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From: "dje at google dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug symtab/15412] New: Performance regression in "info
 {func,var,types} foo" (mostly info types).
Date: Sat, 27 Apr 2013 21:34:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id=15412

             Bug #: 15412
           Summary: Performance regression in "info {func,var,types} foo"
                    (mostly info types).
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: symtab
        AssignedTo: unassigned@sourceware.org
        ReportedBy: dje@google.com
    Classification: Unclassified


In a large program I'm seeing a performance regression in
info {func,var,types} ^foo::(anonymous namespace)

For example, in 7.5 it takes 2 seconds, in 7.6 and cvs head it takes ~300
seconds.

I think there are multiple factors here because a comparison of gdb
before/after the type-pretty-printing patches of ~2012-11-12 I only see a perf
degradation from 2 seconds to 150 seconds.  So something after that is then
slowing things down from 150s to 300s.

Data point: If I hack "info {func,var,type}" to set type_print_options.raw = 1,
I get most (maybe all) the performance back.

It seems like we want type-pretty-printing for info types, but the performance
cost can be high.  Thus I'm thinking "info {func,var,types}" should have a /r
(raw) option.

OTOH, a lot of the cost can be reduced, I think, by caching lookups: the same
symbol is processed many(!!!) times.  The caching could be at multiple levels
(e.g., more than just simple symbol lookups), I'm not sure what's the best one
yet.

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