355805 - js_GetSrcNote is O(N^2)

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Boris Zbarsky [:bzbarsky]]

STEPS TO REPRODUCE:

1) Enable JS strict warnings
2) Load http://mail.mozilla.com (or probably any other Zimbra page).
3) Observe the hang.
4) Profile it.

EXPECTED RESULTS: No hang, hence nothing to profile

ACTUAL RESULTS:
  Total hit count: 206039
  Count %Total  Function Name
  125273   60.8     js_GetSrcNote
  66450   32.3     js_SrcNoteLength

Brendan sez:

<brendan> yes, js_GetSrcNote has O(n^2) growth
<brendan> know bug, wanted to fix it for 1.9alpha

The JS file in question (Zimbra's Ajax_all.asc) is 600-some KB.

Comment 1

[Brendan Eich [:brendan]]

I think this is a dup of bug 347306.

/be

Comment 2

[Brendan Eich [:brendan]]

Patch that fixes the O(n^2) problem for typical lookup patterns is now attached in bug 346306.

/be

Comment 3

[Jesse Ruderman]

bz, did the fix for bug 347306 make the Zimbra hang go away?

Comment 4

[:Gavin Sharp [email: [e-mail]]]

(In reply to comment #3)
> bz, did the fix for bug 347306 make the Zimbra hang go away?

I was seeing the Zimbra hang too (due to strict warnings being enabled), and bug 347306 fixed it for me.

Comment 5

[Boris Zbarsky [:bzbarsky]]

OK, hang is down from "forever" to "15 seconds or so".  Marking fixed; I'll file a followup on the remaining perf issues.

Comment 6

[Brendan Eich [:brendan]]

js_SrcNoteLength was never a problem, because note arity is <= 3.

/be

Comment 7

[Boris Zbarsky [:bzbarsky]]

> js_SrcNoteLength was never a problem

That's not what jprof said.  Unless it was simply in the profile because of the large number of calls from js_GetSrcNote?

I filed bug 355951 on the remaining issue.

Comment 8

[Brendan Eich [:brendan]]

(In reply to comment #7)
> > js_SrcNoteLength was never a problem
> 
> That's not what jprof said.  Unless it was simply in the profile because of the
> large number of calls from js_GetSrcNote?

Yes.

/be