Re: [Qemu-devel] [PATCH 3/7] arch_init: add ram_madvise_free()

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

On 06/16/2013 12:04 PM, Anthony Liguori wrote:
> Lei Li <lilei@linux.vnet.ibm.com> writes:
>
>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>> ---
>>   arch_init.c                   |   13 +++++++++++++
>>   include/migration/migration.h |    3 +++
>>   2 files changed, 16 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch_init.c b/arch_init.c
>> index 872020e..fc66bd2 100644
>> --- a/arch_init.c
>> +++ b/arch_init.c
>> @@ -524,6 +524,19 @@ uint64_t ram_bytes_total(void)
>>       return total;
>>   }
>>   
>> +void ram_madvise_free(ram_addr_t size)
>> +{
>> +    void *ram;
>> +    RAMBlock *block = NULL;
>> +
>> +    ram = memory_region_get_ram_ptr(block->mr);
>> +
>> +    /* XXX. Here just simplely madvise(.., MADV_DONTNEED) the whole ram
>> +     * pages, need more work to keep MADV_DONTNEED ram pages that
>> +     * already sent. */
>> +    qemu_madvise(ram, size, MADV_DONTNEED);
>> +}
>> +
> I don't think this is right at all.  There's no guarantee we have a
> single linear mapping of all ram.
>
> I think you need something a bit more clever than this.
>
>>   static void migration_end(void)
>>   {
>>       if (migration_bitmap) {
>> diff --git a/include/migration/migration.h b/include/migration/migration.h
>> index 8866c3c..9cc5285 100644
>> --- a/include/migration/migration.h
>> +++ b/include/migration/migration.h
>> @@ -21,6 +21,7 @@
>>   #include "qapi/error.h"
>>   #include "migration/vmstate.h"
>>   #include "qapi-types.h"
>> +#include "exec/memory.h"
>>   
>>   enum {
>>       MIG_STATE_ERROR,
>> @@ -100,6 +101,8 @@ uint64_t ram_bytes_remaining(void);
>>   uint64_t ram_bytes_transferred(void);
>>   uint64_t ram_bytes_total(void);
>>   
>> +void ram_madvise_free(ram_addr_t size);
>> +
> If you introduce new interfaces, please include documentation in the
> header.
>
> Regards,
>
> Anthony Liguori
>
>>   extern SaveVMHandlers savevm_ram_handlers;
>>   
>>   uint64_t dup_mig_bytes_transferred(void);
>> -- 
>> 1.7.7.6
>

We have a new function in master...... ram_handle_compressed()  (was 
exported for RDMA).

Perhaps this could be used.....

- Michael