Bug 85258

Summary: Early-out for subtracting a non-intersecting region
Product: WebKit Reporter: Dana Jansens <danakj>
Component: New BugsAssignee: Dana Jansens <danakj>
Status: RESOLVED FIXED    
Severity: Normal CC: andersca, backer, darin, enne, jamesr, piman, vangelis, webkit.review.bot
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
Patch none

Dana Jansens
Reported 2012-04-30 21:15:40 PDT
Early-out for subtracting a non-intersecting region
Attachments
Patch (1.41 KB, patch)
2012-04-30 21:20 PDT, Dana Jansens 		no flags
DetailsFormatted DiffDiff
View All Add attachment proposed patch, testcase, etc.
Dana Jansens
Comment 1 2012-04-30 21:20:02 PDT
Created attachment 139578 [details] Patch
Hajime Morrita
Comment 2 2012-05-01 02:05:59 PDT
Comment on attachment 139578 [details] Patch Harvest all low hanging fruits!!
WebKit Review Bot
Comment 3 2012-05-01 02:14:28 PDT
Comment on attachment 139578 [details] Patch Clearing flags on attachment: 139578 Committed r115716: <http://trac.webkit.org/changeset/115716>
WebKit Review Bot
Comment 4 2012-05-01 02:14:33 PDT
All reviewed patches have been landed. Closing bug.
Darin Adler
Comment 5 2012-05-01 13:14:18 PDT
Is this change for better performance or is it related to correctness? If it’s for better performance, what test demonstrates the improvement? How good is the improvement?
Dana Jansens
Comment 6 2012-05-01 13:32:20 PDT
It is for performance, if you subtract a Region that does not intersect, you would make a memcpy of the orignal region. Region copies are showing themselves to be very costly, you can see some backstory here https://bugs.webkit.org/show_bug.cgi?id=81076 I must confess I'm not sure what you mean by a test though, we use unit tests and layout tests to verify correctness, but I've never been asked to write a test to show performance differences.
Darin Adler
Comment 7 2012-05-01 13:37:02 PDT
Most performance-driven changes include information about some kind of performance test and data about the results before and after the code change. I can find you examples if you haven’t seen that in the WebKit project before.
Dana Jansens
Comment 8 2012-05-01 13:43:53 PDT
Sure, I'd love a good example, thanks.
Darin Adler
Comment 9 2012-05-02 12:27:05 PDT
I’m not sure these are the best examples, but three I found with a quick search are these: http://trac.webkit.org/changeset/114912 http://trac.webkit.org/changeset/114351 http://trac.webkit.org/changeset/112387
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