Re: [Qemu-devel] [PATCH] page_cache: dup memory on insert

[Peter Lieven]

Am 25.02.2013 um 13:15 schrieb Orit Wasserman <address@hidden>:

> Hi Peter,
> Now I get the previous patch, it should have been a patch series :).
> The reason we allocate from outside of the page cache is because of 
> cache_resize
> that also uses cache_insert but doesn't duplicate the buffer.
> There is no memory leak because if the page is cached we don't call 
> cache_insert
> but do memcpy instead.

Ah ok, haven't noticed the resize case. But there is still a men leak on a 
simple collision (first patch) - nothing
to do with resize.

We should discuss if the page cache frees data it should also allocate the 
data. Maybe we need to different functions.

Peter


> 
> Regards,
> Orit
> On 02/25/2013 01:52 PM, Peter Lieven wrote:
>> The page cache frees all data on finish, on resize and
>> if there is collision on insert. So it should be the caches
>> responsibility to dup the data that is stored in the cache.
>> 
>> Signed-off-by: Peter Lieven <address@hidden>
>> ---
>> arch_init.c                    |    3 +--
>> include/migration/page_cache.h |    3 ++-
>> page_cache.c                   |    2 +-
>> 3 files changed, 4 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch_init.c b/arch_init.c
>> index 8da868b..97bcc29 100644
>> --- a/arch_init.c
>> +++ b/arch_init.c
>> @@ -293,8 +293,7 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t 
>> *current_data,
>> 
>>     if (!cache_is_cached(XBZRLE.cache, current_addr)) {
>>         if (!last_stage) {
>> -            cache_insert(XBZRLE.cache, current_addr,
>> -                         g_memdup(current_data, TARGET_PAGE_SIZE));
>> +            cache_insert(XBZRLE.cache, current_addr, current_data);
>>         }
>>         acct_info.xbzrle_cache_miss++;
>>         return -1;
>> diff --git a/include/migration/page_cache.h b/include/migration/page_cache.h
>> index 3839ac7..87894fe 100644
>> --- a/include/migration/page_cache.h
>> +++ b/include/migration/page_cache.h
>> @@ -57,7 +57,8 @@ bool cache_is_cached(const PageCache *cache, uint64_t 
>> addr);
>> uint8_t *get_cached_data(const PageCache *cache, uint64_t addr);
>> 
>> /**
>> - * cache_insert: insert the page into the cache. the previous value will be 
>> overwritten
>> + * cache_insert: insert the page into the cache. the page cache
>> + * will dup the data on insert. the previous value will be overwritten
>>  *
>>  * @cache pointer to the PageCache struct
>>  * @addr: page address
>> diff --git a/page_cache.c b/page_cache.c
>> index a6c3a15..e670d91 100644
>> --- a/page_cache.c
>> +++ b/page_cache.c
>> @@ -158,7 +158,7 @@ void cache_insert(PageCache *cache, uint64_t addr, 
>> uint8_t *pdata)
>>         g_free(it->it_data);
>>     }
>> 
>> -    it->it_data = pdata;
>> +    it->it_data = g_memdup(pdata, cache->page_size);
>>     it->it_age = ++cache->max_item_age;
>>     it->it_addr = addr;
>> }
>