei Yang (richardw.yang@linux.intel.com) wrote:
>> Would this one be picked up in this version?
>
>I think that one is on Juan's list for the pull he's going to do soon.
>
>Dave
>

Happy New Year to all~

May I ask the plan for this patch set?


-- 
Wei Yang
Help you, Help me

Re: [Patch v2 1/6] migration/postcopy: reduce memset when it is zero page and matches_target_page_size

[Juan Quintela]

Wei Yang <richardw.yang@linux.intel.com> wrote:
> In this case, page_buffer content would not be used.
>
> Skip this to save some time.
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Acked-by: Juan Quintela <quintela@redhat.com>

Re: [Patch v2 2/6] migration/postcopy: wait for decompress thread in precopy

[Juan Quintela]

Wei Yang <richardw.yang@linux.intel.com> wrote:
> Compress is not supported with postcopy, it is safe to wait for
> decompress thread just in precopy.
>
> This is a preparation for later patch.
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Re: [Patch v2 3/6] migration/postcopy: count target page number to decide the place_needed

[Juan Quintela]

Wei Yang <richardw.yang@linux.intel.com> wrote:
> In postcopy, it requires to place whole host page instead of target
> page.
>
> Currently, it relies on the page offset to decide whether this is the
> last target page. We also can count the target page number during the
> iteration. When the number of target page equals
> (host page size / target page size), this means it is the last target
> page in the host page.
>
> This is a preparation for non-ordered target page transmission.
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Re: [Patch v2 4/6] migration/postcopy: set all_zero to true on the first target page

[Juan Quintela]

Wei Yang <richardw.yang@linux.intel.com> wrote:
> For the first target page, all_zero is set to true for this round check.
>
> After target_pages introduced, we could leverage this variable instead
> of checking the address offset.
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Re: [Patch v2 5/6] migration/postcopy: enable random order target page arrival

[Juan Quintela]

Wei Yang <richardw.yang@linux.intel.com> wrote:
> After using number of target page received to track one host page, we
> could have the capability to handle random order target page arrival in
> one host page.
>
> This is a preparation for enabling compress during postcopy.
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>
> ---
> v2:
>    * use uintptr_t to calculate place_dest
>    * check target pages belongs to the same host page

Reviewed-by: Juan Quintela <quintela@redhat.com>

Re: [Patch v2 6/6] migration/postcopy: enable compress during postcopy

[Juan Quintela]

Wei Yang <richardw.yang@linux.intel.com> wrote:
> postcopy requires to place a whole host page, while migration thread
> migrate memory in target page size. This makes postcopy need to collect
> all target pages in one host page before placing via userfaultfd.
>
> To enable compress during postcopy, there are two problems to solve:
>
>     1. Random order for target page arrival
>     2. Target pages in one host page arrives without interrupt by target
>        page from other host page
>
> The first one is handled by previous cleanup patch.
>
> This patch handles the second one by:
>
>     1. Flush compress thread for each host page
>     2. Wait for decompress thread for before placing host page
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>