481793 - TM: Better coordination of nested tree recording

Status: VERIFIED FIXED

(Core :: JavaScript Engine, defect)

Description

[Andreas Gal :gal]

The attached patch improves the coordination of nested tree recording. When we abort an outer recorder because we wait for a) an inner tree to be compiled b) an inner tree to finish growing a branch or c) an inner tree to grow around its inner tree, remember in that recording the loop header of the loop we just aborted, and in case that compilation succeeds, permit all peer fragments attached to that particular loop header to compile at least one more time. If the location was permanently blacklisted, undo the blacklisting. With this patch we can drop BL_ATTEMPTS to 2 (from 6) and still get proper tree construction for our favorite trouble makers fasta and fannkuch. This wins about 10ms on SS and should overall reduce the recording overhead in cases where we abort recording repeatedly since we blacklist faster now.

Comment 1

[Andreas Gal :gal]

Attachment: patch

Comment 2

[Andreas Gal :gal]

Note also this subtle change:

int32_t& hits = c->hits();
    if (outer || hits++ >= HOTEXIT && hits <= HOTEXIT+MAXEXIT) {
        /* start tracing secondary trace from this point */
        c->lirbuf = f->lirbuf;

dmandelin identified this problem. We used to wait for HOTEXIT when an already recorded inner tree tried to grow a branch while we were recording the outer tree. This caused repeated recording aborts. If we already abort recording because of such an inner tree growth, we of course want to immediately record no matter what hotexit says.

Comment 3

[David Mandelin [:dmandelin]]

Comment on attachment 365815 [details] [diff] [review]
patch

Looks good to me. I'll do my own SS test on it a bit later (since my machine tends to be different) but I think it's good to land based on what we know.

Comment 4

[Andreas Gal :gal]

http://hg.mozilla.org/tracemonkey/rev/ec90dd58f1da

Comment 5

[Robert Sayre]

http://hg.mozilla.org/mozilla-central/rev/ec90dd58f1da

Comment 6

[Bob Clary [:bc] (inactive)]

http://hg.mozilla.org/tracemonkey/rev/3fb1b5d6dc60
/cvsroot/mozilla/js/tests/js1_8_1/trace/trace-test.js,v  <--  trace-test.js
new revision: 1.13; previous revision: 1.12

Comment 7

[Robert Sayre]

http://hg.mozilla.org/releases/mozilla-1.9.1/rev/8644a9f87bdc

Comment 8

[Bob Clary [:bc] (inactive)]

v 1.9.1, 1.9.2