Re: [Qemu-devel] [PATCH 2/2] migration: do not overwrite zero pages

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/19/2013 08:10 PM, Paolo Bonzini wrote:
> Il 06/06/2013 10:36, Peter Lieven ha scritto:
>> on incoming migration do not memset pages to zero if they already read as zero.
>> this will allocate a new zero page and consume memory unnecessarily. even
>> if we madvise a MADV_DONTNEED later this will only deallocate the memory
>> asynchronously.
>>
>> Signed-off-by: Peter Lieven <pl@kamp.de>
>> ---
>>  arch_init.c |   14 ++++++++------
>>  1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch_init.c b/arch_init.c
>> index 283081d..642f241 100644
>> --- a/arch_init.c
>> +++ b/arch_init.c
>> @@ -821,14 +821,16 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
>>              }
>>  
>>              ch = qemu_get_byte(f);
>> -            memset(host, ch, TARGET_PAGE_SIZE);
>> +            if (ch != 0 || !is_zero_page(host)) {
>> +                memset(host, ch, TARGET_PAGE_SIZE);
>>  #ifndef _WIN32
>> -            if (ch == 0 &&
>> -                (!kvm_enabled() || kvm_has_sync_mmu()) &&
>> -                getpagesize() <= TARGET_PAGE_SIZE) {
>> -                qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
>> -            }
>> +                if (ch == 0 &&
>> +                    (!kvm_enabled() || kvm_has_sync_mmu()) &&
>> +                    getpagesize() <= TARGET_PAGE_SIZE) {
>> +                    qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
>> +                }
>>  #endif
>> +            }
>>          } else if (flags & RAM_SAVE_FLAG_PAGE) {
>>              void *host;
>>  
>>
> 
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Is it expected to reach upstream any time soon? Thanks.



-- 
Alexey