[Bug gdb/12332] Provide efficient source lookup for use by IDE

["jan.kratochvil at redhat dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=12332

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

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                 CC|                            |jan.kratochvil at redhat
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--- Comment #1 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2011-02-25 22:56:20 UTC ---
I (briefly) read through the Eclipse Bug but I do not see any indication the
filesystem lookup would be slow.
In fact since Linux kernel dcache (linux-2.1.x or so) any pathname lookups are
blazingly fast:
find $PWD -type f|tr -cd /|wc -c
 = 279751 = directory components for lookup
find $PWD -type f|wc -l
 = 26239 = files = number of breakpoints
time sh -c 'find $PWD -type f|xargs /bin/ls|wc -l'
real 0m0.903s = the overhead of any lookups is really negligible
[ kernel-debug-2.6.35.11-83.fc14.x86_64, i7-920, ext3 fs, second run ]

If you mean slowness on the first run (and on the second run it is already
fast) then it is by the disk access.  But not looking up the leading
directories would not help it as those are already in dcache even in such case.

I would rather bet the slowness is in GDB itself, it has problems handling
1000+ breakpoints even on high-end hardware.  I rather did not expect anyone
would use so many breakpoints.

I already did one breakpoints performance improvement which made the 1000
breakpoints case acceptable again (although it is still far from perfect):
http://sourceware.org/ml/gdb-patches/2009-10/msg00289.html

I would like to see some oprofile or gprof results first before deciding which
part to fix.

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