Re: kvm userspace: ksm support

[Izik Eidus <ieidus@redhat.com>]

Anthony Liguori wrote:
> Izik Eidus wrote:
>> This patch is not for inclusion just rfc.
>>   
>
> The madvise() interface looks really nice :-)
>> Thanks.
>>
>>
>> From 1297b86aa257100b3d819df9f9f0932bf4f7f49d Mon Sep 17 00:00:00 2001
>> From: Izik Eidus <ieidus@redhat.com>
>> Date: Tue, 28 Jul 2009 19:14:26 +0300
>> Subject: [PATCH] kvm userspace: ksm support
>>
>> rfc for ksm support to kvm userpsace.
>>
>> thanks
>>
>> Signed-off-by: Izik Eidus <ieidus@redhat.com>
>> ---
>>  exec.c |    3 +++
>>  1 files changed, 3 insertions(+), 0 deletions(-)
>>
>> diff --git a/exec.c b/exec.c
>> index f6d9ec9..375cc18 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -2595,6 +2595,9 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
>>      new_block->host = file_ram_alloc(size, mem_path);
>>      if (!new_block->host) {
>>          new_block->host = qemu_vmalloc(size);
>> +#ifdef MADV_MERGEABLE
>> +        madvise(new_block->host, size, MADV_MERGEABLE);
>> +#endif
>>   
>
> Are madvise calls additive?
>
> Do we need to change the madvise balloon calls to include 
> MADV_MERGEABLE or will this carry the property forever?

You mean: when we later call for other madvise calls, if it will remove 
the MADV_MERGEABLE from that memory?
if yes, the answer is no, it should be still l left in the vma->vm_flags...

>
> I'd suggest doing the following in osdep.h too:
>
> #if !defined(MADV_MERGABLE)
> #define MADV_MERGABLE MADV_NORMAL
> #endif
>
> To avoid #ifdefs in .c files.

I tried to follow the way DONTFORK madvise is working...

So you say, just to throw this thing into osdep.h instead of that c file?

>
> Regards,
>
> Anthony Liguori
>
>>      }
>>      new_block->offset = last_ram_offset;
>>      new_block->length = size;
>>   
>