* [Qemu-devel] [PATCH] memory: reduce heap Rss size around 3M
@ 2017-03-08 15:11 Yang Zhong
2017-03-08 11:17 ` Philippe Mathieu-Daudé
0 siblings, 1 reply; 3+ messages in thread
From: Yang Zhong @ 2017-03-08 15:11 UTC (permalink / raw)
To: qemu-devel; +Cc: pbonzini, anthony.xu, Yang Zhong
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 <yang.zhong@intel.com>
---
memory.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/memory.c b/memory.c
index 284894b..799ca4c 100644
--- a/memory.c
+++ b/memory.c
@@ -2422,8 +2422,10 @@ 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) {
- as->ref_count++;
+ if (root == as->root) {
+ if (as->malloced) {
+ as->ref_count++;
+ }
return as;
}
}
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [Qemu-devel] [PATCH] memory: reduce heap Rss size around 3M
2017-03-08 15:11 [Qemu-devel] [PATCH] memory: reduce heap Rss size around 3M Yang Zhong
@ 2017-03-08 11:17 ` Philippe Mathieu-Daudé
2017-03-09 16:34 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Philippe Mathieu-Daudé @ 2017-03-08 11:17 UTC (permalink / raw)
To: Yang Zhong, qemu-devel; +Cc: pbonzini, anthony.xu
On 03/08/2017 12:11 PM, 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 <yang.zhong@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> memory.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/memory.c b/memory.c
> index 284894b..799ca4c 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -2422,8 +2422,10 @@ 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) {
> - as->ref_count++;
> + if (root == as->root) {
> + if (as->malloced) {
> + as->ref_count++;
> + }
> return as;
> }
> }
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Qemu-devel] [PATCH] memory: reduce heap Rss size around 3M
2017-03-08 11:17 ` Philippe Mathieu-Daudé
@ 2017-03-09 16:34 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2017-03-09 16:34 UTC (permalink / raw)
To: Philippe Mathieu-Daudé, Yang Zhong, qemu-devel; +Cc: anthony.xu
On 08/03/2017 12:17, Philippe Mathieu-Daudé wrote:
> On 03/08/2017 12:11 PM, 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 <yang.zhong@intel.com>
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>
>> ---
>> memory.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/memory.c b/memory.c
>> index 284894b..799ca4c 100644
>> --- a/memory.c
>> +++ b/memory.c
>> @@ -2422,8 +2422,10 @@ 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) {
>> - as->ref_count++;
>> + if (root == as->root) {
>> + if (as->malloced) {
>> + as->ref_count++;
>> + }
>> return as;
>> }
>> }
>>
This is wrong. If as->malloced is false, the AddressSpace might be
embedded in another struct. This other struct could be freed when
as->ref_count is still greater than 0, causing a use-after-free bug.
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-03-08 15:11 [Qemu-devel] [PATCH] memory: reduce heap Rss size around 3M Yang Zhong
2017-03-08 11:17 ` Philippe Mathieu-Daudé
2017-03-09 16:34 ` Paolo Bonzini
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