[v3] Migration: Transmit and detect zero pages in the multifd threads

[PATCH v3 23/23] migration: Use multifd before we check for the zero page

Posted by Juan Quintela 4 years, 2 months ago

So we use multifd to transmit zero pages.

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/ram.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 57efa67f20..3ae094f653 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2138,6 +2138,17 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
     ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS;
     int res;
 
+    /*
+     * Do not use multifd for:
+     * 1. Compression as the first page in the new block should be posted out
+     *    before sending the compressed page
+     * 2. In postcopy as one whole host page should be placed
+     */
+    if (!save_page_use_compression(rs) && migrate_use_multifd()
+        && !migration_in_postcopy()) {
+        return ram_save_multifd_page(rs, block, offset);
+    }
+
     if (control_save_page(rs, block, offset, &res)) {
         return res;
     }
@@ -2160,17 +2171,6 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
         return res;
     }
 
-    /*
-     * Do not use multifd for:
-     * 1. Compression as the first page in the new block should be posted out
-     *    before sending the compressed page
-     * 2. In postcopy as one whole host page should be placed
-     */
-    if (!save_page_use_compression(rs) && migrate_use_multifd()
-        && !migration_in_postcopy()) {
-        return ram_save_multifd_page(rs, block, offset);
-    }
-
     return ram_save_page(rs, pss, last_stage);
 }
 
-- 
2.33.1

Re: [PATCH v3 23/23] migration: Use multifd before we check for the zero page

Posted by Dr. David Alan Gilbert 4 years, 2 months ago

* Juan Quintela (quintela@redhat.com) wrote:
> So we use multifd to transmit zero pages.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/ram.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 57efa67f20..3ae094f653 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2138,6 +2138,17 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
>      ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS;
>      int res;
>  
> +    /*
> +     * Do not use multifd for:
> +     * 1. Compression as the first page in the new block should be posted out
> +     *    before sending the compressed page
> +     * 2. In postcopy as one whole host page should be placed
> +     */
> +    if (!save_page_use_compression(rs) && migrate_use_multifd()
> +        && !migration_in_postcopy()) {
> +        return ram_save_multifd_page(rs, block, offset);
> +    }
> +
>      if (control_save_page(rs, block, offset, &res)) {
>          return res;
>      }

Although I don't think it currently matters, I think that should be
after the control_save_page.

Dave

> @@ -2160,17 +2171,6 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
>          return res;
>      }
>  
> -    /*
> -     * Do not use multifd for:
> -     * 1. Compression as the first page in the new block should be posted out
> -     *    before sending the compressed page
> -     * 2. In postcopy as one whole host page should be placed
> -     */
> -    if (!save_page_use_compression(rs) && migrate_use_multifd()
> -        && !migration_in_postcopy()) {
> -        return ram_save_multifd_page(rs, block, offset);
> -    }
> -
>      return ram_save_page(rs, pss, last_stage);
>  }
>  
> -- 
> 2.33.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [PATCH v3 23/23] migration: Use multifd before we check for the zero page

Posted by Juan Quintela 4 years, 2 months ago

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
>> So we use multifd to transmit zero pages.
>> 
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> ---
>>  migration/ram.c | 22 +++++++++++-----------
>>  1 file changed, 11 insertions(+), 11 deletions(-)
>> 
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 57efa67f20..3ae094f653 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -2138,6 +2138,17 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
>>      ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS;
>>      int res;
>>  
>> +    /*
>> +     * Do not use multifd for:
>> +     * 1. Compression as the first page in the new block should be posted out
>> +     *    before sending the compressed page
>> +     * 2. In postcopy as one whole host page should be placed
>> +     */
>> +    if (!save_page_use_compression(rs) && migrate_use_multifd()
>> +        && !migration_in_postcopy()) {
>> +        return ram_save_multifd_page(rs, block, offset);
>> +    }
>> +
>>      if (control_save_page(rs, block, offset, &res)) {
>>          return res;
>>      }
>
> Although I don't think it currently matters, I think that should be
> after the control_save_page.

This needs to be improved to be compatible with old versions.

But .... if we don't care about RDMA, why do we care about
control_save_page()?

Later, Juan.