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IDProjectCategoryView StatusLast Update
0002366NetSurfJavascriptpublic2016-02-16 14:13
ReporterHarriet Bazley 
Assigned ToMichael Drake 
PlatformARMOSRISC OSOS Version5.19
Product Version3.4 
Target VersionFixed in Version3.4 
Summary0002366: JS lockup
DescriptionPage https://1940sexperiment.wordpress.com/ goes into single-tasking loop with JavaScript enabled. (Stuck on the Fetching, Fetching, Processing stage with desktop unresponsive.)
Additional InformationIyonix Aria, RISC OS 5.20
TagsNo tags attached.
Fixed in CI build #3032
Reported in CI build #3000
URL of problem pagehttps://1940sexperiment.wordpress.com/
Attached Files

has duplicate 0002364closedMichael Drake JavaScript-related lockup 
has duplicate 0002348closed Looping 

Vincent Sanders


Vincent Sanders (administrator)

(1.340669) content/content.c:82 content__init: url https://s1.wp.com/_static/??-eJyVzTEOwjAMheELYaxCQCyIs6SNCS6uGzkuFbenCwNLUaenf/j0cC7QjeqkjsMERabMWtFndieDVmL3bNkSFCZUepGRJta87+sOt9jy37FQghx -> 0x2c0c7d0
(1.340682) content/content.c:664 content_add_user: content https://s1.wp.com/_static/??-eJyVzTEOwjAMheELYaxCQCyIs6SNCS6uGzkuFbenCwNLUaenf/j0cC7QjeqkjsMERabMWtFndieDVmL3bNkSFCZUepGRJta87+sOt9jy37FQghx (0x2c0c7d0), user 0x4db240 0x2b7f4e0
(1.340703) content/content.c:282 content_convert: content https://s1.wp.com/_static/??-eJyVzTEOwjAMheELYaxCQCyIs6SNCS6uGzkuFbenCwNLUaenf/j0cC7QjeqkjsMERabMWtFndieDVmL3bNkSFCZUepGRJta87+sOt9jy37FQghx (0x2c0c7d0)
(1.340714) render/html_script.c:273 convert_script_sync_cb: script 27 done 'https://s1.wp.com/_static/??-eJyVzTEOwjAMheELYaxCQCyIs6SNCS6uGzkuFbenCwNLUaenf/j0cC7QjeqkjsMERabMWtFndieDVmL3bNkSFCZUepGRJta87+sOt9jy37FQghxFyN6/taLKWB3uEtmwPqItF99d0G24NiGE5nQ+HC/9B5XxV+w='
(1.340720) render/html_script.c:275 convert_script_sync_cb: 0 fetches active
(7.355472) javascript/duktape/dukky.c:376 js_exec: Uncaught error in JS: ReferenceError: identifier 'jQuery' undefined
(7.355498) javascript/duktape/dukky.c:378 js_exec: was at: javascript/duktape/dukky.c line 1
(7.355504) javascript/duktape/dukky.c:379 js_exec: Stack trace: ReferenceError: identifier 'jQuery' undefined
    eval javascript/duktape/dukky.c:1 preventsyield
(7.355551) render/html_script.c:532 html_process_script: content 0x2c06690 parser 0x2c06c30 node 0x2b50a90
(7.355668) javascript/duktape/dukky.c:383 js_exec: Returning false
(7.355692) render/html_script.c:532 html_process_script: content 0x2c06690 parser 0x2c06c30 node 0x2b83860
Vincent Sanders


Vincent Sanders (administrator)

It does not appear to hang, just takes some time to run the javascript
Michael Drake


Michael Drake (administrator)

Last edited: 2015-10-21 21:26

View 2 revisions

Uploaded a kcachegrind profile; duktape-unicode-regex.png

As I understand it duktape's implementation of Unicode case insensitive regular expressions is written for low memory usage, rather than for speed.

As such its taking almost 90% of the time to start NetSurf with that page just to do the regular expressions. In the remaining 10% of the time NetSurf starts, decodes all the html and css, generates the dom, does all the non-regex javascript, selects styles for all the elements, lays out the page, renders it, decodes the images and renders them, and then quits.

So there's a lot of room for improvement. We've already reported the issue upstream to the duktape maintainer.

Michael Drake


Michael Drake (administrator)

Last edited: 2015-10-24 13:48

View 2 revisions

From the duktape maintainer:

< svaarala_> tlsa: thanks - i'll try to figure out a minimal fix for this issue as soon as i get some free time
< svaarala_> tlsa: a more comprehensive solution would be to provide a speed optimized unicode implementation in general, but this particular case is much worse than other places
< svaarala_> tlsa: actually, i wrote a quick branch which uses a 64k entry lookup for the regexp canonicalization
< svaarala_> tlsa: the cost is 128kB of footprint but it makes a 30 second pathological test run in 30ms
< svaarala_> tlsa: i don't plan on this being the long term solution but this might fix your immediate issue if that 128k is not too much?
< svaarala_> tlsa: anyway, if you're interested, i'll push the test branch and it'd then be interesting to know if that fixes the netsurf issue
< svaarala_> tlsa: at the very least it'd tell us that this is the only real problem in those cases
< svaarala_> tlsa: here's a snapshot with a prototype fix included: http://duktape.org/snapshots/duktape-1.3.99-20151022195439-v1.3.0-138-g4045393-regexp-canonicalize-lookup.tar.xz
< svaarala_> tlsa: and here's the pull: https://github.com/svaarala/duktape/pull/411

Michael Drake


Michael Drake (administrator)

Using the prototype duktape fix, the performance is much better. Most of the time is still spent processing javascript, but its not dominated by regex work.

I've attached another profile image which shows the improvement: duktape-fast-regex.png

From the 2 images we can see the total instruction fetch cost is reduced to 12% of what it was (from 60 billion to 7 billion).
Michael Drake


Michael Drake (administrator)

Fixed by http://git.netsurf-browser.org/netsurf.git/commit/?id=c22706b9049c4c85205a8cc9a3dc72a4e4a52be5
Harriet Bazley


Harriet Bazley (reporter)

This problem seems to have reappeared after I upgraded from v3222 to 3244.
Michael Drake


Michael Drake (administrator)

Fixed in 3250, thanks.
Vincent Sanders


Vincent Sanders (administrator)

Confirmed fixed in 3.4 release

-Issue History
Date Modified Username Field Change
2015-10-18 16:49 Harriet Bazley New Issue
2015-10-20 20:58 Vincent Sanders Status new => acknowledged
2015-10-20 20:58 Vincent Sanders Product Version => 3.4
2015-10-21 20:07 Vincent Sanders Note Added: 0000974
2015-10-21 20:08 Vincent Sanders Note Added: 0000975
2015-10-21 21:07 Michael Drake File Added: duktape-unicode-regex.png
2015-10-21 21:14 Michael Drake Note Added: 0000976
2015-10-21 21:16 Michael Drake Status acknowledged => confirmed
2015-10-21 21:26 Michael Drake Note Edited: 0000976 View Revisions
2015-10-24 13:47 Michael Drake Note Added: 0000979
2015-10-24 13:48 Michael Drake Note Edited: 0000979 View Revisions
2015-10-24 13:49 Michael Drake File Added: duktape-fast-regex.png
2015-10-24 13:55 Michael Drake Note Added: 0000980
2015-10-30 14:09 Vincent Sanders Relationship added has duplicate 0002364
2015-10-31 18:24 Michael Drake Fixed in CI build # => 3032
2015-10-31 18:24 Michael Drake Assigned To => Michael Drake
2015-10-31 18:24 Michael Drake Status confirmed => resolved
2015-10-31 18:24 Michael Drake Resolution open => fixed
2015-10-31 18:24 Michael Drake Fixed in Version => 3.4
2015-10-31 18:25 Michael Drake Note Added: 0001005
2015-10-31 18:46 Vincent Sanders Relationship added has duplicate 0002348
2016-01-02 23:19 Harriet Bazley Note Added: 0001133
2016-01-02 23:19 Harriet Bazley Status resolved => feedback
2016-01-02 23:19 Harriet Bazley Resolution fixed => reopened
2016-01-05 13:37 Michael Drake Note Added: 0001137
2016-01-05 13:37 Michael Drake Status feedback => resolved
2016-01-05 13:37 Michael Drake Resolution reopened => fixed
2016-02-16 14:13 Vincent Sanders Note Added: 0001249
2016-02-16 14:13 Vincent Sanders Status resolved => closed
+Issue History