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[Qemu-devel] [PATCH v3 1/3] migration: API to clear bits of guest free pages from the dirty bitmap

Wei Wang posted 3 patches 7 years, 11 months ago
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[Qemu-devel] [PATCH v3 1/3] migration: API to clear bits of guest free pages from the dirty bitmap
Posted by Wei Wang 7 years, 11 months ago 
This patch adds an API to clear bits corresponding to guest free pages
from the dirty bitmap. Spilt the free page block if it crosses the QEMU
RAMBlock boundary.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Michael S. Tsirkin <mst@redhat.com>
---
 include/migration/misc.h |  2 ++
 migration/ram.c          | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/migration/misc.h b/include/migration/misc.h
index 77fd4f5..fae1acf 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -14,11 +14,13 @@
 #ifndef MIGRATION_MISC_H
 #define MIGRATION_MISC_H
 
+#include "exec/cpu-common.h"
 #include "qemu/notify.h"
 
 /* migration/ram.c */
 
 void ram_mig_init(void);
+void qemu_guest_free_page_hint(void *addr, size_t len);
 
 /* migration/block.c */
 
diff --git a/migration/ram.c b/migration/ram.c
index 5e33e5c..769a0f6 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2189,6 +2189,26 @@ static int ram_init_all(RAMState **rsp)
     return 0;
 }
 
+void qemu_guest_free_page_hint(void *addr, size_t len)
+{
+    RAMBlock *block;
+    ram_addr_t offset;
+    size_t used_len, start, npages;
+
+    for (used_len = len; len > 0; len -= used_len) {
+        block = qemu_ram_block_from_host(addr, false, &offset);
+        if (unlikely(offset + len > block->used_length)) {
+            used_len = block->used_length - offset;
+            addr += used_len;
+        }
+
+        start = offset >> TARGET_PAGE_BITS;
+        npages = used_len >> TARGET_PAGE_BITS;
+        bitmap_clear(block->bmap, start, npages);
+        ram_state->migration_dirty_pages -= npages;
+    }
+}
+
 /*
  * Each of ram_save_setup, ram_save_iterate and ram_save_complete has
  * long-running RCU critical section.  When rcu-reclaims in the code
-- 
1.8.3.1
Re: [Qemu-devel] [PATCH v3 1/3] migration: API to clear bits of guest free pages from the dirty bitmap
Posted by Dr. David Alan Gilbert 7 years, 11 months ago 
* Wei Wang (wei.w.wang@intel.com) wrote:
> This patch adds an API to clear bits corresponding to guest free pages
> from the dirty bitmap. Spilt the free page block if it crosses the QEMU
> RAMBlock boundary.
> 
> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
> CC: Juan Quintela <quintela@redhat.com>
> CC: Michael S. Tsirkin <mst@redhat.com>

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

> ---
>  include/migration/misc.h |  2 ++
>  migration/ram.c          | 20 ++++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/include/migration/misc.h b/include/migration/misc.h
> index 77fd4f5..fae1acf 100644
> --- a/include/migration/misc.h
> +++ b/include/migration/misc.h
> @@ -14,11 +14,13 @@
>  #ifndef MIGRATION_MISC_H
>  #define MIGRATION_MISC_H
>  
> +#include "exec/cpu-common.h"
>  #include "qemu/notify.h"
>  
>  /* migration/ram.c */
>  
>  void ram_mig_init(void);
> +void qemu_guest_free_page_hint(void *addr, size_t len);
>  
>  /* migration/block.c */
>  
> diff --git a/migration/ram.c b/migration/ram.c
> index 5e33e5c..769a0f6 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2189,6 +2189,26 @@ static int ram_init_all(RAMState **rsp)
>      return 0;
>  }
>  
> +void qemu_guest_free_page_hint(void *addr, size_t len)
> +{
> +    RAMBlock *block;
> +    ram_addr_t offset;
> +    size_t used_len, start, npages;
> +
> +    for (used_len = len; len > 0; len -= used_len) {
> +        block = qemu_ram_block_from_host(addr, false, &offset);
> +        if (unlikely(offset + len > block->used_length)) {
> +            used_len = block->used_length - offset;
> +            addr += used_len;
> +        }
> +
> +        start = offset >> TARGET_PAGE_BITS;
> +        npages = used_len >> TARGET_PAGE_BITS;
> +        bitmap_clear(block->bmap, start, npages);
> +        ram_state->migration_dirty_pages -= npages;
> +    }
> +}
> +
>  /*
>   * Each of ram_save_setup, ram_save_iterate and ram_save_complete has
>   * long-running RCU critical section.  When rcu-reclaims in the code
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
Re: [Qemu-devel] [PATCH v3 1/3] migration: API to clear bits of guest free pages from the dirty bitmap
Posted by Wei Wang 7 years, 11 months ago 
On 03/07/2018 08:23 PM, Dr. David Alan Gilbert wrote:
> * Wei Wang (wei.w.wang@intel.com) wrote:
>> This patch adds an API to clear bits corresponding to guest free pages
>> from the dirty bitmap. Spilt the free page block if it crosses the QEMU
>> RAMBlock boundary.
>>
>> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
>> CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> CC: Juan Quintela <quintela@redhat.com>
>> CC: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
>> ---
>>   include/migration/misc.h |  2 ++
>>   migration/ram.c          | 20 ++++++++++++++++++++
>>   2 files changed, 22 insertions(+)
>>
>> diff --git a/include/migration/misc.h b/include/migration/misc.h
>> index 77fd4f5..fae1acf 100644
>> --- a/include/migration/misc.h
>> +++ b/include/migration/misc.h
>> @@ -14,11 +14,13 @@
>>   #ifndef MIGRATION_MISC_H
>>   #define MIGRATION_MISC_H
>>   
>> +#include "exec/cpu-common.h"
>>   #include "qemu/notify.h"
>>   
>>   /* migration/ram.c */
>>   
>>   void ram_mig_init(void);
>> +void qemu_guest_free_page_hint(void *addr, size_t len);
>>   
>>   /* migration/block.c */
>>   
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 5e33e5c..769a0f6 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -2189,6 +2189,26 @@ static int ram_init_all(RAMState **rsp)
>>       return 0;
>>   }
>>   
>> +void qemu_guest_free_page_hint(void *addr, size_t len)
>> +{
>> +    RAMBlock *block;
>> +    ram_addr_t offset;
>> +    size_t used_len, start, npages;
>> +
>> +    for (used_len = len; len > 0; len -= used_len) {
>> +        block = qemu_ram_block_from_host(addr, false, &offset);
>> +        if (unlikely(offset + len > block->used_length)) {
>> +            used_len = block->used_length - offset;
>> +            addr += used_len;
>> +        }
>> +
>> +        start = offset >> TARGET_PAGE_BITS;
>> +        npages = used_len >> TARGET_PAGE_BITS;
>> +        bitmap_clear(block->bmap, start, npages);
>> +        ram_state->migration_dirty_pages -= npages;

Hi Dave,

Thanks for reviewing this patch. There will be a little more change here 
about calculating "ram_state->migration_dirty_pages" since we just 
extend this optimization to all the stages now (instead of just bulk 
stage). Please have a check more explanations at the v4 cover-letter 
ChangeLog.

Best,
Wei

Patchew 2.1-devel-b67e4c2

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