Re: [Qemu-devel] [PATCH v3] memory: reduce heap Rss size around 3M

[Zhong, Yang]

Hello Paolo&peter,

Maybe below patch is much more better, I also did the verification. Please all 
of you give some comments, many thanks!

diff --git a/memory.c b/memory.c
index 64b0a60..230f2cb 100644
--- a/memory.c
+++ b/memory.c
@@ -2422,7 +2422,7 @@ AddressSpace *address_space_init_shareable(MemoryRegion 
*root, const char *name)
     AddressSpace *as;

     QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) {
-        if (root == as->root && as->malloced) {
+        if (root == as->root && (as->malloced || as == &address_space_memory)) 
{
             as->ref_count++;
             return as;
         }

Regards,

ZhongYang

-----Original Message-----
From: Paolo Bonzini [mailto:address@hidden 
Sent: Wednesday, March 15, 2017 4:13 PM
To: Zhong, Yang <address@hidden>; address@hidden
Cc: Xu, Anthony <address@hidden>; Peter Maydell <address@hidden>
Subject: Re: [PATCH v3] memory: reduce heap Rss size around 3M



On 15/03/2017 14:39, Yang Zhong wrote:
> Since cpu-memory and memory have same address space,one malloced 
> memory is enough. This patch will skip memory malloc for memory 
> address space,which will reduce around 3M physical memory in heap.
> 
> Signed-off-by: Yang Zhong <address@hidden>
> ---
>  memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/memory.c b/memory.c
> index 64b0a60..0003b1e 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -2422,7 +2422,7 @@ AddressSpace *address_space_init_shareable(MemoryRegion 
> *root, const char *name)
>      AddressSpace *as;
>  
>      QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) {
> -        if (root == as->root && as->malloced) {
> +        if (root == as->root && as == &address_space_memory) {

Of course you need to keep the as->malloced check, don't you?

>              as->ref_count++;
>              return as;
>          }
> 

This is not really beautiful, but compared to v1 and v2 it has the advantage 
that it works (with the as->malloced check reintroduced).
Peter, you introduced address_space_init_shareable, what do you think?

Paolo