Bug 50412 – http://www.wunderground.com/US/CA/Hayward.html causes big memory spike during page loading

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Antti Koivisto]

http://www.wunderground.com/US/CA/Hayward.html causes big memory spike (>60MB) during page loading.

The memory i used under this stack:

#0  JSC::JSString::resolveRope (this=0x107cdaa0, exec=0x131b5098) at /Users/antti/jasper/webkit/JavaScriptCore/runtime/JSString.cpp:46
#1  0x00390821 in JSC::JSString::value (this=0x107cdaa0, exec=0x131b5098) at JSString.h:327
#2  0x004ca677 in JSC::JSValue::toThisString (this=0xb01ca590, exec=0x131b5098) at JSObject.h:731
#3  0x004c7978 in JSC::stringProtoFuncSubstr (exec=0x131b5098, thisValue={m_ptr = 0x107cdaa0}, args=@0xb01ca728) at /Users/antti/jasper/webkit/JavaScriptCore/runtime/StringPrototype.cpp:728
#4  0x00420743 in JSC::Interpreter::privateExecute (this=0x9855200, flag=JSC::Interpreter::Normal, registerFile=0x985520c, callFrame=0x131b505c, e

[Antti Koivisto]

Created attachment 75418 [details]
avoid flattening ropes when creating substrings

Creating a substring caused the original string be flattened if it was in the rope form. This could use significant amount of memory by reducing buffer sharing between strings.
        
Add a rope specific substring function that constructs the substring by reusing the rope fibers instead of flattening the rope.
        
No change observed in SunSpider.

[Darin Adler]

Gavin, you should review this!

[Antti Koivisto]

<rdar://problem/8135782>

[Early Warning System Bot]

Attachment 75418 [details] did not build on qt:
Build output: http://queues.webkit.org/results/6851004

[Antti Koivisto]

Created attachment 75426 [details]
fix build

[Build Bot]

Attachment 75418 [details] did not build on win:
Build output: http://queues.webkit.org/results/6811012

[Gavin Barraclough]

Comment on attachment 75426 [details]
fix build

r+.

This looks good to me, but please fix up the existing use of int instead of unsigned for the string length, & remove associated casts.

[Antti Koivisto]

http://trac.webkit.org/changeset/73433