From a7f19c79e30b6e4e83353605341abdccc29d27b4 Mon Sep 17 00:00:00 2001 From: Michael Chastain Date: Thu, 21 Aug 2003 19:55:32 +0000 Subject: [PATCH] 2003-08-21 Michael Chastain * symtab.h: Add doco on the space critical structures and some measurements of space usage. --- gdb/ChangeLog | 5 +++++ gdb/symtab.h | 52 ++++++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 54 insertions(+), 3 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 2d82dc9e720..28007db694f 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2003-08-21 Michael Chastain + + * symtab.h: Add doco on the space critical structures and + some measurements of space usage. + 2003-08-21 Michael Snyder * tracepoint.c (trace_dump_command): Trace break address diff --git a/gdb/symtab.h b/gdb/symtab.h index a7f1e30ecd3..da301254749 100644 --- a/gdb/symtab.h +++ b/gdb/symtab.h @@ -35,13 +35,55 @@ struct blockvector; struct axs_value; struct agent_expr; +/* Some of the structures in this file are space critical. + The space-critical structures are: + + struct general_symbol_info + struct symbol + struct partial_symbol + + These structures are layed out to encourage good packing. + They use ENUM_BITFIELD and short int fields, and they order the + structure members so that fields less than a word are next + to each other so they can be packed together. */ + +/* Rearranged: used ENUM_BITFIELD and rearranged field order in + all the space critical structures (plus struct minimal_symbol). + Memory usage dropped from 99360768 bytes to 90001408 bytes. + I measured this with before-and-after tests of + "HEAD-old-gdb -readnow HEAD-old-gdb" and + "HEAD-new-gdb -readnow HEAD-old-gdb" on native i686-pc-linux-gnu, + red hat linux 8, with LD_LIBRARY_PATH=/usr/lib/debug, + typing "maint space 1" at the first command prompt. + + Here is another measurement (from andrew c): + # no /usr/lib/debug, just plain glibc, like a normal user + gdb HEAD-old-gdb + (gdb) break internal_error + (gdb) run + (gdb) maint internal-error + (gdb) backtrace + (gdb) maint space 1 + + gdb gdb_6_0_branch 2003-08-19 space used: 8896512 + gdb HEAD 2003-08-19 space used: 8904704 + gdb HEAD 2003-08-21 space used: 8396800 (+symtab.h) + gdb HEAD 2003-08-21 space used: 8265728 (+gdbtypes.h) + + The third line shows the savings from the optimizations in symtab.h. + The fourth line shows the savings from the optimizations in + gdbtypes.h. Both optimizations are in gdb HEAD now. + + --chastain 2003-08-21 */ + + + /* Define a structure for the information that is common to all symbol types, including minimal symbols, partial symbols, and full symbols. In a multilanguage environment, some language specific information may need to - be recorded along with each symbol. + be recorded along with each symbol. */ - These fields are ordered to encourage good packing, since we frequently - have tens or hundreds of thousands of these. */ +/* This structure is space critical. See space comments at the top. */ struct general_symbol_info { @@ -557,6 +599,8 @@ struct alias_list struct alias_list *next; }; +/* This structure is space critical. See space comments at the top. */ + struct symbol { @@ -638,6 +682,8 @@ struct symbol on a partial symtab list and which points to the corresponding normal symtab once the partial_symtab has been referenced. */ +/* This structure is space critical. See space comments at the top. */ + struct partial_symbol { -- 2.30.2