Re: [PATCH] Have partial symbol tables own psymbol vectors

Tom Tromey
2020-09-01T14:20:07Z

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:

Simon> On 2020-08-31 1:09 p.m., Tom Tromey wrote:
>> The main drawback of this patch is that it increases the size of
>> partial symtab.

Simon> Regarding this: it seems to me like in the end, no more memory is used (even when
Simon> sharing partial symtabs between objfiles), it's just moved around, is that right?
Simon> If so, I don't understand why you say it's a "drawback", doesn't it make it sound
Simon> a bit scarier than it actually is?

No, a bit more memory is used.

Right now there are 2 std::vector<>s used for globals and static. (And
there is a pair used to track the vectors being updated.)

Each partial symtab currently has integer indexes into these vectors.

After the patch, the vectors are removed from the psymtab storage (this
is per-objfile, so IMO negligible), but now each partial symtab holds
two vectors. On my machine (x86-64 with GNU libstdc++), a std::vector<>
is 24 bytes. So, we're going from 4*sizeof(int) == 16 bytes per partial
symtab to 48 bytes per.

Tom