Re: [RFA 08/15] Remove readin and compunit_symtab fields from psymtab

Tom Tromey
2018-10-06T01:24:57Z

>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:
Simon> As Pedro pointed out a few times, unordered_map is an hash map with open
Simon> hashing. So we change what was previously a single pointer dereference
Simon> to a lookup in a hash table, followed with a linear search in a linked
Simon> list. If this map is looked up very frequently, maybe we should consider
Simon> using an htab_t instead? Some profiling data would help, but it seems
Simon> like psymtab_read_in_p is called quite a bit when looking up symbols...

[...]

Tom> I still haven't tried any performance measurements.
Tom> I'm not quite sure what to try.

I ran the gdb.perf tests and on some tests, it seems that the results
are within the noise; but on backtrace (2048) and skip-function-3000 (4000)
gdb is about 4% slower. I don't know if this is enough to worry about.

Tom