Bug 38368 – When FastMalloc Returns memory often left with lots of small spans

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Stephanie Lewis]

When FastMalloc Returns memory we're often left with lots of 1 page spans and none of the large sizes.  Change the scavenging algorithm to always keep some large size spans around.  Also change it distribute the returns among the list more equally. 
<rdar://problem/7834433> REGRESSSION: 1.5% PLT regression due to 56028 (return memory quicker).

[Stephanie Lewis]

Created attachment 54775 [details]
patch

Attaching Patch.

[Eric Seidel (no email)]

Attachment 54775 [details] did not build on mac:
Build output: http://webkit-commit-queue.appspot.com/results/1792206

[WebKit Review Bot]

Attachment 54775 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style', '--no-squash']" exit_code: 1
JavaScriptCore/wtf/FastMalloc.cpp:1281:  Missing spaces around /  [whitespace/operators] [3]
JavaScriptCore/wtf/FastMalloc.cpp:1546:  Extra space before )  [whitespace/parens] [2]
Total errors found: 2 in 2 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Stephanie Lewis]

Created attachment 54776 [details]
second patch

fixed some issues.

[Eric Seidel (no email)]

Attachment 54776 [details] did not build on mac:
Build output: http://webkit-commit-queue.appspot.com/results/1935031

[Eric Seidel (no email)]

Comment on attachment 54776 [details]
second patch

The EWS thinks this will break leopard:
fzzgiiisjukfwleasczjmdxaevcz/JavaScriptCorePrefix.h -c /Users/eseidel/Projects/MacEWS/JavaScriptCore/wtf/FastMalloc.cpp -o /Users/eseidel/Projects/MacEWS/WebKitBuild/JavaScriptCore.build/Release/JavaScriptCore.build/Objects-normal/i386/FastMalloc.o
cc1plus: warnings being treated as errors
/Users/eseidel/Projects/MacEWS/JavaScriptCore/wtf/FastMalloc.cpp:1281: warning: implicit conversion shortens 64-bit value into a 32-bit value
/Users/eseidel/Projects/MacEWS/JavaScriptCore/wtf/FastMalloc.cpp: In member function ‘void WTF::TCMalloc_PageHeap::scavenge()’:
/Users/eseidel/Projects/MacEWS/JavaScriptCore/wtf/FastMalloc.cpp:1546: warning: implicit conversion shortens 64-bit value into a 32-bit value
distcc[85602] ERROR: compile /Users/eseidel/Projects/MacEWS/JavaScriptCore/wtf/FastMalloc.cpp on localhost failed

[Stephanie Lewis]

Created attachment 54841 [details]
patch with correct fix

and now it builds on 32bit

[Geoffrey Garen]

Comment on attachment 54841 [details]
patch with correct fix

I think the "l" postfix is wrong, since it will give you a long where you want a floating point number. The simplest way to appease the 64-bit warning is probably to use float, since it's 32-bit.

[Stephanie Lewis]

Created attachment 54971 [details]
patch

one more time

[Geoffrey Garen]

Comment on attachment 54971 [details]
patch

r=me

You can just declare "j" to be size_t, to avoid the static_cast.

[Stephanie Lewis]

Committed http://trac.webkit.org/changeset/58730