[webkit-dev] DocumentLoader::m_mainResourceData seems no need

[Xianzhu Wang]

On Tue, Aug 16, 2011 at 3:41 PM, Pavel Feldman <pfeldman at chromium.org>wrote:

> On Tue, Aug 16, 2011 at 11:20 AM, Xianzhu Wang <phnixwxz at gmail.com> wrote:
>
>> Hi,
>>
>> I found that DocumentLoader will hold m_mainResourceData during its whole
>> life. I'm wondering if this is necessary. I searched all callers of
>> DocumentLoader::mainResourceData() and DocumentLoader::mainResource() and
>> they seem all called before or just after the document is loaded.
>>
>
> This is not the case for the inspector and a number of other usages I can
> see here:
>
> http://codesearch.google.com/codesearch#search/&exact_package=chromium&q=mainResourceData%5C(%5C)&type=cs
>

Thanks. I missed some cases (like WebKit2 and WebDataSource ones) as I only
searched the compiled files in my environment. And I did overlooked the
first case in inspector.


> "just after" might be problematic to define as well.
>

I meant "just after" that the function is called from somewhere
xxxDidFinishLoading() etc. For these cases, by carefully adjust the
sequence, we can let them depend on DocumentLoader::m_mainResourceLoader
instead of m_mainResourceData.

An (maybe incomplete) list of cases that might use
DocumentLoader::mainResourceData() after loading is:
  WebDataSource::data()
  WebKit::WebFrame::source()
  WebKit::WebPage::getMainResourceDataOfFrame()
  InspectorPageAgent::resourceContent()

As the amount of memory saved by removing m_mainResourceData could be
significant on mobile devices, for these cases I think it might be
reasonable to have some constraints on particular platforms. For example,
use an alternative way like fetching from cache, reloading, etc., or simply
don't support them.


> Regards
> Pavel
>
>  If we remove DocumentLoader::m_mainResourceData, the main resource data
>> could be freed if there is no other references (seems true if the page is
>> not inspected) and will save memory.
>>
>> I tried to removing DocumentLoader::m_mainResourceData and run all layout
>> tests in chromium-linux. I got 6 text mismatches and 1 timeout and will
>> investigate the failures.
>>
>> However, can anyone describe the original intent of
>> DocumentLoader::m_mainResourceData? What's the case that it is used after
>> the document is loaded?
>>
>> Thanks,
>> Xianzhu
>>
>>
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>>
>>
>
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