[webkit-dev] improving String::append()
mjs at apple.com
Thu Dec 3 10:01:42 PST 2009
On Dec 3, 2009, at 8:32 AM, Zoltan Herczeg wrote:
> according to my measurements, a large chunk of WebKit memory
> comes from WebCore::TextResourceDecoder::decode
> (loader/TextResourceDecoder.cpp:818) which calls String::append
> (String.cpp:82). The comment there says:
> // FIXME: This is extremely inefficient.
> I would volunteer to rewrite the code (especially reducing the memory
> consumption), but first, I would like to hear your opinion how can
> we make
> the string handling of WebKit better.
I believe the inefficiency there is speed, not space. Vector<UChar> or
StringBuilder as an alternative would reduce potential for excess
reallocation but I don't think they would reduce memory use. In fact
memory use may go up. (As a side note I was unable to find the
String::append call in TextResourceDecoder.
I think a lot of memory use is blamed on the decoder because we keep
around a decoded copy of every text-based subresource. In theory we
could drop the decoded version under memory pressure since it can be
re-decoded from the original data on demand.
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